International Society of Arachnology |
J. Adis1, J. Cokendolpher2, J. Reddell3 and J.M.G. Rodrigues4 1Max-Planck-Institute for Limnology, Tropical Ecology Working Group, Postfach l65, D-24302 Plön, Germany; (adis@mpil-ploen.mpg.de); 22007 29th St., Lubbock/Texas 79411, USA; (cokendolpher@aol.com); 3Texas Memorial Museum, University of Texas, Austin/Texas 78705, USA; (jreddell.caves@mail.utexas.edu); 4Instituto Nacional de Pesquisas da Amazénia (INPA), C.P. 478, 69.011-970 Manaus/AM, Brazil; (jmaria@inpa.gov.br)
Abundance and phenology of Schizomida (Arachnida) from a secondary upland forest in central Amazonia
The 357 Schizomida (shorttailed whipscorpions) collected within 12 months in the soil (0-7 cm depth) of a secondary upland forest (60.4 é 32.2 ind./m2/month) near Manaus were represented by Surazomus mirim Cokendolpher and Reddell, 2000 and S. rodriguesi Cokendolpher and Reddell, 2000 (99.7% and 0.3% of the total catch, respectively). About 74% of all specimens of S. mirim inhabited the organic soil layer (0-3.5 cm depth) where monthly catches of juveniles were negatively correlated with temperatures of the soil. Females were twice as abundant as males. The lack of a distinct reproductive period and the presence of juveniles (in particular the first nymphal instar) and adults (both sexes) throughout the year indicate a plurivoltine mode of life. Few specimens were caught on the soil surface, none on tree trunks and in the canopy. Abundance of S. mirim is compared with that of the Palpigradi (microwhip scorpions) and Uropygi/Thelyphonida (vinegaroons) from the same study site. Schizomids obtained from the soil of four other upland forests in Central Amazonia (0-14 cm depth) accounted for ≤0.1% of the total arthropod fauna and represented three additional species.
Sharing a web: a phylogenetic view of sociality and kleptoparasitism in cobweb spiders (Araneae, Theridiidae)
Theridiidae is one of the largest spider families comprising over 2200 described species in 73 genera and exhibiting extreme diversity in morphology, ecology and behavior. Although spiders in general are strictly solitary, Theridiidae includes many species that share webs, either with conspecifics (sociality) or with other, often distantly related, species (commensalism/kleptoparasitism). Web sharing in either sense differs dramatically from the life strategy of most other arachnids. Although ideas abound, understanding of the evolution of these systems is still in its infancy. The construction of a detailed phylogeny is a highly advisable first step, and we here present the first cladistic analysis of the family, including 31 valid theridiid genera and 220 morphological/behavioral and about 2000 molecular characters. The results clarify generic relationships within the family, justify many genera objectively for the first time, and depict the evolution of many interesting theridiid features. While theridiids have long been known to include many social species, these results imply particularly frequent independent origins of social behavior. Features that may facilitate the evolution of sociality in spiders can be proposed. Kleptoparasitic theridiids outnumber social species, but kleptoparasitic behavior is apparently monophyletic within theridiids. Kleptoparasitism is primitive for Argyrodes and thus the simple line webs and solitary living of some species groups is secondary. The genus Argyrodes as currently delimited is monophyletic, but contains a number of both morphologically and behaviorally distinct subclades that may merit generic ranks. Names are available for these clades.
Castaways in paradise: patterns of colonization and diversification of two spider genera in the Hawaiian islands
Hot-spot archipelagoes provide exceptional models for the study of the evolutionary process, due to the effects of isolation and topographical diversity in inducing the formation of unique biotic assemblages. In particular, the Hawaiian Islands are the summits of a chain of volcanoes arranged linearly by age, the result of tectonic movement from a single volcanic hot spot in the middle of the northern Pacific Ocean, 3,500 km from the nearest continent. Over time, islands are eroded, with the older islands of the Hawaiian chain now reduced to small atolls. Accordingly, although similar islands have occupied the same location for 80 My, the present-day high islands span a time interval of only 5 My. Several spider groups have undergone explosive diversification in the archipelago, including the cobweb spider genus Theridion and the jumping spider genus Sandalodes. Approximately a dozen of endemic species of each of these two genera are known to occur across the major islands. Here, we address issues related to the origin, colonization, speciation and biogeographic patterns exhibited by the genera Theridion and Sandalodes in the Hawaiian islands, as inferred from a cladistic analysis based on a combined data set including sequences of the mitochondrial genes CoI, 16SrRNA, tRNA-leu and NADH1 and the nuclear spacing region ITS-2. These two spider genera represent two distinct life styles found in spiders, web-building (Theridion) and non-web building ground/leaf-dwelling (Sandalodes). Preliminary data suggest that the two genera display opposite colonization patterns: to the southeast for Theridion, which is congruent with the geological ages of the islands (pattern also known as the "progression rule"), and to the northwest for Sandalodes. Speciation in allopatry appears to be the main factor involved in shaping the diversification of both groups while secondary sympatry is achieved through either character displacement or competitive exclusion. The validity of this hypothesis remains to be investigated.
Phylogeography of the desert spider, Agelenopsis aperta: assessing the importance of habitat type versus geographic location
In the past phylogeography has been primarily used to track historical events of species, such as colonization of islands or population fragmentation. A little used but potentially powerful application of phylogeography is to trace the evolutionary history of adaptations to different habitats. The desert spider, Agelenopsis aperta, presents a unique opportunity to complete just such a study. An extensive background database exists for A. aperta on the genetic basis of adaptations to different habitats: arid and riparian. Furthermore, riparian patches are widely distributed throughout the spider's range of the desert southwest making migration between patches unlikely. We present preliminary phylogeographic data based on behavior, morphology, and mitochondrial DNA that allows us to assess if adaptations arose in historically isolated populations or are the result of recent natural selection.
Traditional keys versus interactive keys, an advance or only trendy? The interactive key for the Australian spider families and subfamilies -an example
Identification of many biological species is normally accomplished with traditional dichotomous keys. The author chooses the main important characters and leads the user through the key. Normally, images are not directly connected to the characters, but more modern keys directly connect text and images. However, with an interactive key, users are able to choose any character which, they think is important and select the possible states from images immediately. With normally less than 5 steps, the user finds the correct taxon. The Australian spider fauna is the most diverse in the world, with 78 of the106 currently recognised spider families, and about 2,400 described species from over 500 genera. In contrast to normal identification keys, which have only one path to each taxon, users of the interactive key are able to identify 138 subfamilies and choose from over 150 different characters with about 600 character states, each illustrated with an image. The user chooses the characters by: 1. Going through the character set in the "best" (i.e. most powerful) order determined by the program. 2: Picking a specific character set e.g. eyes, cephalothorax. Additionally, detailed descriptions and essential distribution data of families and subfamilies supports the accurate identification. This interactive key for Australian spider families and subfamilies can be the basis for further taxonomic and systematic studies of many untreated genera and species of spiders. Also, it reveals new combinations of characters by which families previously difficult to diagnose may be recognised. Interactive keys are an easy way to store data and make them available for fast and accurate identifications.
Allozyme characterization of the lycosid Hogna species of the Galapagos Archipelago
The Galapagos archipelago is situated in the Pacific Ocean at a distance between 900 and 1100 kilometers from the Ecuadorian coast. It consists of 13 large islands and a great number of islets and rocks, all of volcanic origin. Due to geographic isolation many endemic animal (e.g. Darwin finches, giant tortoises, lava lizards, mockingbirds) and plant (e.g. Opuntia cacti, Scalesia trees) groups speciated and radiated. The main evolutive studies were always focused on the vertebrate fauna and the flora. Much fewer studies in that respect were done on invertebrates. It is only very recently that a population genetic approach occurred in two Coleoptera genera , e.g. Stomium (Tenebrionidae) and Nesaecrepidia (Chrysomelidae). This paper is dealing with a population genetic approach of the lycosid spider genus Hogna based on cellulose acetate gel electrophoresis of 9 allozymes (FUM, G6PDH, GOT, IDH, LDH, MDH, MPI, PGI and PGM). During the samplings done in the period 1982-91, all existing Hogna populations of the archipelago were localized. A morphological study of the material revealed that this sampled material consisted of 6 morphological species (based on somatic differences and small differences in the palpal structure of males). Between 1996 and 2000, 29 isolated Hogna populations (29 different localities) were sampled on 10 islands {Santa Cruz, Isabela (Volcán Sierra Negra, Volcán Cerro Azul), San Cristébal, Floreana, Rábida, Genovesa, Bartolomé, Santiago and Española} for what concerns their allozyme variation. The allozyme data enable us to estimate the inter- and intraspecific differentiation of these Hogna populations.
Range expansion of the hobo spider, Tegenaria agrestis, in the Northwestern United States
The hobo spider, Tegenaria agrestis, was introduced into the United States in Seattle, Washington during the 1930's and gradually spread through Washington, Oregon and Idaho through the next 50 years. Over the years, many cases of necrotic spider bite were incorrectly attributed to Loxosceles sp., which do not occur in Pacific Northwestern states. During the 1980's and 90's, the biology of T. agrestis has become better understood. The geographic range of this medically important spider now extends into Montana, Utah, Nevada, and probably Northern California. New collection records from 1999 and 2000 document its presence in central and southwestern Wyoming.
An unusual silken nest of Yllenus arenarius (Araneae, Salticidae) - structure, function and building process
An unusual silken nest built under sand surface was described in Yllenus arenarius - a spider inhabiting sandy dunes. In this open habitat characterized by high temperature and humidity gradients as well as lack of retreats the nest has probably the key role in survival strategy of Yllenus arenarius - a dominant amongst day-active dune-dwelling spiders. Spiders built nests few millimetres under the surface after burrowing in loose sand. Four kinds of nests, different in size, structure and function were built: 1) where eggs were laid and early instars developed, 2) where spiders moulted, 3) where they overwintered and 4) the most common, where spiders survived the night and which were sometimes built during the day. Different age groups produced different number of nests per unit of time. Juveniles in their first season of life built many more nests than subadult spiders in their second season, which in turn built more nests than adult spiders. Various functions of the silken nests, their high numbers built by juveniles and possibly a high cost of producing them (in terms of synthesising protein as well as highly complicated process of building) suggest that the structures may play an important role in surviving in the dune.
Does vegetation influence spider community structure?
The organization of spider communities in three adjacent habitats (an old field, a tussock-grass field, and a deciduous woodland) in East Tennessee was investigated over a two-year period. Multivariate analyses in which plots are arranged along two or more axes on the basis of species or environmental variables (Bray-Curtis ordination) were performed on four data-sets: spider species composition, plant species composition, plant physiognomic features and habitat architecture. The ordinations based on the plant and habitat architecture data clearly separated the three different habitats. However, there was considerable overlap of the habitats based on the scores from the spider species ordinations, indicating that spider species assemblages may be fairly consistent across habitats. The ordination scores (co-ordinates) were also used in multiple logistic regression analyses to determine the relative importance of spider species assemblages, floristic assemblages, physiognomic characteristics, and habitat attributes in structuring spider communities (i.e., species distributions, species diversity and spider densities).
Do incremental increases of the herbicide glyphosate have indirect consequences for spider communities?
We examined the indirect effect of the herbicide glyphosate on field margin spider communities. Glyphosate was applied to two replicated (n=8 per treatment) randomised field experiments over two years in 1997-1998. Spiders were sampled using a modified garden vac monthly from May-October in the following treatments: 1997 comprised 90g, 180g, and 360g glyphosate ha-1 treatments and an unsprayed control; 1998 comprised 360g, 720g and 1440g glyphosate ha-1 treatments and an unsprayed control. Previously, we found that glyphosate is not directly toxic to spiders (using Lepthyphantes tenuis as a model organism), but that there is a significant short term indirect habitat effect related to increasing dead vegetation and decreasing vegetation height. We extend this analysis to examine the indirect effect of glyphosate on the spider community using DECORANA (DCA), an indirect form of gradient analysis. Subjecting DCA derived Euclidean distances (a measure of beta diversity) to the scrutiny of a repeated measures ANOVA design, we discuss the within-season effect of incremental increases in the herbicide glyphosate on arable field margin spider communities.
Web building behavior of Steatoda triangulosa (Theridiidae)
Most theridiid spiders build 'irregular' three dimensional webs, usually consisting of a horizontal tangle web suspended below a covering object or extending from a retreat, and trapping threads with sticky bases called 'gumfoots' running from the tangle web to the lower substrate. Although theridiid web building behavior has been described before, most of our knowledge is focussed on the orb-web, which makes comparisons among different web constructions difficult. We used automated methods to observe web construction in the theridiid Steatoda triangulosa under laboratory conditions. Its building behavior is more stereotyped than one might deduce from the finished web. The web is built during several nights and is sometimes only completed after more than a week. Construction consists of three different behavioral phases: initial structure, secondary structure and gumfoots. When the spider was first introduced to the observation arena, it began - after an initial period of orientation - building a three-dimensional supporting structure, made initially of several threads radiating sideways and downwards from the retreat. This structure, which was made only once during the initial web building process, was later modified and strengthened to keep the gumfoots in tension. In the second phase, the initial-structural threads were interconnected and extended. To build gumfoots, the spider started from the retreat, moving along a structural thread, it then dropped down at regular intervals to attach the thread at the lower substrate. On returning, it coated the lowest part of the thread with viscid silk, before moving back along the same thread to the starting point. The spider then continued moving along the same structural thread to drop down again to build the next gumfoot. This behavior was continued until the spider had built a series of gumfoots. There were regular intervals between the building of two gumfoot series. Thus a single web included many gumfoot series built in different stages.
Female control of male insertions by post-mating sexual cannibalism in Latrodectus revivensis (Theridiidae)
Males and females of the sexually cannibalistic black widow spiders (genus Latrodectus) are known to be under strong selection to control fertilization. Male Latrodectus revivensis frequently lose their embolus tips inside the openings of the paired conduit-type spermathecae of the females after mating. It was shown that a male embolus tip acts as true mating plug by establishing a physical barrier for subsequent males. As males are well adapted to plug the spermathecal openings, sperm priority patterns and, hence, the outcome of multiple matings of a female can not be solely determined by the shape of the female spermathecae or sperm competition inside a single spermatheca. Mainly the ability to be the first to mate with a virgin female and plug one or even both spermathecae will determine the mating success of a given male. A counter-adaptation of the female to a possible monopolization of a single male could be to control the number of successful insertions and, thus, the number of plugged spermatheca by rejecting or even cannibalizing males. In the laboratory males were allowed to mate with virgin females. Males were then checked for the loss of their tips in two time intervals. Leg length of males and females, time of tip loss and cannibalism by the female was recorded. All males were accepted for mating and more than 90% lost at least one embolus tip. 26% of the males got cannibalized and only one of these cannibalized males lost both embolus tips. Additionally, cannibalized males were significantly smaller than non-cannibalized ones and males that had their first mating in the later time interval tend to be bigger than earlier mating ones. Male Latrodectus revivensis do not show any signs of self sacrifice or complicity, but actively resist consumption by the rapacious female. However, sexual cannibalism of males of less quality that had only one successful insertion could be a tool of the female to control paternity: she can wait for a potentially better male without facing the risk of remaining unmated.
Inbreeding avoidance and non-kin biased cannibalism: the role of kin-recognition in a pre-social spider
Web sites of the subsocial spider Stegodyphus lineatus are clustered in distribution owing to restricted dispersal of young. If both males and females are philopatric, mating may occur among close relatives. Inbreeding could be avoided by discrimination against close kin as mates through kin-recognition. Kin-recognition may serve multiple functions in the evolution of spider social behaviour. The cannibalistic behaviour commonly found in spiders may help to explain why co-operative group living is relatively rare. In the transition from subsocial to permanent social group structure increased tolerance among kin should be selected for to avoid loss of inclusive fitness by cannibalism. We investigated the occurrence of kin-recognition in S. lineatus experimentally at two life-history stages: 1) during the mating season in adult and subadult individuals and 2) during initial dispersal in juvenile spiders. 1) We performed mating trials between either full sibs or non-related pairs and analysed for behavioural differences such as levels of female aggression towards males or failure of males to perform courtship behaviour. We found no difference in female aggression towards sib and non-sib males. However, more males failed to enter female nests in sib pairs compared with non-sib pairs, and in kin trials it took males longer to enter female nests than in non-kin trials. Our results suggest that inbreeding avoidance in S. lineatus may be obtained through kin-recognition. 2) Cannibalism rates within kin and non-kin pairs or groups of six juvenile spiders were compared. In spider pairs, we found low levels of cannibalism with no difference between kin and non-kin. In groups of six spiders tested under two feeding conditions, more cannibalistic events occurred and higher numbers of spiders were cannibalised within mixed parental groups compared with family groups and in low food treatment compared with intermediate food levels. These results suggest a mechanism of distinguishing kin from non-kin in S. lineatus under certain conditions, e.g. where levels of competition are high.
The genetic structure of the venom enzyme sphingomyelinase D and the role of venom in prey capture in Loxosceles arizonica
The venoms of Loxosceles spiders contain an enzyme, sphingomyelinase D that is currently thought to be unique to this lineage. The enzyme is only known elsewhere from pathogenic bacteria. Here I will present preliminary information about the structure of the gene that codes for this enzyme in Loxosceles arizonica. I will also present results of laboratory observations of prey capture by this species with the goal of better understanding the natural effects of envenomation on prey. Using RT-PCR of RNA from venom gland extracts I have sequenced the cDNA for sphingomyelinase D. Using the cDNA sequence to probe a genomic library I am identifying the genomic sequence. The gene contains at least four introns. There is a transposable element flanking the gene. The presence of introns and lack of sequence homology with sphingomyelinase D from bacterial pathogens is evidence against the hypothesis that this enzyme originated in this spider lineage by a horizontal transfer event from bacteria. Observations of prey capture by L. arizonica indicate that venom plays a central role in immobilizing prey. Spiders cautiously approach prey then deliver a bite often to an extremity. Spiders then walk away from prey (2-3 cm) and return after the onset of paralysis. Venoms irreversibly immobilize larval Manduca sexta, ants, and crickets.
B.K. Biswas Zoological Survey of India, M-Block, New Alipore, Calcutta-700 053, India
Spider Fauna (Araneae) of India: State of Art
The paper deals with the State of the Art of spider fauna of India, with emphasis on the taxonomic diversity of the Araneae, their distribution pattern within State boundaries as well as distribution patterns within the major natural ecosystems and according to biogeographic zones. It also incorporates the occurrence and distribution of Palaearctic, Ethiopian and Australian elements of spiders in the country. In addition to this the economic importance of spiders are also stated.
The influence of food abundance and starvation on dispersal in the social spider, Stegodyphus mimosarum (Araneae: Eresidae)
Colonies of the social spider, Stegodyphus mimosarum, are philopatric and inbred, with limited dispersal capabilities. However, colony founding events by mature males and females have been observed periodically. We set out to test the influence of food on the spiders' readiness to leave a colony. Thirty colonies (40 spiders in each) were established under laboratory conditions. Half of these were fed daily on an abundance of prey items, and half were not fed at all. In fifteen colonies the mean amount of food available was therefore greater than the mean requirements of the colony, and in the other fifteen, the mean amount of food available was less than the mean amount required by the colony. This treatment continued for thirty-one days, during which time the colonies were confined in netting. Thereafter, the colonies were freed from the netting, permitting emigration. Movement from a total of thirty colonies was noted during the following two weeks. We expected more spiders to leave the famished colonies due to starvation. However, a significant absolute number of spiders left colonies where food was abundant. While fewer spiders left unfed colonies, more of these spiders died, such that the relative number of spiders remaining at the end of the trial was not significantly different between treatments. Even when they were starved, the decision to leave a colony was not based on a lack of food. Low food availability increased mortality, yet it did not alter the remaining spiders' decision to move. Therefore the decision to move is based on factors beyond prey availability and these could include the stage of development or the maturity of the spiders.
A community of mimics: ant-like jumping spiders (Araneae: Salticidae) of the Neotropics
Mimicry of ants has evolved at least fifteen times in spiders, and at least four times within the family Salticidae. One intensively surveyed lowland tropical rainforest site in Costa Rica yielded twenty species which bear morphological and behavioral resemblance to numerous types of ants; seven of these are new to science. Several more undescribed species were found from other parts of Costa Rica. Natural history is poorly known for all these species, although studies of related taxa suggests that mimicry primarily serves to protect these animals from visual predators. In the course of this study, we found hints of habitat partitioning amongst related species, particularly between canopy and understory dwellers. Matches with ant models are proposed, with varying degrees of specificity, and patterns of model-mimic evolution are discussed. A pictoral field guide and expanded range maps have been developed for these and related species in the region, in the hopes of promoting additional research on these organisms.
Deep molecular divergence in the absence of morphological and ecological change in the Californian coastal dune endemic trapdoor spider Aptostichus simus
Aptostichus simus is a trapdoor spider endemic to the coastal dunes of central and southern California and, on morphological grounds, is recognized as a single species. Mitochondrial DNA 16S rRNA sequences demonstrate that most populations are fixed for the same haplotype and that the population haplotypes from San Diego County, Los Angeles County, Santa Rosa Island, and Monterey County are extremely divergent (6 - 12%), with estimated separation times ranging from 2 to 6 million years. A statistical cluster analysis of morphological features demonstrates that this genetic divergence is not reflected in anatomical features that might signify ecological differentiation among these lineages. The species status of these divergent populations of A. simus depends upon the species concept utilized. If a time - limited genealogical perspective is employed A. simus would be separated at the base into two genetically distinct species. This study suggests that species concepts based on morphological distinctiveness, in spider groups with limited dispersal capabilities, probably underestimate true evolutionary diversity.
Spider communities in the Flemish coastal dunes: community stability and indicator species
From 1976 on, the araneofauna of the Flemish coastal dunes was investigated by means of year-round pitfall sampling. The community structure, as determined by means of ordination techniques reveals the importance of vegetation succession, hydrology and disturbance (management, sand dynamics) for the conservation of the total spider fauna. Within the framework of a recent management monitoring program, indicator species for the different habitat types are determined by using the Indicator Value methodology. The most extreme habitats (dune woodlands, non-vegetated sand dunes) are characterised by indicator species with the highest indicator-value. These habitats are thus inhabited by the most specific species within the dune ecosystem. Indicator species for the other habitats are less specific and may be absent within the typical habitat or present in other habitat types. Finally, we discuss the constancy of the species' presence (community stability) in function of the habitat stability and the habitat surface. Habitat stability does not result in stable communities. Especially for the spider fauna of thermophilious grasslands (grey dunes, rabbit-grazed pastures), patch size determines the community structure: total species numbers are not dependent of the patch surface but the number of typical species increases with the habitat size. This is the result of increased edge effects and stochastic extinction processes within the small and isolated grassland fragments.
Are liocranid polyphyletic?
The phylogeny of the spider families Liocranidae and Corinnidae has been studied at the generic level by performing a cladistic analysis on 40 species belonging to 24 liocranid and 13 corinnid genera. The genera Clubiona (Clubionidae) and Gnaphosa (Gnaphosidae) were used as outgroups. Specimens were scored for 151 morphological characters, 116 somatic and 35 genitalic. Under implied weighting, a single fittest tree was found. In this tree, seven phrurolithine genera including Phrurolithus, as well as the enigmatic genera Orthobula and Hortipes, are grouped in a large clade together with the tracheline and corinnine genera studied, including Corinna. A second large clade comprises two sister groups: a clade consisting of Agroeca and a number of related genera, as well as Scotina and Apostenus, and a clade comprising the four castianeirine genera studied. Liocranum, Mesiotelus and Hesperocranum constitute a monophyletic group which is not associated with the two large clades mentioned above. The affinities of the South African genus Rhaeboctesis remain unclear. The results of the analysis seriously question the prevailing classification of the former Clubionidae sensu lato. The preferred cladogram strongly suggests that at least Liocranidae, and probably also Corinnidae, are polyphyletic. However, before taxonomic conclusions can be drawn, further work is needed on a broader range of dionychan spider genera, including a SEM study of their spinneret morphology.
A comparison of major chemosensory organs in arachnids (God has a plan after all!)
For a group of animals once thought to be minimally responsive to natural chemical stimuli, terrestrial arachnids can claim some of the most elaborate chemosensory organs among the arthropoda. In a comparative neuroanatomical study of Scorpionida (Paruroctonus, Hadrurus, Parabuthus), Solpugida (Chanbria, Eremoperna), Uropygida (Mastigoproctus) and Amblypygida, each order was found to contain prominent areas of the subesophageal ganglion (cephalothoracic nerve mass) with cytoarchitecture comparable to the olfactory lobes of insects. These neuropil were typically glomerular in composition and, in the case of the scorpion pectinal neuropil, also topographically organized. The pectines are particularly amenable to detailed studies because of their size and accessibility. Electrophysiological and behavioral assays clearly show the pectines to be sexually-dimorphic chemosensory organs having > 106 sensory neurons in some species. The organization of sensory afferents in the pectinal teeth form layered neuropil beneath the two-dimensional field of pore-tipped peg sensilla, giving this structure the appearance of a chemotactic "retina." There is evidence from all orders that the anterior leg pairs are important appendages of chemoreception, the extreme being represented by amblypygids and uropygids (e.g., full antennalization of the anterior leg pair). Taken together, the Arachnida reveal an evolutionary trend toward specialization of chemosory appendages in arthropods, one that begins with gustation by leg-like appendages contacting the substrate and ends with olfaction by antenna directed into the air.
Sensory exploitation and the function of web decorations in orb-web spiders (Araneae: Araneidae)
Predators may utilise signals to exploit sensory biases of their prey and predators. The inclusion of conspicuous silk structures called decorations or stabilimenta in the webs of some orb-web spiders may be an example of a sensory exploitation system. The function of these structures has been controversial, partially due to a lack of experimental evidence. Recent research has focussed on two signaling functions: attracting prey and deterring predators. We tested these functions by using a combination of field manipulations and laboratory experiments. In the field, decorations influenced the foraging success of adult female St. Andrew's Cross spiders, Argiope keyserlingi. Furthermore, spiders construct more decorations in sites with low vegetation density. Laboratory choice experiments revealed that significantly more flies, Chrysomya varipes (Diptera: Calliphoridae), were attracted to decorated webs. However, contrary to predictions, decorations also attracted predatory attacks from juvenile and adult praying mantids, Archimantis latistylus (Mantodea: Mantidae). The results of this research suggest that A. keyserlingi faces a conflict between foraging success and risk of predation when including decorations in its web.
Colony variation in communal feeding behavior and habitat association/color pattern in the colonial species Parawixia bistriata (Araneidae)
Field studies completed on the communal spider, Parawixia bistriata identified questions concerning habitat effects on communal feeding and adult spider habitat association and coloration. Lab experiments were completed to provide insight into these behaviors. Using large versus small prey items, the degree to which individual spiders feed communally in colonies subjected to different prey availabilities is assessed. This work was completed on individuals at the 4th instar. Adult females present two distinct color morphs (brown and yellow opisthosomes), which make the individuals cryptic on the substrates they are found during their solitary stage prior to oviposition: leaf substrates or on the branches and trunks of trees. Results from a previous mark and reciprocal release experiment suggest that the yellow morph individuals exhibit a substrate preference, while brown morphs exhibit no preference. In this study, the change of color of individuals placed on either leaves or bark was examined under lab conditions. Adults of the two morphs as well as penultimate females were used in order to further tests whether the substrate coloration has any effect on the adult coloration.
Edge effect on abundance and biomass of two different spider guilds
Area and edge effects are important in structuring invertebrate communties in tropical forests.Edge effect per se may influence biological communitites by means of the modification of physicaland structural properties of the environment, as well as the interactions among the species comprising the community. The edge effect may have a differential impact on species or higher taxa, due to their differences on foraging and/or microhabitat. Being able to understand the way in which the edge effect affects the different trophic levels of, for example, tropical forests, is of major importance when considering the management of these natural resources. In this study, the edge effect on abundance and biomass of predators from two guilds was examined, namely "sit and wait" (thomisids, n=51) and "ambush" (salticids, n=78) spiders. The edge effect was produced by a road crossing continuous forest in Central Amazon, 80 km north from Manaus, Brazil. Four transects were sampled at 0, 15, 30, 70, 150, and 300 m from the edge of the road. At each of these distances there were five quadrats located 4 m apart that consisted of a circular area of 1,5 m in diameter within which vegetation was sampled using the beating method. The edge effect was noticeable for total abundance as well as for each guild. However, the pattern showed by each individual guild was different, presenting abundance peaks at 15 m for Thomisids and at 15 m and 70 m for salticids. In the latter case, the second peak was much more important. The biomass distribution pattern showed similar results. Both guilds presented the peaks at 15 m and 70 m resembling the abundance pattern but salticids did not show the first peak at 15 m. Total biomass showed the two peaks showed by the individual guilds. It is interesting to note that the edge affects abundance and biomass of the same guild in a similar way as seen in the distribution pattern for each of those variables. This means that not only abundance but also size of individual spiders are affected, possibly due to changes in insect prey abundance and/or size. However, the response of the different guilds is distinctive to each of them.
New records of the Mygalomorph spiders from Morocco
Apart from the spider family Theraphosidae, there is a lack of recent knowledge on the moroccan mygalomorph fauna. Our recent fieldwork in Morocco allows us to update the species list. In addition, some remarks on mygalomorph systematics are presented.
Argyrodes foraging versatility and influences on host populations
It has been relatively common to assume that a species of Argyrodes is commensalistic or kleptoparasitic without direct observations of behavioral interactions or actual measurements of effects on host fitness. Also, the foraging behavior of an Argyrodes species is often thought to be limited to primarily one strategy such as kleptoparasitism (prey stealing) or host predation. However, some species not only switch between these different foraging strategies, but also simultaneously exhibit other modes of foraging such as constructing their own webs, web-stealing, and silk-stealing. Argyrodes can in fact exist in a wide variety of relationships with hosts including foraging generalists (use a variety of foraging strategies), foraging specialists (use only one strategy such as kleptoparasitism), host generalists (use a variety of host species), and host specialists (specializing on a single host species). Knowing the precise nature of these relationships is integral to understanding the reciprocal effects that these interactions have on host and Argyrodes populations. For example, interpretations of patterns of host and Argyrodes population dynamics should be strongly influenced by whether there is purely a kleptoparasitic (competitive) interaction, purely a predator-prey interaction, or a shifting competitive-predatory relationship. I will examine the complexity of interrelated genetic, developmental and environmental factors responsible for foraging versatility in Argyrodes trigonum which, is both a foraging and host generalist. I will then attempt to interpret responses of host populations to additions and removals of A. trigonum in light of these complex and shifting relationships.
Thirty years experience of breeding a theraphosid spider from Ivory Coast: Scodra griseipes, in captivity
The species Scodra griseipes (Pocock, 1897) identified by E. Dresco is the largest of the spiders living in Lamto (Ivory Coast). A few males and females captured in 1971 have been mated. The juveniles born in captivity have been reared and the adults obtainedhave been mated and so on, until 2001. The population is always alive with females, males and juveniles. So during thirty years of breeding this theraposid spider, life-cycle, growth, energy budget, reproductive success and venom has been studied. Results obtained are presented and compared with those given in the literature.
Changes in spider assemblages in relation to landscape attributes along two grazing gradients in Northern Australia
Cattle grazing is an extensive land use across the northern Australian rangelands, yet the impacts on invertebrate biodiversity are poorly understood. In the Victoria River District of the Northern Territory, spiders were sampled using pitfall traps and sweep nets along two gradients of grazing intensity based on distance from cattle watering points. The first gradient was in savanna on calcareous red loam soils at Kidman Springs, and the second was in grassland on cracking black clays at Mount Sanford. At Kidman Springs sampling was also carried out in two different seasons. Correspondence analysis revealed that the spider assemblages differed between the two soil types, and between the late-wet and late-dry at Kidman Springs. Canonical correspondence analysis showed that spider assemblages also varied along both grazing gradients and that surface cover variables (percent of bare ground, perennial grass, litter, shrubs and trees) and certain spider taxa helped to explain the patterns. Orb weavers in the family Araneidae displayed a positive increase in abundance with decreasing grazing intensity that was consistent across soil types and two consecutive years. Jumping spiders in the family Salticidae also increased in abundance along the gradient that was associated with increasing cover of perennial grass and trees. Patch type was also important to the distribution of the zodariid Habronestes sp. with more spiders caught in traps with a local microhabitat characterised by perennial grass, than by annual grass and litter or bare ground. These results suggest that studies that accommodate heterogeneity at the patch scale will be more useful in clarifying the relationships between changes in spider assemblages and grazing impacts.
Whence sheet webs? Web construction in Thaida peculiaris Karsch (Araneae: Austrochilidae)
The family Austrochilidae sits phylogenetically close to the root of all true spiders (suborder Araneomorphae). With a few debatable exceptions the remaining spiders (suborders Liphistiomorphae and Mygalomorphae) cannot spin sophisticated prey-catching webs. Aerial web architectures, and the complex behaviors required to construct them, therefore constitute momentous ecological and behavioral adaptations within spiders. The basic web form in austrochilids is a large concave-downward sheet emanating from a funnel-shaped retreat. According to the sole report in the literature the web of Ectatosticta davidi (Hypochilidae) is similar. Hence, the Hypochilus "lampshade" web is derived by outgroup comparison. Web construction in austrochilids presumably resembles the primitive behaviors used by original araneomorph spiders to construct their novel snares. Thaida peculiaris builds using fairly simple and not especially stereotyped behaviors, both during the construction of the non-sticky scaffolding and during sticky cribellate silk spinning. Features of Thaida web construction suggest an ethological framework for the broadly comparative study of sheet webs in spiders.
Synchronous dispersal and extinction in the social spider Stegodyphus mimosarum (Araneae: Eresidae): what drives this?
Nests of social spiders in their natural habitat are clustered and colony clusters may be short-lived. Rapid growth and subsequent extinction of colonies and colony clusters are predicted for social spider populations; however, little quantitative data exist on the longevity of colonies. Furthermore, processes that influence the growth and decline of social spider populations are poorly understood. In this study we followed a population of over 550 nests of S. mimosarum from September 1994 to December 1999 and analysed the changes in relation to abiotic (temperature and rainfall) and biotic (parasitism) factors. We observed two years of apparent population stability (1994-1995), during which nest numbers remained high and constant. This was followed in 1996 by a c. 12% decrease in the numbers of active nests. At the end of 1996 there was a mass dispersal event which was followed in 1997 by a steady decline of the population with no further recovery. Thus, the decline was preceded by dispersal and nest failure, indicating that conditions in the population were unfavourable. The population-wide synchrony of these events reflects the seasonally synchronised development in S. mimosarum. Extrinsic factors related to climate did not explain the extreme events of dispersal and population decline. The potential importance of parasitism, on the one hand, and unknown intrinsic factors, on the other, should be considered as alternative explanations that remain to be tested. Such dramatic and synchronous declines have not been recorded for its congener S. dumicola and we discuss this in relation to preliminary results which show discrepancies in inter-colony variation in mtDNA for these two species.
The use of social Stegodyphus spider retreats as nest lining by the pale chanting goshawk Melierax canorus (Falconiformes, Aves): is it about preference?
The pale chanting goshawk Melierax canorus is a species within the melaraces clade that incorporates silk nests of the social spider Stegodyphus dumicola (Araneae, Eresidae) in the construction of the nest-lining of their own nests. S. dumicola is one of two social spiders whose South African distribution ranges coincides with three raptors (M. canorus, M. matabates and Micronisus gabar) that use spider retreats. The reasons why chanting and gabar goshawks use these spider retreats has been the subject of much debate. Hypotheses which attempt to explain this trait include the following: that pale chanting goshawks select silk retreats as one of many pale-colored insulating lining materials and the occurrence of Stegodyphus spiders themselves in the goshawk nests is therefore incidental; that the capture web produced by the spiders may camouflage the raptor's nest; that there is a mutualistic relationship between the spider and the bird such that the spiders feed on ectoparasites and other insects found in the raptor while the raptor experiences reduced parasite loads. None of these hypotheses are supported by empirical evidence. In the Little Karoo, Western Cape, South Africa we initiated as study to determine the abundance and distribution of Stegodyphus retreats within pale chanting goshawk territories and to investigate whether goshawks showed a preference for spider retreats above other available material. The results indicate that nest lining was scarce and goshawks selected few spider retreats in spite of their relative abundance. This, coupled to the bird's preference for sheepskin, when available, indicates that the birds were searching for soft insulating material to line the nest rather than spider retreats per se. We discuss the impact of man-induced activity on nest lining and the potential dispersal advantages for the spiders.
M. S. Cumming 19 Walmer Drive, Highlands, Harare, Zimbabwe; (cumming@icon.co.zw)
Diversity and microhabitat separation in an assemblage of jumping spiders (Araneae: Salticidae) in Zimbabwe
There are more than 5,000 salticid species worldwide. When high salticid diversity was noted in a well wooded, structurally diverse and organically managed, 0.6 ha garden in Harare, Zimbabwe, an intensive survey (more than 40 hours per month) was conducted between September, 1998 and January, 2001. Thirty-nine salticids, from 27 genera, have thus far been recorded. Twenty-seven species are sufficiently common for comprehensive biological data to have been collected. Twenty-two species have been fully identified and two new genera (Microheros and Mashonarus [in press]) described; other new species await description. The 39 garden species vary in microhabitats, prey, life histories, (hatching and mating seasons and presence of adult males) and behaviour. Habitat separation is strongly evident and is both temporal (differences in phenology) and spatial. Each of eight microhabitats houses a consistent cluster of species. The 27 common garden species are distributed as follows: on foliage, with several habitat sub-divisions (eleven species); on tree bark and branches (six); on rocks or outside walls of buildings (one); inside buildings (one); in litter (five); on sparsely covered ground (one); on termite mounds (one); and one is a running wanderer, chasing ants over ground, vegetation or walls. A few species wander occasionally, under particular circumstances. Of the twelve rarely seen species, seven are associated with large trees. This intensive local-scale study suggests that salticid diversity may prove to be higher than is generally projected. The greatest recorded diversity in Africa (69 species from Tanzania's 3,600 km2 Mkomazi Reserve) seems low by comparison. However, relationships between local and regional species richness have yet to be established. Some gardens may be more species-rich than natural habitats because they support more prey species and offer a wider range of niches into which species from within the regional pool can settle.
Ecological differences between two cryptic lycosid spiders Pardosa lugubris and P. saltans
Pardosa lugubris and P. saltans are two closely related species that are only recently recognised. The courtship display is interpreted as the most important species barrier. Because of their almost identical appearance, their very similar genital organs and the fact that they often occur in mixed populations (sympatrically), the coexistence mechanisms and the speciation of these sibling species is only poorly understood. By analysing the distribution and habitat preference of both species in Belgium, it could be shown that both species have a distinct distribution pattern and habitat optimum, although there is still some overlap. P. lugubris was found to be a more thermophyllous species occurring in pine, birch and oak forests on a sandy soil in contrast with P. saltans, which was found mainly on loamy or sandloamy soil in beech and oak forests. The genetic isolation between both species was confirmed by the results of allozyme frequencies. Furthermore, we investigated reproductive traits in four different mixed populations to assess (1) if each species has a distinct life history strategy in agreement with its microhabitat preference and (2) if both species react similar to the same environmental conditions. Our results revealed that in each population, P. lugubris produces more eggs of a smaller size than P. saltans, which could be an adaptation to its habitat optimum. Differences between populations of the same species occurring on different places are larger than differences between the species of the same locality. This indicates that both species react strikingly similar to the same set of environmental conditions.
The trigonotarbid arachnid Anthracomartus voelkelianus Karsch, 1882
Anthracomartus voelkelianus Karsch, 1882 from the Pennsylvanian (Westphalian) of Nowa Rude, Silesia, Poland was listed in a 1953 monograph by Petrunkevitch as an incertae sedis species with type material possibly in Dresden. A. voelkelianus is the type species of the genus Anthracomartus Karsch, 1882 and historically one of the first described examples of the extinct arachnid order Trigonotarbida. It is thus a pivotal species for resolving the systematics of both Anthracomartus and a number of poorly-defined, probably congeneric, anthracomartid taxa. Karsch's figured specimens have been traced to the 'Bundesanstalt für Geowissenschaften und Rohstoffe, Berlin' and correspondence between Petrunkevitch and Késtner in the archives of the Museum für Naturkunde, Berlin implies that Petrunkevitch simply overlooked this repository information. Karsch's figured fossils are redescribed here, but additional type material cited from Dresden and Wroclaw (formerly Breslau) could not be traced. One of Karsch's figured Berlin specimens is regarded here as the holotype of A. voelkelianus, but his other fossil is evidently not conspecific and is tentatively referred here to Trigonotarbus sp. (Trigonotarbidae).
An analysis of venom from scorpions of the genus Parabuthus of southern Africa with MALDI TOF mass spectrometry
Why are some ant-mimicking spiders such poor mimics?
Ant mimicry has evolved in numerous families of spiders, and while some mimics have only a rather superficial resemblance to ants, others resemble ants very precisely in both morphology and behaviour. Although some are aggressive mimics, most are Batesian. If these spiders really are protected from predators through Batesian mimicry then one might expect that, over the course of time, the 'poor' mimics would evolve into 'good' mimics. However, a recent theoretical model (the multi-model hypothesis) shows how a poor ant mimic may actually be better protected than a good mimic provided that it has a slight resemblance to several different species of ant. Evidence from Malaysia on salticid ant mimics is presented which shows that some species associate almost exclusively with one (or a few) species of ant which they resemble closely, whereas others associate with many different ants but do not have a close resemblance to any of them. This supports the multi-model hypothesis.
Studies on the biological control of the spider Thanatus albini (Audouin) (Philodromidae) on wheat aphid species Schizaphis graminum (Rondani)
Biological control of agricultural pests using true spider species has the potential to overcome problems associated with the use of chemical pesticides. In this study the life cycle of Thanatus albini (Philodromidae) was investigated when they were reared on the aphid species Schizaphis graminum (Rondani ). The length of the life cycle was 318.75 and 278.8 days at 26 éC and 70% R.H. for females and males respectively. The food consumption of females and males was 3886 and 3279 nymphs of aphid respectively. The description of the biological aspects, mating, feeding behavior and oviposition was recorded.
Revision of the North African genus Dorceus C.L.Koch, 1846 (Araneae, Eresidae)
The genus Dorceus is revised and five species from north and west Africa are recognised and distinguished in a key. All existing type specimens were studied and all species are redescribed. Scanning electron microscopy is used in examination of male palps. A distribution map of species is provided based on verified literature. The transfer of Eresus albopictus to Dorceus is rejected. The female of D. fastuosus is described for the first time. New synonymies: D. caniceps Simon, 1910 = D. fastuosus C.L.Koch, 1846; D. eburneus (Simon, 1876) = D. latifrons Simon, 1873.
The first record of Amblypygi from Egypt
Charinus ioanniticus (Kritscher, 1959) is recorded for the first time from Egypt. Two specimens were collected from Burg El-Arab near the Mediterranean coast, north of Egypt.
Zelotes in Africa
Zelotes is one of the most easily collected and speciose spider genera in Afrotropical Africa with 71 previously described species, of which there are 21 synonymies and 10 nomina dubia. There are also 46 species new to science. The distribution of Zelotes is discussed highlighting the weaknesses of the data due to unevenness of collection and intensity of collection at different localities. The greatest number of species occurs in southern Africa (48), followed by east Africa (22), central Africa (14, all new species) and west Africa (5). Southern Africa has received wide, systematic and well designed collection coverage with over 2000 specimens been collected while elsewhere in Africa receiving less attention (less than 500 specimens). Where adequate data is available the greatest number of Zelotes species occurring sympatrically is 11 and there are distinct seasonal peaks of adult activity. Z. fuligineus occurs during the winter months, Z. humilis from Aug-Oct, Z. frenchi Sept-Nov, Z. scrutatus during Oct-Dec and Z. tuckeri in April-May.
A revision of the Hersiliidae of the Afrotropical Region
The Hersiliidae are a small family of spiders with diverse life-styles ranging from wandering tree-dwellers to ground-dwellers. They have a worldwide distribution and are represented by six genera and about 85 species Three of the genera Hersilia Audouin, 1826, Hersiliola Thorell, 1870 and Tama Simon, 1882 are known from the Afrotropical Region and are represented by 33 species. The hersiliids are placed in the Eresoidea together with the Oecobiidae and Eresidae. As part of the fulfilment of a PhD degree a revisionary study of all three genera of the Afrotropical Region are planned. A cladistic analysis of all the Afrotropical species will be undertaken with genera of the Oecobiidae and Eresidae as outgroups. All available hersiliids from eight institutions were obtained for the study. Specimens are scored for 44 morphological characters of which 29 are somatic and 15 genitalic. In comparison with the Australian hersiliid fauna the Afrotropical species have simplified genitalia. Relationships with Australian and Oriental Hersiliidae will be discussed.
Phylogeny and systematic position of Opiliones: a combined analysis of chelicerate relationships using morphological and molecular data
The ordinal level phylogeny of the Arachnida and the suprafamilial level phylogeny of the Opiliones were studied on the basis of a combined analysis of 254 morphological characters, the complete sequence of the 18S rRNA gene, and the D3 region of the 28S rRNA gene. Molecular data were collected for 63 terminal taxa. Morphological data were collected for 35 exemplar taxa of Opiliones, but groundplans are applied to some of the remaining chelicerate groups. Six extinct terminals are scored for morphological characters. The data were analyzed using strict parsimony for the morphological data matrix, and via direct optimization for the molecular and combined data matrices. A sensitivity analysis of 20 parameter sets was undertaken, and character congruence used as the optimality criterion to choose among competing hypotheses. The results obtained are unstable for the high-level chelicerate relationships (except for Tetrapulmonata and Pedipalpi), and the sister group of the Opiliones is not clearly established. However, the internal phylogeny of the Opiliones is robust to parameter choice, and allows discarding previous hypotheses of opilionid phylogeny such as the "Cyphopalpatores" or the monophyly of "Palpatores." The topology obtained is congruent with the previous hypothesis of "Palpatores" paraphyly as follows: (Cyphophthalmi (Eupnoi (Dyspnoi + Laniatores))). Resolution within the Eupnoi, Dyspnoi and Laniatores is also stable to the superfamily level, permitting a new classification system for the Opiliones.
Systematics and biogeography of migid trap door spiders (Araneae, Migidae)
A phylogeny for the Malagasy migids and exemplars of the world genera corroborates the monophyly of Migoidea (Actinopodidae plus Migidae) and Migidae, and suggests that the Malagasy migids form a monophyletic group, that Migas, Moggridgea, and Poecilomigas form a monophyletic group and that the South American migids form a monophyletic group. Migid intercontinental distributions fit a scenario for the breakup of Gondwanaland.
Pitfall trapping in population genetics studies: finding the right "solution"
In population genetic studies, it is imperative to obtain a representative sample of each of the investigated populations. We adapted the pitfall technique after encountering severe problems to collect sufficiently large numbers of individuals of Coelotes terrestris in the field. Although this spider species is among the most commonly caught spiders in pitfalls, collecting them by hand proved to be much more laborious than expected. We tested two types of live traps (one cup and one funnel trap), that had been successfully used to catch Carabid beetles. Both types did not yield enough captures. Therefore, we decided to test three different solutions (70 % ethanol, Acetic acid + TE buffer and 4% formaldehyde) for future use in the traps. Ethanol was found to be the best preservative, based on the amount of DNA that could be isolated after treatment and the ability to generate the same RAPD profile as a reference DNA sample preserved at -20éC. To test ethanol as a preservative in the field, we varied its concentration and used it in combination with traps with or without funnel. We conclude that it is best to use a funnel trap with 96% ethanol. We further recommend that for every new species to be sampled in this way, an explorative investigation should be carried out concerning where, when and how many traps should be placed (this reduces the expense of the method) and concerning the effects of different solutions on the DNA.
The influence of mound structure on the diversity of spiders (Araneae) inhabiting the abandoned mounds of the harvester termite Trinervitermes trinervoides Sjöstedt
Trinervitermes trinervoides termite mounds form an important part of the grassland ecosystem in the Free State, South Africa. When the queen termite dies the colony usually declines in number since no more progeny is being produced. The dome-shaped mounds are slowly degraded by weathering and the digging of termitivorous mammals such as the Aardvark, exposing the mound surface to colonisation by arachnids, insects, mammals and reptiles. The dynamics of spiders in these abandoned mounds were studied over a period of one year, from March 1999 to January 2000, with five mounds excavated on a bimonthly basis. A correlation was found between the spider abundance and the mound height, surface perforation and the season of collection. Numbers were highest in mounds with a high surface degradation, while a tendency existed for an increase in numbers with increased mound height. Web-building spiders (Pholcidae and Theridiidae) were largely limited to mounds with a cavity in the structure. The greatest diversity and abundance of spiders was found in the winter months, suggesting that the mounds are used by certain species only as an overwintering facility. A total of 771 spiders represented by 21 families and 82 species was collected from the 30 mounds during the course of the study. The most abundant families over the course of the study, in declining order, were the Gnaphosidae, Salticidae, Pholcidae and Oonopidae. These were the only families that represented more than 5% of the spider fauna. The most abundant species were Zelotes montana (Purcell, 1907) (Gnaphosidae) (11.69%), Smeringopus sambesicus Kraus, 1957 (Pholcidae) (10.51%), Heliophanus sp. (Salticidae) (9,86%) and Xyphinus sp. (Oonopidae) (9.21%).This was a significant study as it represented only the second study of spiders in grassland in the Free State, and was also the first study of spiders associated with T. trinervoides.
Kleptobiotic strategies of two Argyrodes spiders in Chiapas, Mexico
Argyrodes spiders are common in coffee and cacao plantations of the Pacific cost of Chiapas, Mexico. One of the most common kleptoparasitic species is A. globosus. This species parasitizes various host species and shows a number of different strategies of parasitism. A. globosus hosts include Araneidae (Gasteracantha cancriformis, Verrucosa arenata) and Tetragnathidae (Leucauge marianna, L. venusta and L. argyra). These host are also common in coffee plantations. More rarely, A. globosus may parasitize the webs of Nephila clavipes (Tetragnathidae), whereas in cacao plantations, A. globosus is only found in association with N. clavipes. A. globosus adopts different strategies of food access depending on the species of host. Some of these strategies appear to be risky for the kletoparasite. This plasticity in its behavior may be related to host aggression and the availability of food on the host's web. Argyrodes caudatus is other common kleptobiotic spider in coffee and cacao plantation found in association with N. clavipes and very rarely with other host species. A. caudatus shows only one type of prey-robbing strategy of apparently minimal risk. I will discuss the behavior of Argyrodes spiders and their hosts in coffee and cacao plantations with special reference to the different kleptoparasitic strategies of A. globosus and A. caudatus.
Long-distance movements by males of the dancing white lady spider (Leucorchestris arenicola, Sparassidae) across Namib dunes
In search for mating opportunities, adult males of the dancing white lady spider (Leucorchestris arenicola, Sparassidae) occurring in the dunes of the Namib Desert, Namibia, frequently wander far out of their 3-m-radius territories on dark nights. They move across bare dune slopes and subsequently return to their burrows. In 25 observed complete excursions, male spiders walked 44 éSD 26 m (range 6-91 m) from their burrow, and covered a path of 128é86 m (29-314 m). The return path was half as long as the outgoing path, had less than one-eighth as many turns, only rarely retraced the outgoing path (5% of distance), and seldom appeared to be aligned to landscape features. Typically, the return path had a straight section of 30é23 m (5-89 m), which was directed <2o towards the home burrow. In this way, the male approached his burrow to within 0.9é1.4 m and then turned towards it. On excursions, males crossed 1.3é1.2 (0-5) territories of adult females, and mated in about half of the excursions. Other adult males were also frequently encountered (1.7é1.5 times per excursion), but males avoided direct encounters evidently by signalling each other with intense sand drumming. Adult males differ in size and there are indications that they compete with each other for mates by long-distance movements, drum-signalling each other during excursions, interfering with mating, as well as sperm competition. These observation prompt questions concerning male orientation and its neurophysiological basis, spatial relationships, as well as the inter- and intrasexual relationships of L. arenicola.
The genetic basis of a between environment trade-off in life history traits due to heavy metal adaptation in a wolf spider
When populations are sufficiently long exposed to contaminants which reduce fitness related characteristics such as growth or mortality, tolerance mechanisms may evolve in such a way that the population is adapted to the specific environment where it lives. The advantage of being adapted is often associated with a cost, which results in different norms of reaction between the different populations when exposed to the different environments. Former research of field populations of the lycosid spider Pirata piraticus that live along the borders of the highly contaminated river Schelde, revealed that large amounts of heavy metals are present in the spiders compared to reference populations. Therefore, we tested the hypothesis if this amount of contamination resulted in an increased, genetically based tolerance towards heavy metals. We compared differences in growth between siblings exposed to contaminated and uncontaminated fruit flies of a reference and a contaminated population. The results revealed that for the uncontaminated population, a significant reduction in growth rate was observed in the exposed spiders compared to their unexposed sibs. This pattern could not be observed in the offspring from the contaminated population, which indicates an increased cadmium tolerance in the contaminated population.
Introducing spiders to children
Members of the general public are often afraid of spiders. Such fears can restrict individuals' activities, including many outdoor recreation and employment pursuits, and may hamper arachnologists' conservation initiatives. It is my contention that fear of spiders is a learned behaviour and can be reduced by informing young children about these animals. Over several years, I have developed a procedure, based on methods used by psychologists to lessen phobias, that increases children's fascination and reduces their apprehension about spiders. I recommend starting with realistic models (plastic toys), proceeding with drawings and photographs (books or projected images), small dead and live spiders (in secure containers), exuviae, and climaxing with large, live tarantulas (in small plastic cages). Depending upon the age group, this only takes 20-50 minutes. If time permits, I have such children collect live spiders from their schoolyard and then release them. Clear, non-childproof pill vials are ideal. For a "take home message" I give children plastic spider rings or line drawings for them to color. I encourage all arachnologists to do outreach activities in their local schools and children's organizations.
A newly discovered radiation of Giant Hawaiian Spiders: cladistic patterns based on morphological and molecular data
The Hawaiian spiders currently placed in the linyphiid genus Labulla represent an undescribed radiation and a genuine case of insular gigantism. Hawaiian &Labulla" have remained unstudied since the superficial description of two species at the turn of the century, thus the majority of these species remain undescribed. All the members of this radiation (thirteen species are known so far) are single island endemics. Cladistic analysis of morphological and molecular data support the monophyly of Hawaiian "Labulla" and suggests that the members of this radiation are the result of a single colonization event of the Hawaiian archipelago. This clade is not closely related to the type species of Labulla; a new linyphiid genus is required to place these Hawaiian endemics.
A preliminary study of ground spider diversity in an uplifted coral reef forest in Taiwan
We investigated the diversity of ground spiders at an uplifted coral reef forest in Kenting, southern Taiwan. The community structures of Araneae fauna between different habitats subjected to various degree of disturbance were compared. Pitfall traps were established at the following five types of habitats: primary forest, primary forest with recreation area, secondary forest, grassland with grazing operation and grassland. In each habitat, ten traps each consisting of four collecting cups were established and sampling was conducted once a month for a year (February 2000~January 2001). A total of 3172 individuals were obtains from first six months of sampling. Preliminary analysis indicated that the most abundant taxa was Lycosidae; then followed by Sparassidae and Clubionidae. Adult Linyphiidae were the most abundant on February, March and April, suggesting that this taxon reproduced mainly in Spring in southern Taiwan. The wet season and typhoons in July and August considerably impacted on ground spider communities by greatly reducing the abundance and species richness. A comparison of community structure and abundance of ground spiders between different habitats will reveal the impact of recreation operations on the biodiversity of Kenting uplifted coral reef forest.
Female genitalic dimorphism in a pholcid spider
Discontinuous individual variation among members of the same sex, in the same life stage, within a population, is an important phenomenon for our understanding of more fundamental issues in evolutionary biology. One set of morphological characters is conspicuously rare in the literature on intrasexual polymorphisms: genitalia. In our lecture we report the first case of a female genitalic polymorphism, not only the first for spiders but apparently for animals in general. We argue that the overwhelming use of genitalia in species identification practiced by many invertebrate taxonomists presents a strong bias against discovering polymorphisms in genitalia. Further methodological and practical aspects of invertebrate taxonomy are discussed that taken together make the discovery of genitalic polymorphisms very unlikely, no matter whether the phenomenon is rare or not.
Subfamily 1 of alpha-k+ channel toxins from scorpion venom enlarged
In a functional screening of the venom of the scorpion Parabuthus transvaalicus, a novel peptide toxin, active on voltage-dependent potassium channels has been discovered. The peptide was purified by a combination of gel filtration and reversed-phase chromatography and has been named 'parabutoxin 3' (PBTx3), the 10th member of subfamily 1 of the @-KTx family (called '@-KTx 1.10'). MALDI-TOF mass spectrometry indicated a mass of 4274 Da. Based on the complete primary structure of PBTx3, an amino acid sequence homology of 38 % with charybdotoxin (ChTx = @-KTx 1.1) was shown. A three-dimensional structure of PBTx3 was proposed by homology modeling and it demonstrates a typical scaffold, consisting of a single @-helix and a double stranded anti-parallel @-sheet. Verification of our findings was achieved by the recombinant synthesis of PBTx3 as part of a fusion protein. Cleavage of the protein by factor Xa resulted in the release of the recombinant peptide (rPBTx3). Yields of about 1 mg/L were obtained. With respect to the HPLC retention time, the mass spectrometry analysis and the functional properties, rPBTx3 showed to be identical to the native toxin. rPBTx3 reversibly blocks Kv1-type currents (Kv1.1, Kv1.2, Kv1.3) expressed in Xenopus laevis oocytes with different affinities: 79 uM, 514 nM and 453 nM, respectively. No effect was observed on hERG channels, Kir-type channels, 2-pore background channels (TBAK), (plant) KAT channels, hH1 Na channels and P2X channels.
Provisional phylogeny of species groups within the Xysticus C.L. Koch sensu stricto clade (Araneae: Thomisidae)
Results of my PhD research project (Revision of middle European species of the crab spider genus Xysticus C.L. Koch, 1835) suggest that Xysticus, in the traditional sense, lacks clear apomorphies and may therefore represent a paraphyletic group. However it is possible to recognise at least three monophyletic taxa within the genus (Jantscher in prep). One of these proposed taxa is a Xysticus sensu stricto clade, which comprises most of the middle European species. A provisional phylogeny for this clade is proposed here, using characters derived from male genital morphology. Current data is insufficient for a full cladistic analysis, but genital characters imply a phylogeny of the form (ulmi-group (poorly resolved clade + cristatus-group)) plus a monospecific luctator-group. The position of the latter cannot be satisfactorily resolved on current evidence due to its extraordinary pedipalp structure and it shares only synplesiomorphies with the other taxa. The ulmi-group (X. tortuosus, desidiosus, ulmi, ibex and lanio) is principally diagnosed on a hook-shaped median tegular apophysis in combination with a tooth-like lateral tegular apophysis. The cristatus-group (ferrugineus (cristatus (macedonicus + audax))) is characterised by a shovel-like lateral tegular apophysis, which becomes more developed in the clade. In X. ferrugineus this shovel is only indicated in form of a thin membrane. The poorly resolved clade, based on a horn-shaped lateral tegular apophysis, consists of several species, such as X. kochi, X. cor, X. viduus, X. bifasciatus, X. gallicus, X. erraticus, X. obscurus or X. nubilus. The relationships between them cannot be easily resolved. However, these spiders form the sister group of the cristatus-group based on the hammer-shaped median tegular apophysis. Future studies including non-european Xysticus species should allow a more comprehensive picture of phylogenetic relationships.
Causes and consequences of delayed dispersal in the cooperative spider, Anelosimus studiosus
In Anelosimus studiosus, most juveniles remain to maturity in their natal web forming temporary colonies in which individuals cooperate in web maintenance and prey capture. As there is natural variation in age at dispersal, we completed a series of experiments designed to quantify the relative costs and benefits of delayed dispersal from the perspective of both juveniles and mothers. These included both lab and field comparisons of the rates of prey capture and juvenile development for individuals in colonies and those isolated at mid-development. On average, juveniles remaining in colonies survived longer, developed faster, and had more resources per individual than did the experimentally removed 'solitary' juveniles. Further, mothers in the control group survived longer and produced second broods earlier than mothers in the experimental removal group. Overall, delayed juvenile dispersal benefits both juveniles and mothers.
Effect of light and temperature on the winter development and population synchrony of an agrobiont and a non-agrobiont wolf spider (Pardosa spp., Lycosidae, Araneae)
As a general rule, Pardosa spp. do not overwinter in adult stage in the Holarctic region. We tested on two species (P. hortensis and P. agrestis), how artificially increased temperature and/or lengthened light regime affects winter development. Juveniles and subadults of both species were collected in October from the field, and randomly assigned to either of the four treatments arising from two levels of temperature treatment (26/18éC day/night temperature regime, and outside ambient temperatures), and two levels of light regime (l:d 16:8, 8:16). The two species have different phenological pattern. P. hortensis has one reproductive period in the spring (April-May), the new generation develops in a synchronised way and overwinters uniformly in subadult stage. P. agrestis has two reproductive periods a year (in May-June and in August), thus the overwintering population is much less synchronised. The two treatment groups, which were hold at ambient temperature, did not moult after October until the end of the experiment (5 of March), irrespective of light regime and of species. However, in warm condition most of the spiders of both species reached adulthood. Intermoulting periods were significantly shorter at long daylight than at short daylight. The average time needed to reach adulthood in P. hortensis was 35 days at long, 63 days at short daylight, and for P. agrestis it was 45 and 73 days, respectively. In P. hortensis 90 % of the spiders were subadult in October, the rest needed only one more moult to reach adulthood. The population of P. agrestis was much more heterogeneous: spiders needed 1 to 4 moults to adulthood. In P. agrestis we found a strong positive correlation between the length of the intermoulting periods and the stage number, i.e. younger stages needed a shorter period to moult. The time needed until the final moults of P. agrestis collected at subadult stage was considerably longer. This suggests, that in subadults development has already halted in October, and even our artificial summer needed a considerable time to take its effect. This was not true for younger stages, they quickly benefited from the more advantageous conditions. Such a phenomenon has a strong synchronising effect on the more heterogeneous agrobiont P. agrestis population, while it is ineffective in the more synchronised non-agrobiont P. hortensis population. We believe that this flexibility of early life history and the eventual winter synchronisation is one component of the success of P. agrestis in unpredictable agricultural habitats.
Fitness consequences of kleptoparasitism by Argyrodes flavescens in Nephila pilipes
It is generally assumed, but seldom experimentally quantified, that kleptoparasites have negative effects on developmental rate and/or reproductive fitness of their hosts. In the present study, we first test how host fitness parameters such as developmental rate and reproduction are affected by kleptoparasites using kleptoparasitic spider Argyrodes flavescens and its host spider Nephila pilipes from Singapore. The impact of kleptoparasitism by A. flavescens was ascertained by comparing developmental rate, adult size and weight, egg weight and number and hatching rate of eggs in N. pilipes that had kleptoparasites on their webs with those that did not, at three levels of kleptoparasite load (0, 2, and 4). Although no mortality was observed in any treatments, there is a significant negative relationship between kleptoparasite load and host developmental rate, body size and weight at sexually maturity: in the presence of A. flavescens, N. pilipes took a longer development time to reach maturity and were smaller and lighter at maturity than those without kleptoparasites. We also found a reduced reproduction in N. pilipes caused by kleptoparasites: the weight of egg sac, weight of egg laid and number of eggs/sac decreased as kleptoparasites increased although the presence of A. flavescens had no effect on the pre-oviposition and incubation period. Furthermore, kleptoparasitism by A. flavescens significantly reduced egg hatching rate of the host spiders. Finally the reduced reproductive fitness of the host caused by kleptoparasitism is significantly correlated to the reduced host life-history traits such as age and size at sexually maturity. Overall, kleptoparasitism appears to be costly to the host. Interestingly, some individual host spiders with high kleptoparasite load were larger, developed fast, laid heavier or more eggs than those with low kleptoparasite load, suggesting a possible evolutionary arms race between kleptoparasites and hosts. However, this hypothesis remains to be tested.
Spiders on mires in North Europe
Ground-living spiders were studied on mires, mainly Sphagnum peatbogs, using pitfall traps in Sweden, Finland and northern Norway (ca 56é- 70éN). Abundant and other typical species are presented and the spider communities compared in different vegetation zones. Geographical trends in the studied spider faunas are discussed. Marked components of the present bog spider faunas, both at species and individual level, include the families Linyphiidae (a large number of typical bog species), Lycosidae (genera Pardosa, Pirata, Alopecosa, Arctosa, and Trochosa) and Gnaphosidae (Gnaphosa, Haplodrassus, Drassyllus, and Zelotes). Typical and interesting bog species are found also in many other families, e.g. in Liocranidae, Salticidae, Theridiidae and Zoridae.
Testing the assumptions of conditional handicap theory: costs and condition dependence of a sexually selected trait
Conditional handicap theory of sexual selection predicts that sexual traits are reliable signals of male quality because they are a) condition dependent and b) costly to produce or maintain. In this study my objective was to experimentally investigate whether the drumming of male Hygrolycosa rubrofasciata wolf spiders is a condition dependent costly trait. Males court females by drumming dry leaves with their abdomen and females preferentially mate with males that are drumming at higher rates. I manipulated male phenotypic condition and drumming rate simultaneously by keeping males on three different food rations and either introducing or not introducing them to a female. Food ration treatment affected male condition as males on low food ration lost mass while males at high food ration maintained their mass at a constant level. Male drumming rate was condition dependent as the manipulation of food ration affected male drumming rate: males on low food ration had the lowest drumming rate while males on high food ration drummed at highest rate. Manipulation of drumming rate incurred significant fitness costs on males as males induced to drum at higher rates suffered higher mortality than other males. Furthermore, there was a significant female introduction by food ration by male size interaction on male survival; when introduced to females, large males manipulated to be in poor condition had poorer survival than large males manipulated to be in good condition but the difference was not as pronounced when males were not introduced to females. Despite the higher mortality in female introduction group, there was still a significant positive correlation between drumming rate and survival. My results demonstrate that sexual signalling in H. rubrofasciata is condition dependent and costly, thus supporting conditional handicap models of sexual selection.
Taxonomy and ecology of new South African Anapidae (Araneae)
No abstract submitted
Promiscuous females, castrated males, and eunuchs: phylogeny and biology of Nephilinae spiders
Simon's argiopid subfamily Nephilinae consisted of the genera Singotypa Simon, Phonognatha Simon, Deliochus Simon, Nephila Leach (including Nephilengys L. Koch), Clitaetra Simon, Herennia Thorell, and Perilla Thorell. Later, Singafrotypa Benoit was described to include the African species of Simon's Singotypa, and the latter was synonymized with Phonognatha. For the most of last century Nephilinae has been retained within Araneidae, but has been lately moved to Tetragnathidae. In the only phylogenetic treatment of the family Tetragnathidae (Hormiga, Eberhard and Coddington 1995), the core of nephiline genera were analyzed. The result suggested the clade Nephilinae including Phonognatha (Clitaetra (Nephila (Herennia + Nephilengys))) being monophyletic and sister to all other tetragnathids. Of the classical nephiline genera, no phylogenetic placement has been hypothesized for Singafrotypa, Perilla and Deliochus. The most recent catalogue of Platnick lists all these "nephiline" genera in the family Tetragnathidae. Nephiline spiders are currently the subject of a worldwide taxonomic revision and phylogenetic treatment. First results are that Singafrotypa and Perilla are not nephilines and are being transferred to Araneidae. A preliminary phylogenetic analysis suggests that Deliochus and the remaining true nephilines are monophyletic. However, the tetragnathid placement of Nephilinae is ambiguous and only weakly supported. Behavioral characters may be crucial data for reconstructing nephiline phylogeny. Nephiline species are known for their interesting and sometimes bizarre sexual behavior. Females regularly copulate with more than one mate, and males exhibit fierce male-male competition when courting or guarding females. Nephila exhibits both pre- and post-copulatory cohabitation and mate-guarding. Male castration has been recorded in several genera and involves the male breaking off distal part of his embolus and/or conductor after copulation, which then remains stuck in the female copulatory opening. Presumably, castration prevents further mating of the female with the rival males. Furthermore, in Herennia and Nephilengys males often lose the entire bulbus. Such males were called eunuchs by some authors and the phenomenon remains unexplained to date.
Phylogeny of the Cranaidae and nomenclature of its subdivisions (Opiliones, Laniatores, Gonyleptoidea)
The phylogeny of the family Cranaidae is investigated. The Gonyleptoidea sensu Kury include 3 major families Gonyleptidae (830 species), Cosmetidae (710 species) and Assamiidae (435 species). The fourth most diverse family is the Cranaidae (150 species), endemic of the Andean-Amazonian part of the neotropics. This family, recently established as such is a monophyletic group (on a weak basis of loss of interlocking coxal denticles) is currently divided in four Roewerian subfamilies which were all until recently part of the Gonyleptidae. There is synapomorphic evidence -- sexual dimorphism of the prosomal part of the dorsal scute -- that Cranaidae is the sister group of the Stygnidae. The phylogeny of the cranaids, as obtained in a preliminary numeric cladistics survey, is remarkably asymmetric. Two of the four subfamilies, namely Stygnicranainae and Heterocranainae are surely monophyletic although they represent highly specialized and poorly diverse groups. The Prostygninae are the paraphyletic sister group of the other cranaids. This name should be strictly applied only to the basalmost clade (defined by striking modifications of legs III and IV) containing only three species and the two nominal genera Prostygnus Roewer and Cutervolus Roewer, which show many primitive features conserved also in basal lineages of Cosmetidae and Stygnidae. The Cranainae is a polyphyletic group including most members of the family. The most conspicuous characters present in typical cranaids are the pair of winglets in the stylus of penis, the absence of any process of the glans, the astragalus of leg I spindle-like swollen in males, the pedipalpal femur dorsally keeled and serrate, and the femur IV long and straight with a few apical spurs. It is widely known that the supraspecific groups created by Roewer are meaningless. Given the proposed phylogenetic scheme, if every clade along the main line in the family deserves the status of subfamily, then a large number of very small subfamilies would have to be created. An alternative nomenclatural approach would be to ignore the traditional subfamilies and the treat the clades as genera.
Sexual size dimorphism in a group of sheet web spiders (Linyphiidae)
This presentation describes an unusual male-biased sexual size dimorphism for a group of sheet web spiders (Linyphiidae). A comparative study of the general sexual size dimorphism within this group is presented, showing that males generally grow to a larger size at maturity. The reasons for this discrepancy from general theory of spider size dimorphism and the implications on the discussion about the evolution of sexual size dimorphism are discussed.
Phylogenetic Revision of the Gayenna tridentata species group (Araneae, Anyphaenidae, Amaurobioidinae)
A monophyletic group of species related with Gayenna tridentata Simon, which will be assigned generic status in a generic revision (by M. Ramérez, in prep.), belong to the Amaurobioidinae, a very common group of anyphaenid spiders all over Argentina and Chile. Although the group was first recognized as monophyletic by Ramérez, only three species were included in his analysis. Here, the relationships and monophyly of the Gayenna tridentata species group are revised and most of its species are described for the first time. The cladistic analysis include all the 12 so far known species presumably belonging to the species group. Continuing and deepening the previous work on Amaurobioidinae by Ramérez, his data matrix is enlarged by adding these 9 species, 8 of them undescribed, plus about 30 new morphological characters, mostly from the copulatory organs, sternum, leg spots, abdominal pattern, and spinnerets. Several of the original characters proposed by Ramérez are reinterpreted. The outgroup then consist on all but three representatives of all the genera of the subfamily Amaurobioidinae studied by Ramérez, thus resulting in a data matrix of about a hundred species and 240 characters. This data matrix is analized with parsimony under implied weights. The Gayenna tridentata species group is monophyletic and well supported, but four species known only from females have uncertain relationships. Most of the species of the species group have the anterior lateral spinnerets slightly sclerotized and a characteristic abdomen pattern. Males of the Gayenna tridentata species group can be recognized by a distinctive retrolateral tibial apophysis on the palp, and females can be recognized by a particular arrangement of the genitalia.
The family Sicariidae in the Afrotropical Region: a preliminary report
The family Sicariidae is considered to be one of the major medically important spider families of the world. The revision of the species and the possibility of new species is therefore considered to be of great importance for medical research and it is for this reason that the present study is undertaken. The Sicariidae in the Afrotropical Region, as it stands at present, has two genera. These genera are Sicarius Walckenaer, 1847, subfamily Sicariinae, and Loxosceles Heineken and Lowe, 1835, subfamily Loxoscelinae. In the Afrotropical region the genus Sicarius has six species and the genus Loxosceles has 13 species. With this in mind, and with a study of the available literature, a report is given here of the distribution of the present species and the possibility of new species and even the possibility of a new genus.
Biography of a mygalomorph trapdoor spider (Gaius villosus Rainbow) and demographic implications of longevity: is there an oedipus factor?
A year-by-year account of the life history of a 27 year old female specimen of a trapdoor spider (Gaius villosus Rainbow) is presented. The life story of this specimen is set in the context of its cohort and the habitat of the resident spiders. The study site of North Bungulla Nature Reserve is a 104 hectare bushland reserve surrounded by farmland in the wheatbelt of southwest Westem Australia. Spiders aggregate in favourable microhabitats. Burrows in a sub-population in an area approximately 1000 square metres have been regularly censused for nearly thirty years. Males take at least seven years to mature; females at least eight years and they reproduce iteroparously. Dispersion of juveniles is ambulatory and limited and because of microhabitat fidelity (in a heterogeneous bushland) some inbreeding is seen as a natural phenomenon possibly accentuated now due to confinement of populations in remnant bushland. Longevity of females and low numbers of males entering the population relative to the number of reproductively active females in any one year aiso suggest multiple matings by males and inbreeding which could include incestuous i.e. mother/son matings. However, in spite of propensity for cluster formation of burrows, longevity of females and their repeated reproductive phases, it is unlikely that mother/son matings occur. Older females may moult less frequently and in their later years possibly cease to moult, thus enabling sperm storage in their spermathecal pouches which would offset the need to continue mating regularly. Given that a female has probably mated several times before her first (and successive) brood(s) mature and the alternate year only frequency of reproductive phases, and an assumed capitalisation on stored sperm, the chance(s) of maturation of her son-progeny coinciding with her receptivity is unlikely. Thus it is doubtful that primary incestuous (oedipal) matings occur. Finally, the implications of longevity, reproductive behaviour and generational span on the long term persistence of isolated populations of Gaius villosus is discussed in relation to recent and ongoing human induced ecological changes in the landscape.
Multiple mating in the spider Stegodyphus lineatus: sexual conflict or female choice?
Females may mate with more than one male to acquire direct material or indirect genetic benefits. Alternatively, the multiple mating can result if females lose the sexual conflict over mating. In order to understand which process mediates the evolution of multiple mating, one has to quantify the balance of the female gains and losses as a result of mating with multiple partners. The females of a semelparous desert spider Stegodyphus lineatus can mate with up to five males during the season. Males provide no care for the female and offspring, thus females are unlikely to obtain direct benefits from multiple mating. Females behave aggressively towards the additional males and the large males have an advantage in mating. We compared the reproductive success in two treatment groups: single-mated and double-mated females (mated with two different males). Double-mated females were further divided into females that accepted the second male and those that rejected the second male. Reproductive success was measured as clutch size, proportion of unhatched eggs, offspring number at hatching and dispersal, mean offspring mass and nest failure. Nest failure was significantly higher in double-mated females than in single-mated ones, while mean offspring mass was significantly higher in single-mated females. Furthermore, females that rejected the second male had higher mean offspring mass than females that mated twice. The mean offspring mass in single-mated females was a function of female body mass (a condition measure) after egglaying, while there was no effect of body size (prosoma width) of either the father or mother on mean offspring mass. Thus, we document reproductive costs to females of multiple mating, with no compensating benefits. These data suggest that multiple mating in S. lineatus is mediated by intersexual conflict, rather than by female choice. However, we will get the final answer later this season by comparing the heritability estimates of male offspring size versus maternal effects, when the spiderlings will reach the maturity.
The molecular phylogeny of Argyrodes spiders (Araneae, Theridiidae) in Japan
Spiders of the genus Argyrodes are known to be kleptoparasite foragers. Their foraging mode is various; some species steal prey from their host spider, or some kill and eat other spiders. In order to clarify the evolutionary pattern of foraging mode in the genus Argyrodes, I constructed a molecular phylogeny tree of Argyrodes spiders distributed in Japan, by analyzing their DNA sequences of cytochrome oxydase subunit I in mitochondria. In this analysis I used 6 species of Argyrodes and 2 species of relatives as an outgroup; Argyrodes kumadai, A. fur, A. bonadea, A. saganus, A. flavescens, A. xiphias, and Achaearanea tepidariorum and A. japonicum. I sequenced 500 bp of DNA for each species, and analyzed 376 bp of them. The parsimony methods revealed that the only one topology was selected for the phylogeny tree and that the genus Argyrodes was monophyletic. Both A. fur and A. saganus usually capture spiders by throwing capture threads and kill spiders including web-builders. These two species had a strong connection to each other in the phylogeny tree. Consequently, this phylogeny tree indicates that the Argyrodes spiders evolved as a prey thief and afterwards specialised their foraging mode to that of a spider killer.
Scorpions of the Chaco biogeographic province in the central area of Catamarca Province, Argentina
The scorpions of Argentina have been well studied and collected. There are 40 species known from this country represented by two families, Buthidae and Bothriuridae. However, with more intensive collecting the biodiversity of the group might be richer than originally suspected. Although most areas in Argentina have been extensively collected, areas like the Catamarca Province have been poorly explored. The Central area of the Catamarca Province represents two important biogeographic provinces, Chaco (Dry Chaco and Serrano Chaco Districts) and Yungas. The aim of this study was to make an inventory of the scorpions in the districts of Chaco in Catamarca Province, to determine their biodiversity. During this study we collected scorpions from five different areas in the Dry Chaco and four ones from the Serrano Chaco from September 2000 to January 2001. Ten pit-fall traps with preservatives were placed in each area randomly in natural and in semi-urban zones and were emptied weekly. Two species were collected in Chaco Serrano District and 6 species in Chaco Dry District. The number of specimen in Dry Chaco was higher than in the Chaco Serrano. New records of the distribution of several species are given.
Sexual isolation in wolf spiders of the genus Schizocosa: ecological and phylogenetic perspectives
Many members of the nearctic wolf spider genus Schizocosa (Lycosidae) have distinctive and conspicuous courtship that involves pheromones, acoustic/vibrational and visual signals. Members of the S. ocreata group (S. ocreata (Hentz), S. crassipes (Walckenaer), S. roverni Uetz and Dondale, S. floridana Bryant, S. stridulans Stratton, and S. uetzi Stratton) show little interspecific variation in male palpal and epigynal morphology. All of these species display recognizable differences in male secondary sexual characteristics and male courtship. Historically, two species within this group (S. ocreata and S. crassipes) have been called the "brush-legged" spiders because of the distinctive bristles on the tibia of the first legs of mature males. However, some populations of these species are able to interbreed (Miller et al. 1998), suggesting that these two species may be closely related. In addition, we have observed geographical variation in courtship behavior among populations of S. crassipes and S. nr. crassipes in the Southeastern United States. Here we report on an experiment to determine the extent of sexual isolation among selected populations from disparate portions of the Southeastern region of the United States and on the possibility of asymmetry in sexual isolation. This and previous behavioral studies suggest that the brush-legged wolf spider species S. ocreata and S. crassipes are not "good" species. We present a new phylogenetic analysis that shows that both "species" are paraphyletic, thus supporting this conclusion. We comment on the likely evolutionary patterns in these species.
Ecological and behavioral characteristics of the Japanese Argyrodes species and their evolutionary significance
Twelve species of the genus Argyrodes have been recorded in Japan. Ecological and behavioral characteristics have been studied for most of the species, particularly on foraging behavior, host preference, and general life history patterns. We found that several characters appear to have evolved jointly. For example, species whose main foraging mode has been known to steal prey left on webs tend to show silk eating behaviors as well, and their hosts are mainly orb-weavers. Most of them have a multivoltine life cycle, and their body sizes are relatively small. The significance of silk eating under seasonally changing environments has been demonstrated by a case study of A. flavescens: the amount of energy gained by silk eating occupied a significant portion in seasons with poor prey availability on host webs. We hypothesize that small body size coupled with a stable food availability on large host webs made multivoltinism possible in these species. On the other hand, A. melanosoma, formerly belonged to the genus Spheropistha, appears to be closely related to A. miyashitai by the structure of the male pulp, but their foraging modes were quite different, ie., A. melanosoma feeds exclusively on spiderlings of Theridiidae while A. miyashitai showed a variety of foraging modes in various types of webs. This suggests that foraging mode of Argyrodes does not always reflect phylogeny.
Revision of the genus Liocheles (Scorpiones, Ischnuridae)
The scorpion genus Liocheles Sundevall is known from Southeast Asia, Australia and Oceania. Its Australian and Indian representatives have already been studied in detail by Koch and Tikader and Bastawade, respectively, but the genus has never been revised in its entirety. In the course of my MSc thesis all known Liocheles species were revised on the base of external characters and of hemispermatophore morphology. The latter character was already successfully applied for a taxonomic analysis of the ischnurid genus Opistacanthus by Lourenéo. It now also has proved to be highly informative for the entire family Ischnuridae, at the species level, as well as at the genus level. Specific structures of the hemispermatophores in Liocheles allowed me to distinguish new species, to resurrect species placed in synonymy and to recognise relationships.
Parabuthus granulatus identified as an important venomous scorpion species in South Africa
In this study scorpions responsible for serious envenomings were collected in order to identify the medically important venomous species. Ninety eight (98) cases of serious envenomings dealt with by the Tygerberg Poison Information Centre were entered into the study. Where possible, scorpion specimens implicated were collected for identification. Of the 34 specimens obtained, 33 were identified as Parabuthus granulatus and one as Parabuthus transvaalicus. Most of the envenomings occurred in the summer, with a peak in January and February. More than 80% of cases took place in the evening, between sundown and midnight. 75% were stung on the foot. Although most of the patients were stung outside the home and in the veld, 25% of these occurred inside the home. Parabuthus granulatus is a large scorpion (6 to 15 cm-carapace and tail), with colours ranging from light yellowish-brown to dark brown, but most often greyish-brown. The telson is unusually small for this genus. P. granulatus is the most widespread species of Parabuthus, occurring in all the southern African countries except Swaziland and Mozambique. Available data suggest that P. granulatus is generally more abundant in ecologically disturbed areas, such as dry riverbeds and human habitation. Since disturbed areas are often associated with human habitation, this tendency makes P. granulatus a prime culprit for scorpion envenoming. This case series has identified P. granulatus as the most important venomous scorpion species in South Africa. Its importance as a highly venomous species has recently been confirmed by LD50 studies, comparing its venom to those of P. transvaalicus, P. schlechteri, P. capensis and P. mossambicensis.
The Australian ground spiders of the family Gnaphosidae
The ground spiders of the Gnaphosidae family are represented in Australia and New Zealand in 17 known and 21 new genera. Four genera, namely, Anzacia, Hemicloea, Taieria, Intruda occur in Australia as well as in New Zealand. Five genera, such as Notiodrassus, Matua, Kaitawa, Nauhea and Scotophaeus were found only in New Zealand, genus Hypodrassodes is extremely diverse in New Zealand and New Caledonia. Cosmopolitan species Urozelotes rusticus (L.Koch) is found only in Australia. Also introduced is only one representative genus Zelotes with species Z. sarawakensis (Thorell). This species is widely distributed in South-East Asia and is very common in Australia. On the other hand, cosmopolitan genus Eilica is extremely diverse in Australia and Tasmania, where it is represented by 34 native species; presently there are only 19 species known outside of Australia. The distribution and taxonomic structure of Australian gnaphosidae are discussed.
M. Paulsen P.O. Box 9783, Elsburg 1407, South Africa
Field observations on Harpactira hamiltoni (Araneae: Theraphosidae)
The theraphosid Harpactira hamiltoni, Pocock, 1902 was originally known only from the Free State Province. This is the first observations on the species from the Johannesburg area in the Gauteng Province of South Africa. Over a period of four years observations were made on burrow structure, prey diversity, lifecycle, brood care and the predators of H. hamiltoni.
M. Paulsen P.O. Box 9783, Elsburg 1407, South Africa
Comparing burrow behavior and brood care between Pterinochilus junodi and Harpactira hamiltoni (Araneae: Theraphosidae)
South Africa has a rich fauna of theraphosid spiders with 48 known species. However very little is known about their behaviour. Over a period of four years two theraphosid species Harpactira hamiltoni and Pterinochilus junodi were observed in the field and in captivity. A comparison is made between the two species in regard with brood care and the removal of prey remains, moulted skins and excavated substrate.
Spinning with the dinosaurs - spiders in Upper Cretaceous amber from New Jersey (Arthopoda: Araneae)
The oldest described fossils of the extant spider families Segestriidae, Oonopidae, Oecobiidae, Dictynidae and Linyphiidae, previously known from the Tertiary, are presented from Upper Cretaceous amber of New Jersey. The third and oldest known specimen of the fossil spider family Lagonomegopidae is also described and provides further palaeontological evidence of a common Laurasian fauna. The extant genera Segestria and Oecobius are taken back a further 55 and 69-74 my respectively in the fossil record. These fossils predict the presence of the Caponiidae, Tetrablemmidae, Orsolobidae, Dysderidae, Hersiliidae, Eresidae, Pimoidae, Scytodoidea s.l., cyatholipoids, theridioids and symphytognathoids in the Cretaceous. The fossils extend the known geological range of extant spider families through and beyond the end-Cretaceous extinction. This event which affected numerous other groups probably had little effect on the Araneae. The new fossils, considered in the context of previous work on Creaceous spider biodiversity, suggest that the earlier conclusion of an early Upper Cretaceous decline in the number of spiders, was based on datasets of insufficient size.
Urticating hairs during postembryonic development in Theraphosinae (Araneae, Theraphosidae): phylogenetic implications
Abdominal urticating hairs of Theraphosinae spiders were used in recent phylogenetic analysis of genera (Pérez-Miles 1992, 1998, 2000; Pérez-Miles et al. 1996). Type III urticating hairs can occur together with Type IV or with Type I in the same specimen. This fact questioned the homology among hair types, therefore, these authors coded types as three independent presence/absence characters. Bertani & Guadanucci (1999) found urticating hairs of intermediate morphology between Types III and IV and between Types III and I. They proposed serial homology and polarized the Type III as the plesiomophic state. These results, and the occurrence of sexual dimorphism in urticating hairs in some species (male with two types, female with only one type) encouraged me to study the occurrence of urticating hair types through the postembryonic development of five theraphosid species from Uruguay. Fifty nine juveniles of different sizes were examined. In all studied species only Types I or IV occur early during development, whereas Type III urticating hairs occurred after the other types. In G. mollicoma, P. longisternale and H. uruguayensis only Type IV was found in small individuals between 3.4-7.0 mm, 2.7-7.6 mm and 2.7-6.0 mm of carapace length, respectively. These species have both types (III + IV) in larger sizes: more than 8.1, 7.8 and 6.00 mm respectively. In A. suina and E. weijenberghi only type I was found in specimens between 1.89-13.2 mm and 3.8-9.3 mm respectively; larger specimens have also type III. In species with sexual dimorphism for urticating hairs, the results are congruent with the acquisition of another type of urticating hairs in adult males. Although ontogenetic method is controversial, the results generate doubts on previously proposed transformation series. The higher homoplasy of Type III hairs in comparison with Types I and IV and preliminary morphological evidence make me suspect that Type III could mask two different types of non-homologous hairs.
The World Spider Catalog: Internet and CD-ROM versions
The (complete, Clerck-to-date) World Spider Catalog is currently available on the Internet (at http://research.amnh.org/entomology/spiders/catalog81-87/index.html) as html text files. The CD-ROM version, to be released at the Congress, also contains the information in database formats. All fields are searchable singly or in limited combinations in a DOS relational database with a runtime version included, but it is also provided as a "vanilla" Access database, and in ASCII delimited formats.
Relationships of the gnaphosoid spider families
At present, seven families are recognized within the spider superfamily Gnaphosoidea: the Ammoxenidae, Cithaeronidae, Gallieniellidae, Trochanteriidae, Lamponidae, Prodidomidae, and Gnaphosidae. A cladistic analysis is presented that concentrates on family-level relationships within the group as a whole, and generic-level relationships within the first four families.
A framework for understanding dispersal in social and subsocial Anelosimus
It is widely believed that social spiders arose from subsocial ancestors, species in which siblings remain together for part of their life cycle, but disperse prior to mating. The transition to a fully social system would have involved supression of this dispersal phase. To understand this transition we must explore the factors that lead to dispersal in the subsocial species but allow the development of large multigenerational colonies in the social species. We studied the natal dispersal patterns of a subsocial Anelosimus species in Southeastern Arizona. In this population, spiders typically disperse from their natal nests in their penultimate and antepenultimate instars over a three-month period. By tracking the natal dispersal of marked individuals, we found that the spiders typically disperse less than 5 meters from their natal nests; males and females disperse similar distances; and spiders disperse greater distances over time. The occurrence of dispersal during preadult instars and the lack of a sex difference in dispersal distance supports a resource competition explanation for dispersal. Further support for this hypothesis comes from the observation that as the spiders grow larger, they are less likely to share prey with other individuals. Understanding how competition over prey could influence natal dispersal requires considering processes at the individual, colony, and community levels. Individuals may disperse when they experience a deficit of prey intake within their natal nest. The amount of prey available for individual consumption would be a function of the amount of prey present in the environment--the community level--and of the size of the nest and the number of spiders available for prey capture--the colony level. We present a simple framework that integrates these three levels and predicts the conditions under which short-lived single-generation vs. long-lived multigenerational colonies may evolve.
A tale with a sting: scorpion systematics in southern Africa
Burrowing scorpions of the genus Opistophthalmus C.L. Koch (Scorpiones: Scorpionidae) are a conspicuous element of the southern African terrestrial arthropod fauna, where they comprise >50% of the scorpion species. These scorpions display unusually high levels of endemism and an array of specialised ecomorphological adaptations for life on different substrata (rock, sand, etc.). The genus therefore represents a convenient model for research into the biogeography and evolution of arid-zone arthropods. The genus is also in serious need of revision. A research programme into the systematics of Opistophthalmus aims to delimit the ca 80 species and infer a cladogram, using morphological and molecular (DNA sequence) data. The cladogram is intended for use in the testing of biogeographical and adaptational hypotheses (e.g. the evolution of psammophily and the biogeography of southern African sand systems) concerning the genus. Testing the monophyly of the Scorpionidae and relationships among its component genera is a further aim of this research. This talk summarises results of this research by presenting an overview of progress in our understanding of Opistophthalmus phylogeny, the position of Opistophthalmus in the Scorpionidae, and the number of species recognised in the genus.
J. Proszynski l. Krasiñskiego 71, 05-822 Milanéwek, Poland; (proszyn@robal.miiz.waw.pl)
Towards new philosophy of taxonomic identification of Salticidae
Speed of disappearance of natural environment requires from taxonomy universal and instant availability of results throughout the World. Apart from technical means by computers and Internet, necessary is conceptual progress: how can we use new opportunities, and what for. Comprehensive taxonomic databases are within our reach. They should contain hyperlinked references, diagnostic drawings and photographic documentation to all species of the World. Should be available both on Internet and on large capacity disks. To avoid delays hampering progress of research, we should introduce habit of quick displaying preprint data in our comprehensive databases. That will help other researchers, especially beginners, and those active outside main research centers. However, preprint data must be protected legally and ethically, until published in a regular way on paper; preprint data should not exclude further publication. Global availability of references was pioneered by Pierre Bonnet (in a book of 6481 pages!), and parallel by Roewer. However, access to these "Bibles" is limited by a small number of copies, publication of similar becomes more difficult because of their size. Breakthrough by use of computer in cataloguing was done about 1986 by N. I. Platnick for all families of spiders, and, with his inspiration, for Salticidae by myself. I begun hyperlinking diagnostic drawings to the Catalogue of Salticidae in 1990's, and with help of W.P. Maddison made them available through the Internet. That become now Internet "Salticidae of the World" >http://spiders.arizona.edu/salticid/main.htm<, containing drawings of 3450 species of Salticidae, out of some 4500 species described, and some photographs.
Filistatidae, Austrochilinae, and the conflictive relationships of basal Araneomorphs
Filistatidae and Austrochilinae are spider groups that resist an easy solution for the phylogeny of basal Araneomorphae. While some derived characters (reduced number of cardiac ostia, fused palpal sclerites, cheliceral lamina) support that Filistatidae are members of the Haplogynae (in Araneoclada), other characters (sternal sigilla, lack of lateral tracheae, more than one calamistral rows) suggest a more primitive affiliation. The presence of tracheae in Austrochilinae, similar as to those found in entelegyne spiders, challenges their placement among spiders with the primitive array of four booklungs (Gradungulidae and Hickmaniinae). We recently discovered that austrochilines employ the type II combing behavior previously known only for entelegynes, differing from Hypochilus and filistatids, which use type I. Misionella mendensis, a prithine filistatid, also uses the type I behavior, followed by a unique type of attachment of the cribellate thread. Reexamination of intestine and the development of posterior respiratory system in Filistatidae further erode support for their placement in Araneoclada. When all these and previous data are analyzed cladistically, two alternative placements of Filistatidae are similarly supported, either as members of Araneoclada, as previously thought, or as as a sister group of all Araneomorphae except Hypochilidae.
Problem solving in the spider families Miturgidae and Ctenidae (Araneae) in Australia and New Zealand
The genus Uliodon L. Koch is reviewed. It now includes only Uliodon albopunctatus L. Koch, 1873 and Uliodon cervinus L. Koch, 1873, and is placed in the Zoropsidae. Through an original misreading of the type specimen locality data both species were erroneously reported from Australia. Uliodon is found to be limited to New Zealand and has previously been referred to by Forster and Homann as Miturga. The subfamily Uliodoninae Lehtinen, 1967 was founded on Zora tarantulina L. Koch, 1873 later transferred to Uliodon by Simon. The diagnostic character of the subfamily, the very long path of the embolus, is not found in Uliodon and hence without a diagnosis, the subfamily name is a nomina dubium. In any case, both Uliodon and Uliodoninae are transferred to the Zoropsidae. A new genus, Mitulodon, limited to Australia and Timor is described in the Miturgidae. It includes only one species, Zora tarantulina L. Koch, 1873 which now newly includes in its synonymy, Zora australiensis L. Koch, 1873, Zora ferrugineus L. Koch, 1873, Zora torvus L. Koch, 1873, Miturga maculata Hogg, 1900, Miturga velox Hickman, 1930, and Syspira rubicunda Hogg, 1900. In New Zealand, Zealoctenus Forster & Wilton, 1973 is transferred from the Ctenidae to the Miturgidae and is very similar to the Australian Diaprograpta Simon, 1909 and Nemoctenus Forster & Wilton, 1973 and the Australian Horioctenoides Main, 1954 are synonymised with the zorid genus Argoctenus.
An aunting model explains increased sociality with increased latitude in Anelosimus studiosus
It is generally believed that higher prey densities and reduced seasonality in the tropics are related to the evolution of sociality in spiders either directly through foraging benefits, or indirectly through the easing of intraspecific competition. Which permits the exploitation of other advantages of sociality. Anelosimus studiosus is a notable exception to this in that it exhibits a "reversed" behavioral cline with the incidence of multiple female colonies and number of adult females in a colony increasing from southern Florida to northern Florida, and on to Tennessee. We present a mathematical model which explains the presence of multiple female colonies at the northern part of this species' range. The hypothesis is based on the fact that there is an altricial period during which juvenile survivorship is dependent on the presence of the mother. If the mother in a single-female colony dies, her brood will be lost. However, if a mother in a multi-female colony dies, the surviving adult females may foster her dependent brood.
Do female spiders select heavier males for the 'good genes' they possess?
While much of our research in arachnology focuses on gaining insight into spider biology, spiders also offer excellent tools for the investigation of basic ecological and evolutionary principles. An example of the application of a spider system to test a theory is given here involving sexual selection. Females exhibiting mate choice typically base choice on the quality of the feeding territories males provide or on some other immediate benefit. However, numerous examples exist of female choice in the absence of any immediate rewards. The idea that females choose males that will offer good genes (i.e., of adaptive value to the offspring) has been proposed as underlying these cases. The good genes hypothesis was tested in the desert spider, Agelenopsis aperta in which higher body mass has significant fitness benefits to both males and females. In A. aperta females actively choose heavier males as mates. Four crosses (HI/HI, HI/LO, LO/HI & LO/LO) with respect to the body masses of females/males were completed using field collected animals. The F1 offspring of the crosses were reared in the lab with behavior, weight and size determinations made at maturity. While there were significant familial and sex effects on spider mass and size, none of these morphological measures varied significantly among the crosses. The behavior of the progeny on a continuum from fearful to aggressive, however, did reflect significant cross effects. Female A. aperta apparently select larger males for the 'good' behavioral genes they offer their offspring as higher aggressiveness leads to higher body mass and greater fitness.
Male recognition of female reproductive state, but not species, based on chemical cues
The silk of wolf spiders (Lycosidae) often serves a critical function in communication. This research concerns chemically-mediated recognition in the sympatric wolf spider ethospecies Schizocosa ocreata (Hentz) and S. rovneri (Uetz and Dondale), which are reproductively isolated by differences in male courtship communication. Previous studies have shown that males of both of these species exhibit courtship behavior with equal frequency when paired with conspecific or heterospecific females and/or their silk, raising questions about species recognition. Here, we test several hypotheses about male recognition of female chemical signals: 1) does male courtship behavior vary in response to the silk of females from different species? 2) does male courtship behavior vary in response to the silk of females of different reproductive status? Male S. ocreata show decreased courtship display with washed conspecific female silk, orb weaver (Metepeira) silk, and blank controls, compared to untreated conspecific silk, suggesting that males recognize chemicals in silk. However, male S. ocreata responded with equal frequency to conspecific and closely-related, but heterospecific, Schizocosa silk. Detailed analysis of male display behavior in response to silk of female conspecifics and silk from sibling species S. rovneri reveal no significant differences. These results suggest that species recognition by males within the S. ocreata clade and/or genus Schizocosa may not be based entirely on chemical cues. However, behavior of males does vary in response to the silk of (conspecific virgin) females of different reproductive states. Males display with greater frequency and exhibit higher rates of courtship behaviors when presented with the silk of virgin adult females vs. the silk of juvenile or mated females. Moreover, the intensity of male courtship display varies with female age post-adult molt, suggesting that females signal potential receptivity with chemical means. Results provide evidence for the importance of chemical communication in a well-studied spider model system.
A comparison of the diversity and composition of ground-active spiders in Mkomazi Game Reserve, Tanzania and Etosha National Park, Namibia.
Pitfall traps were used to census ground-active spiders in 12 different habitat types in protected savanna biomes in Tanzania and Namibia. With roughly equivalent trapping effort in the two areas, a total of 245 spider species and 40 families were trapped in Mkomazi Game Reserve and 168 species and 34 families in Etosha National Park. The family composition of the fauna of the two areas was similar, with Salticidae accounting for 19 % (Mkomazi) and 16% (Etosha) of all species and Gnaphosidae accounting for 14% (Mkomazi) and 21% (Etosha) of the total. Other families that accounted for a significant proportion of species included Lycosidae (4-6%) and Zodariidae (4-8%). Despite the intensive trapping effort, there was no indication from species accumulation curves that a complete estimate of the spider species richness had been obtained from either area. The possible reasons for the differences in spider species richness and family composition in the two areas are discussed.
Interattraction and tolerance in mixed-species groups of salticids
This study examines mixed-species groupings of six salticid species from East Africa. Spiders are commonly perceived as being highly aggressive and prone to cannibalism, and only a handful of the known spider species show pronounced social attributes. Most of the reported social spider species are from web-building families, and reports of sociality in the largest spider family, the salticids, are extremely rare. Furthermore, definitions of sociality usually include some statement regarding the single-species nature of social groups. However, in East Africa, groups of salticids have been found living together in close proximity, in large mixed-species nest complexes. The mixed-species groups of salticids examined in this study are comprised of six non web-building species from a number of genera, including Afraflacilla spp., Menemerus spp., and Myrmarachne sp. This paper will outline aspects the characteristics of these unusual groups, especially the behaviours of interattraction and tolerance that occur within and between species in these colonies. Using a specially designed apparatus in laboratory-based experiments, it has been found that intraspecific interattraction and tolerance in the group-living salticid species is significantly higher than the same behaviours shown in solitary salticid species. These group-living species also show unusually high levels of interspecific interattraction and tolerance. Instances of co-operative behaviour have also been documented. Possible explanations for mixed-species group formation in these salticids, with the accompanying high levels of interspecific interattraction and tolerance, are discussed. The dynamics of being part of a mixed-species group may play an important role in survival for these East African spiders. Comparisons with mixed-species grouping in other animals are also made. Studying such mixed-species groups as single social units, using ideas from social theory, allows a novel perspective on how we view societies. This approach may be especially relevant to some social spider species, which are characterised by open colonies and often have colony 'associates' from other species.
On the nature of agrobiont spiders
Results from a seven year long nation-wide survey of spiders in Hungarian arable and natural grassland habitats are cumulated in order to reveal the key characteristics of agrobiont species. We define agrobionts as species which reach high dominance in agroecosystems, with the level of dominance sometimes reaching extremes. For instance, a single species, Pardosa agrestis, on average accounts for more than 40% of the total spider population in Hungarian arable fields. On the other hand, agrobiont spiders are not necessarily indicators of the agricultural habitat because they might be dominant in other habitat types as well. Arable fields in Hungary have a very similar agrobiont composition without significant regional differences. Literature comparison shows, that this uniformity does not hold for larger geographical regions. Given that agrobionts are successful, while other species are not, in conquering agricultural habitats, it would be interesting to see if there are similarities among the species. There could be numerous areas where such similarities could be sought: original habitat, life history, dispersal ability, foraging strategy, competitive ability, etc. In the Hungarian dataset we looked for similar patterns of the first two characteristics. Agrobiont spiders in general were much less abundant in natural habitats but in many species preference for specific natural habitat types could be shown. These preferred natural habitats were ones that are exposed to strong abiotic influences such as periodic floodings and extreme temperatures, suggesting a preadaptation of these species to disturbed habitats. The life cycle of agrobionts also showed preadaptation to crop growing season. While many closely related non-agrobiont species had maturity and reproductive period either earlier or later than the main crop vegetation period, agrobionts uniformly reached adulthood synchronously.
Testing the influence of dispersal on gene flow and genetic relatedness at local and regional geographic scales - an example from Anelosimus studiosus (Araneae: Theridiidae)
Studies concerning the evolution of social and cooperative group-living behavior are often limited to mammals, birds, and eusocial insects. My research focuses on the use of social spiders to infer how dispersal dynamics, species movements, and social structuring, influence the population genetic structure and possible evolution of advanced sociality in spiders. Major research issues were examined by closely investigating the genetic effects of limited and localized dispersal through field experiments and techniques of molecular population genetics. This study has also provided the opportunity to assess possible cases of northward population expansion. It has been hypothesized that presocial (subsocial) spiders appear to be primarily outbred, whereas their communal (quasisocial) social relatives tend to be inbred. As a result, the transition from primitive to advanced levels of sociality would have involved the suppression of dispersal, which would include a switch in breeding systems from being primarily outbred to primarily inbred. Limited dispersal affects the genetic structure of populations and possible evolution of sociality by limiting the amount of gene flow that may occur as populations expand and interact. To test the hypothesis that individuals within A. studiosus nests exhibit limited dispersal and to infer that these limitations are implicated in the disruption of gene flow among areas, 68 isolated A. studiosus nests were tagged and observed. Nearest neighbor measurements, dispersal distances, environmental factors, and sex of dispersing spiders suggested that A. studiosus populations may in fact exhibit localized dispersal leading to the inhibition of gene flow among populations. Limited dispersal has also been hypothesized to lead to the fixation of distinct alleles within populations. To assess the degree to which populations exhibit restricted or interrupted patterns of gene flow, the mitochondrial gene ND1 was sequenced for a widespread collection of populations from across Midwestern and eastern North America. These data were then combined with local dispersal information to characterize and infer possible changes in population genetic structure, population history, and to reveal recent changes in population structure and dynamics.
A revision of the South American spider genus Aglaoctenus Tullgren, 1905 (Araneae, Lycosidae, Sosippinae)
The wolf spider genus Aglaoctenus, recently considered a senior synonym of the genus Porrimosa Roewer 1961, is revised, and of its 12 original species only two are considered valid: A. castaneus (Mello-Leitão 1942) and A. lagotis (Holmberg 1876). This genus is closely related to Sosippus Simon, but differs by characteristics of the anterior eye row and male and female genitalias. It is distributed exclusively in South America (except Chile) and is easily recognised, in the field, by its funnel-shaped web. Eight specific names are considered junior synonyms of A. lagotis: Porrimosa granadensis (Keyserling), P. freiburguensis (Keyserling); P. diversa (O.P.-Cambridge), P. obscura (Keyserling), P. glieschi (Mello-Leitão), P. callipoda (Mello-Leitão), Aglaoctenus bifasciatus Tullgren and A. harknessi (Chamberlin). This species occurs in Colombia, Venezuela, Southern Peru, Bolivia, Paraguay, Central, Southeastern and Southern Brazil, Uruguay and Argentina. A. castaneus is restricted to Ecuador, Northern Peru and Northern, Northeastern and Southeastern Brazil. Aglaoctenus guianensis Caporiacco, described based on an immature specimen from the French Guyana is considered species inquirendae and Porrimosa securifera Tullgren, described based on a female specimen from Argentina, is transferred to Orinocosa Chamberlin.
W. E. Savary 813 Haight Avenue, Alameda, CA 94501; (wsavary@yahoo.com)
The arachnid order Solifugae in Baja California, Mexico: a checklist and key, with descriptions of new genera and species
While the solpugid fauna of Baja California, Mexico, remains poorly known, recent examination of previously unstudied museum collections has revealed a number of interesting new taxa from that region. Included among these taxa are two new monotypic ammotrechine genera, one containing a peculiar new species that bears cheliceral horns, and one containing a brightly marked new species that appears to be diurnal. Both genera appear to share common ancestry with the genus Ammotrechula Roewer, which reaches its greatest diversity in Baja California. New species belonging to the eremobatid genera Eremochelis Roewer and Eremobates Banks were also found. The purpose of this paper is to describe these new taxa, to comment on their relationships, and to present a checklist and key to the solpugids of Baja California, Mexico.
The resurrection of the Symphytognathidae sensu Forster, 1959 and the value of reduction characters
The present phylogenetic analysis is focussed on the Symphytognathidae sensu lato (Forster, 1959) (Anapidae, Micropholcommatidae, Mysmenidae and Symphytognathidae sensu strictu). The data matrix comprises 81 characters scored for 12 ingroup and 2 outgroup taxa. Different analysis are performed to test the influence of reduction characters (losses, simplifications, minimising of organs) on the established relationships. The value of reduction characters is discussed. Although the Symphytognathidae s. l. are in fact mostly based on characters that might have come along with miniaturisation, the taxon is most probably monophyletic. The Anapidae as currently defined are paraphyletic but constitute together with the Micropholcommatidae a well supported monophyletic group and therefore the latter are herewith synonymised with the Anapidae. It is suggested to limit the Mysmenidae by removing four Old World genera. The Sympyhtognathidae s.str. could be confirmed in the analysis, although chelicerae that are grown together in the midline are not restricted to this family but could also be found in the Mysmenidae.
Genital morphology in Oncopodidae (Opiliones, Laniatores): evolutionary trends and relationships
The Oncopodidae, a family of SE-Asian and Himalayan distribution, previously considered to be a small and rare group with uniform genitalia, is shown to be species-rich and exceptionally divers in its penis morphology. Four different penis types can be distinguished, which have parallels in numerous other laniatorean families. The possible evolution of these penis forms and the phylogenetic relationships between the taxa are discussed. Several cases of convergence are shown.
Stabilimenta attract unwelcome predators
Conspicuous behaviour exposes animals to predation; prey-attraction thus often conflicts with antipredator behaviour. The fact that a conspicuous, ultraviolet (UV)-light reflecting silken structure in the orb web of certain spider species, known as stabilimentum, makes the web obvious to both prey and predators has been used to argue that spiders benefit from building stabilimenta by attracting prey and/or defending against visually hunting predators. Here, we provide experimental evidence that stabilimenta as visual signals attract web invading, spider-eating predators with acute vision to the webs and that the predators can learn to remember a particular type of stabilimentum, thus a high risk of predation by attracting visually hunting predators. However, spiders can reduce the risk of predation by frequently changing the form of stabilimentum accordingly.
Missing links between Argyroneta and Cybaeidae revealed by fossil spiders
The European Water spider Argyroneta aquatica (Clerck, 1757), is the only spider known to live for most of its life in fresh water. Most authors agree that this species is close to Cybaeidae Simon, 1898, but it has been placed in a monotypic family Argyronetidae by some, thus emphasizing the unique adaptations for aquatic life which set this species well apart from its terrestrial relatives. These adaptations include: tracheal spiracles close to the epigastric furrow; large tracheal trunks running forward into the prosoma, including appendages; a mat of short, fine setae forming a plastron on the opisthosoma; and long setae on the proximal podomeres of the posterior legs which assist in carrying a bubble of air under water. Here, I present data from Eocene (c. 35 Ma) fossil spiders from the Isle of Wight, UK, which show the intermediate condition of a spiracle situated mid-way between the spinnerets and the epigastric furrow (i.e. in a similar position to that in juvenile Argyroneta), large tracheal trunks running forward into the prosoma, but no plastron hairs. Other features place the fossil in Cybaeidae. Younger fossil spiders, from the Miocene (c. 15 Ma) of Germany, show a similar tracheal pattern to the Isle of Wight fossils and juvenile Argyroneta, together with a plastron and long leg setae. These fossils are therefore intermediate in these adaptations between the Isle of Wight fossils and modern Argyroneta. The fossils described here elucidate the evolution of aquatic adaptations in this group of cybaeids. Argyronetinae Menge, 1869, is delimited as a subfamily of Cybaeidae on the basis of enlarged tracheal trunks running into the prosoma and a wide tracheal spiracle situated well forward of the base of the spinnerets.
Mitochondrial DNA and AFLP polymorphisms in the subsocial spider Stegodyphus lineatus (Eresidae) and the social spider Stegodyphus dumicola
We are applying mitochondrial DNA sequence variation, and nuclear variation revealed by amplified fragment length polymorphisms (AFLPs), to study population structure and dispersal in Stegodyphus lineatus from Israel and S. dumicola from Namibia. AFLPs generate a multi-band "DNA fingerprint" for each individual. While subsocial S. lineatus were highly polymorphic. In one sample of 16 individuals, 20 of 21 bands were polymorphic (H = 0.967). The cooperative social S. dumicola showed virtually no genetic variation: in one sample of 16 individuals, 0 of 18 bands were polymorphic (H = 0). This is consistent with the results of allozyme studies that showed lower genetic variation in cooperative spider species (Lubin and Crozier 1985; Smith 1986; Roeloffs and Riechert 1988; Smith and Engel 1994; Smith and Hagen 1996) than in subsocial species (e.g, Johannesen et al. 1998). For both species, we PCR amplified and sequenced a portion of the mitochondrial ND1 gene. We found both intra-and inter-population sequence variation in the subsocial species. However, we also found high levels of sequence variation in the cooperative S. dumicola. This result was surprising and unexpected. It may reflect selection on the nuclear genome, higher mutation rates in mitochondrial than nuclear genome, or aspects of the breeding biology and female dispersal in this species. Modern laboratory techniques have made the study of genetic variation in natural populations much simpler for population biologists. For example, S. lineatus DNA can be extracted from amputated legs of adult females, from shed exoskeletons and from the carcasses of mothers after they had been fed upon by their offspring. This enables us to study intergenerational transmission of genetic markers.
An overview of Argyrodes behavioral biology
Spiders in the genus Argyrodes (Araneae: Theridiidae) are found in tropical and temperate habitats world-wide. They are known to ecologists and behaviorists for their symbiotic, kleptoparasitic and predatory relationships with other spiders. Argyrodes frequently or always live in the webs of other, usually larger spiders. They subsist by capturing small prey ignored by the host, stealing larger prey potentially used by the host, eating eggs or offspring of the host, and/or feeding along with the host on prey items. Some species show extreme host specificity, others have a remarkably broad host range. Elgar (1993) reviewed the biology of Argyrodes known at that time. I will present a review of Argyrodes behavior, emphasizing research completed after 1993. I will compare Argyrodes with other symbiotic spiders and araneophagic spiders, and discuss some potentially fruitful areas for future research.
Post-embryonic development of the ovari-uterus of Euscorpius carpathicus (L.) (Scorpiones, Chactidae)
A study of post-embryonic development of the ovari-uterus has been carried out from the pullus stage to the adult stage. Histological and ultrastructural studies were realized from direct preparations of animals. Primary and secondary sexual characters are already observed at the pullus stage (juvenile 1). Males differ from females by the structure of the pectines and the presence of genital papillae. The ovari-uterus has the same aspect from the pullus to the adult stage in so far as it is tubular. The section of the tube is about 20 micrometers and it contains a simple layer of epithelial cells. In the middle of the tube large germinal cells with a clear aspect are observed. At post-pullus stage (juvenile 2) the young ovocytes differentiate and become larger (previtellogenesis). They are poor in cellular organites and they get a zona pellucida and a peduncle. Some of them become external and remain far from each other and equidistant. The number of ovocytes increases but they do not grow larger until the adult stage. The ovari-uterus lengthens in the mesosome. Primary and secondary vitellogenesis will only occur at the adult stage.
The biogeography of the genus Iomachus (Scorpiones, Ischnuridae)
Since its description by Pocock, 1893 the Genus Iomachus, present both in India and East Africa, has been the subject of many biogeographical discussions (Pocock, 1896; Kraepelin, 1905; Kraepelin, 1913; Sreenivasa-Reddy, 1968; Mani, 1974; Lourenéo, 1985). In particular, the disruptive distribution pattern and the validity of the African species were contrivers discussed. The revision of this genus, prepared by the author, as his MSc thesis, clarified the status of the African species and the Biogeography of Iomachus. The results of this study will be presented here. To support the Eastern Gondwanaland origin of the genus, similar distribution patterns of different fauna and flora elements are illustrated. These include bryophytes, higher plants, different arachnids (Araneae, Acari) and insects. In contrast to Iomachus most of these elements occur either in Madagascar and/or Sri Lanka. The absence of Iomachus on these Islands is discussed.
V. Todd Davies Queensland Museum, PO Box 3300, South Brisbane, Australia, 4069; (g.davies@uq.net.au)
A new spider genus from Tasmania, Australia (Araneae, Amphinectidae, Tasmarubriinae)
Three species of a new spider genus from Tasmania are described.
Orb-weaver niches in a Danish Calluna heath
Based on field samples, the life cycles of the four most abundant orb-weaver species (Mangora acalypha, Agalenatea redii, Neoscona adianta, and Araneus quadratus) were described. The phenology of life cycle phases related to the body sizes of the species (and thus to their prey sizes) so that only little overlap in resource use occurred during the season. Microhabitats were characterised by hub height and bridge-thread length. All species selected low web sites in dense vegetation early in their life, moving upwards and into more open vegetation as they increased in size. Size segregation thus also leads to microhabitat segregation. A separate study tested the hypothesis that the species selected the web sites with the highest availability of prey of the preferred size. Small window traps were used to record prey availability at three heights, and actual prey was collected from webs. Use of Chesson's preference index indicated the preferred prey size, and the window trap catches were then used to predict the optimal web height. Two species selected the predicted microhabitat: M. acalypha at the low position, and A. quadratus at the high position. For A. redii, no clear predictions could be made; they selected web sites of intermediate height.
New Species of Banksula with a review of the genus (Opiliones: Laniatores: Phalangodidae)
Two new species of Banksula are described. The first enlarges the concept of the genus and is assigned to a new species group which may be the sister group to the other Banksula. It is unique in numerous morphological features, is the largest species in the genus, the first non-cavernicolous species, and unlike the other species of the genus which are distributed in the Sierra Nevada foothills, occurs in the Coast Ranges of California. The second new species is a typical member of the californica group but with pronounced troglomorphy. Clinal variation is documented for B. grahami Briggs, with B. elliotti Briggs and Ubick, now placed as its junior synonym, representing its northern and most troglomorphic populations.
El Niño influence on group formation in the colonial orb-weaver Metepeira spinipes: evidence for a parasocial pathway based on risk-sensitivity?
The discovery of aggregations of the colonial web-building spider Metepeira spinipes on the Monterey peninsula in California, linked to the 1998 El Niño phenomenon, has presented a unique opportunity to examine the mechanism(s) responsible for group-living in spiders. In previous (drought) years, populations of M. spinipes in these areas were predominately solitary, but following the most recent El Niño event (1997-98), large colonies have been observed. On several trips to the central California coast (Fall 1998, Summer and Fall 1999, Summer 2000), we collected data on colonies of M. spinipes from populations at Half Moon Bay (San Mateo Co.), Asilomar State Beach and San Jose Creek State Beach (Monterey Co.). Our field studies confirm earlier observations that increases in prey insect abundance during El Niño years result in higher density of spider populations, creating conditions favorable to aggregation and social behaviour. Data indicate that spiders aggregate in greater numbers in localized sites with higher prey availability, and nearest neighbor distance decreases with increased colony size. Observations of prey availability and individual prey capture rates support the predictions of risk-sensitivity theory: i.e., spiders living in groups have reduced variance in prey. Grouping may increase fitness, as spiders living in groups have more egg sacs/female than solitaries, and variance in egg sac number decreases with colony size. Specimens collected from field populations are being used to examine the genetic structure of populations, which is currently unknown. Determination of genetic similarity among colonies and genetic relatedness among individuals within colonies using DNA sequence analysis will allow testing of hypotheses about the role of kin selection and group selection in the evolution of colonial web-building
Modelling behavioral strategies in social spiders Stegodyphus dumicola (Eresidae)
By means of individual-based modelling we described population dynamics of social spiders. With a previous model we compared scenarios of foraging behavior and found that contest competition for food describes the observed pattern of individual variability in body mass better than the scenario of scramble competition. In the current study, we test the hypothesis that pre-adult foraging success is related to adult reproductive success. We suggest that large spiders reproduce earlier and have more eggs than small ones. By further developing our initial model, we compare two strategies: (1) The timing of egg deposition as well as the number of eggs depend on the female's body mass, and (2) the date of egg deposition and the number of eggs are determined randomly. Under conditions of scarce food we found that in the first scenario the fluctuations of the number of offspring are very low which favours colony persistence. Furthermore, the probability for females to get F2-propagules is higher. In contrast, at food scarcity the random scenario leads to high variances in the number of offspring, which causes large fluctuations in colony size and tends to lead to its earlier demise.
The male dimorphism in the dwarf spider Oedothorax gibbosus (Blackwall, 1841) (Erigoninae, Linyphiidae, Araneae): how advantageous is a love hill?
Oedothorax gibbosus (Blackwall, 1841) is a rare dwarf spider species bound to oligo- and mesotrophic alder carrs. The species is characterised by the occurrence of a male dimorphism with an interdemic variation. There are two male morphs: gibbosus with a hunch and a hairy groove on its carapace and tuberosus without these features. The female puts its chelicerae in the hairy groove of the gibbosus male during courtship (Heinemann and Uhl, 2000). This behavior is further investigated with ethological and morphological methods. Also the possibility that the groove secretes pheromones is assessed. Gibbosus is probably sexually more attractive for females because of this. The copulation time on the other hand does not differ between both morphs. Both complete and incomplete copulations occur. Another advantage for the gibbosus male is the genetical dominance of the gibbosus allele. It was already shown by Maelfait et al. (1990) and Vanacker (1990) that allele G for gibbosus is dominant over allele g for tuberosus by elaborated laboratory rearings. Tuberosus tries to compensate the advantage of gibbosus. Possible compensation mechanisms are a shorter juvenile phase (application of Q10 rule), sex ratio distortion in favor of the female sex in tuberosus- genotypes and a better resistance against some environmental factors such as desiccation. Only if both male morphs would have their own advantages compensating each other to a degree dependent on the particular environment they live in, the stability of the male dimorphism, as well as its interdemic variation, in the dwarf spider Oedothorax gibbosus can be understood.
Multiple roles for pore-forming peptides in the venom of scorpions
Cationic amphipathic peptides has been found as a constituent of venom, exocrine secretions, hemolymph or interstitial fluid in a large range of organisms. Some of these substances have potent antibacterial and fungicidal properties by its pore-forming or membrane-disrupting activity. In addition they may influence eukaryotic cells by its direct effects on membrane permeability or indirectly via its effects on transmembranar signalling. Recently we found pore-forming activity in the crude venom of different species of the Parabuthus (P) genus of scorpions. We could relate this activity in the venom of P. schlechteri to a lysine-rich, cysteine-free peptide (parabutoporin, PP; 45 amino acid residus), the conformation of which was mostly a-helical. Effects of native as well as synthetic PP biological actions were investigated on superoxide production, degranulation and calcium transients in human granulocytes. The induction of ion leaks was studied in human red blood cells, rat dorsal root ganglion cells, cardiac myocytes and Xenopus oocytes. Antibacterial activity was quantified in cultures of gram-negative and gram-positive bacteria. We found that PP was able to influence cell function by interacting with membrane-associated transduction systems (G-proteins; the superoxide generating NADPH-oxidase complex). By this action PP was found to induce Ca2+ release from intracellular structures and to suppress superoxide production by granulocytes. Both effects occurred without obvious disruption of the membrane barrier. At higher concentrations pore formation, with leakage of ions and loss of intracellular compounds became evident. Analoguous effects were obtained with mastoparan, a pore-forming peptide isolated from wasp venom. Synthetic PP has potent antibacterial effects which was most prominent in gram-negative bacteria. In conclusion: PP may serve multiple functions: 1/ it may protect the exocrine venom gland from bacterial and fungal invasion and 2/ it may contribute to pain induction, directly by its pore-forming action causing depolarization and repetitive firing of sensory nociceptive nerves, and indirectly, by its effects on transmembranar transduction pathways modulating pain reception.
Making sense of Australasian lycosid generic relationships using 12s ribosomal DNA sequences
A sequence data set from the mitochondrial 12S rRNA gene subunit of 11 Australasian lycosid species (six New Zealand species and five Australian species) was generated. One of the New Zealand species is undescribed and the other ten are currently placed in Northern Hemisphere genera. Three North American lycosid species, one European species and one New Zealand pisaurid (outgroup) were also sequenced. The sequence data for the 16 species were combined with the published sequences of 12 European lycosids, two Asian lycosids and one Asian pisaurid and were phylogenetically analysed. Analysis revealed that Australasian species form clades that are distinct from European species and provides further evidence against the placement of Australasian species in Northern Hemisphere genera. There is evidence that New Zealand wolf spiders are related to a subset of Australian genera whereas the other Australian lycosid genera are related to Asian/Nearctic faunas. 12S gene sequences were found to be useful when examining relationships between closely related genera, but were not as informative for deeper generic relationships.
The influence of scale and patchiness on spider diversity in a semi-arid environment
Semi-arid scrubland in the middle east consists of a soil crust matrix overlain with patches of perennial shrubs. To understand factors influencing biodiversity in this vulnerable landscape we need to understand how this mosaic of habitats influences associated fauna. Spiders are particularly abundant in this habitat so we asked if spider diversity differed between patches and if different patch types contained either a subset of the regional species pool, or specific species guilds. We also asked whether changes in the fractal nature of the microphytic/ macrophytic mosaic altered spider diversity in this habitat. We found that the semi-arid scrubland at Sayeret Shaked (Israel) is a mosaic of spider communities which, need patches of a certain quality to develop fully. Different patch types contain communities of different species, but the community structure between patches is similar. It seems that large-scale environmental factors typical of the site as a whole influence coarse-grained community structure, while small-scale differences between patch types results in species specialisation to the different patches.
Biodiversity of spiders in a savanna ecosystem
Savanna ecosystems are very extensive in Africa, comprising about 46% of the subregion. This biome is of paramount importance to South Africa, both for the livestock and eco-tourism industry. However, despite the ecosystems' extent, only large vertebrates and plants have received formal protection while invertebrate have only been incidentally conserved in existing parks and reserves. Therefore, surveys of invertebrate fauna have become more important, especially in conserved areas where conservation strategies are already in place. Although spiders (Araneae) constitute an abundant and highly successful group of invertebrates they have not featured significantly in conservation endeavours. Prior to the 1980's very little ecological work was carried out on spiders in South Africa. The past decade has seen a great increase in the number of projects in South Africa aimed at providing an inventory of the arachnid fauna. Most current spider research is carried out under the umbrella group "South African National Survey of Arachnida" (SANSA). The current study has contributed towards the wider survey of spider fauna in South Africa. The diversity of spiders in a savanna ecosystem as well as their distribution amongst different habitat types will be dealt with.
Recent studies on populations of Brachypelma klaasi (Schmidt and Krause, 1994) (Araneae, Theraphosidae): an endangered tarantula of Mexico
Brachypelma klaasi is a rare endemic species of tarantula, existing in a few isolated populations on the Pacific coast of Mexico. Threats from habitat degradation and illegal trafficking for the pet trade have led to its inclusion in appendix II of CITES. In order to guarantee its conservation in the wild in this necessary to assess the demographic status of its populations, to investigate the effect that different harvesting regimes have on these populations, and to increase the number of individuals for the legal pet trade by breeding in captivity. Currently, harvesting is based on the capture of one particular life-cycle stage (adults) and demographic simulation will provide information on the effect that harvesting females and other stages would have on the populations. The combination of field and laboratory data will allow us to propose effective management solutions that satisfy the pet trade and preserve the populations.
Global range of rarity of spider communities of western France: an approach at different scales.
A reference base (23296 records) indicating the distribution of all the spider species of the Armorican massif (West of France) allows us to evaluate the relative rarity of each species. An index (Ip) based on the relative rarity of the spider species to estimate the conservation value of different spider communities is elaborated (Canard et al.1998). In order to explore the relative rarity at different range size, the reference base can be split into several units (administrative districts, macroclimatic areasŕ). The possibility of using different index at different scales within a biogeographic area to assess the global range of rarity of spider communities is presented.
Are the Krakatau Islands (Indonesia) a good model-area for the equilibrium theory? A Salticidae (Araneae) perspective
Since the devastating 1883-erruption the Krakatau Islands have been one of the most attractive model-areas for biogeographical research. The studies included various groups of animals (mostly arthropods) and plants in respect of the source of colonisation, the changeover rate, succession, etc. MacArthur and Wilson have tested their equilibrium theory there. Our tasks here are: (1) to answer whether the MacArthur and Wilson's model can be applied for jumping spiders; (2) to analyse the dynamics of salticid faunas for particular islands; (3) to show limitations that make biogeographical analyses of island life difficult and (4) to show how much the biological processes are unpredictable, unforeseeable and difficult to present by the mathematical models. According to many authors and despite all the limitations, there are some good reasons that make the Krakatau Islands a good model-area for the study of primary colonisation: (1) known starting point(s) of colonisation; (2) little human influence; (3) well known sources of colonisation (Sumatra and Java); (4) well documented biological history. The last two reasons seem most problematic. Typically for the tropics, both Sumatra and Java have highly diverse faunas with number of local endemics and variety of habitats. Obviously not all species are equally good candidates for colonisers having different dispersal power, habitat preferences, living in a "wrong" time and space, etc. Also the migration distance is, in fact, unknown: it would be naive to expect all the potential colonisers to depart from the southern shores of Sumatra or Java towards Krakatau Islands located 40 km away. It is known that the ballooners and/or rafters, can cover much greater distances, thus the other source-areas, either within Sumatra and Java or elsewhere have to be considered. The exchange of colonisers between the islands of Krakatau Archipelago also complicates the model because each island has different "capturing" abilities and provides different living conditions.
Zoogeography of Salticidae (Arachnida: Araneae) of New Zealand - first approach
There are about 50 species of salticids described from New Zealand, which gives the impression that the fauna is relatively well studied. However, the majority of these species were described over a 100 years ago and incorrectly classified without adequate documentation or diagnoses. Also, the type specimens are not available making the taxa impossible to verify. In January 2000 we began a long-term project on taxonomy, evolution and zoogeography of New Zealand salticids. The study is based on earlier research of Oriental, Australian and Pacific faunas, the examination of all major New Zealand collections and current field work within New Zealand. The tasks of the project are: (1) to describe (redescribe) all the taxa available from New Zealand; (2) to analyse the fauna diversity and composition for particular areas and habitats; (3) to analyse the relationships of New Zealand salticids with Australia and other areas, and (4) to reconstruct the fauna's origin and evolution. According to unpublished data (by MZ), some 30 genera and 200 species can be expected in New Zealand. The numbers are quite impressive - especially if compared with other areas of similar size and climate. The fauna is highly endemic, both on generic and specific levels and amongst endemics two groups of species/genera, "planiceps" and "auricoma", are the most diverse, Trite planiceps and "Trite" auricoma being the best known representatives of every group, respectively. The second group is made of single representatives of a few Australian genera (Opisthoncus, Holoplatys, Ocrisiona, Helpis, "Clynotis", Hypoblemum). Surprisingly, and despite the results from many other spider groups, the relationships between New Zealand and Australian faunas are very limited. The third group is made of representatives of wide-spread genera (Bianor, Neon). Finally, a few pantropical species (e. g., Hasarius adansoni) are found in the warmer climate of North Island. To some extent New Zealand is a source of fauna for other Pacific archipelagos. Representatives of (true) Trite, for instance, are found in New Caledonia and Caroline Islands. The richness and endemism of New Zealand salticids is the result of post-Gondwanan mass-extinction and speciation, the effectiveness of long-term isolation and the uniqueness of New Zealand biota and diverse climatic conditions.
Radius construction and structure in the orb-weaving spider Zilla diodia
In orb-webs, the tension of the sticky spiral produces a centripetal force on the radii, resulting in an increase in tension along each radius from the center of the web to the periphery. Zilla diodia (Araneidae) - unlike most other orb-weavers - was found to adapt the structure of its radii to this tension gradient by building radii that are doubled at the periphery of the web and single near the center. Furthermore, the proportion of each radius that is doubled was found to be larger in the upper part of the web - where the overall tension in the radii is known to be higher - than in the lower part of the web, suggesting that the spider adjusts the proportion of each radius that is doubled to the overall tension in that radius.
C.L. Craig Museum of Comparative Zoology, Harvard University, Cambridge, MA 02138; Department of Biotechnology/Biology, Tufts University, Medford, MA 02155; (ccraig@oeb.harvard.edu)
PLENARY PAPERS: ABSTRACTS
Perspectives on the evolution of complex, silk-producing systems in the Araneoidea
Studies on the evolution and ecology of web-spinning spiders suggest that silks are a key factor affecting spider diversity. Silks are highly expressed proteins that represent a substantial metabolic cost to the organisms that secrete them. The ability to produce silk has evolved repeatedly and via multiple pathways in both insects and spiders. Comparison of silk production in these two groups suggests an unusually direct link between the environment and silk gene evolution. For example, larval Lepidoptera make use of a constant and predictable resource, and all of the silk that they need is produced in one type of gland. The irregular organization of the silkworm gene suggests that selection on these proteins may be relatively relaxed. In contrast, predatory spiders that are subject to fluctuating and unpredictable resources have evolved to produce silks in a multi-gland system. Spiders with the most complex silk producing systems, the Orbiculariae, produce 4 types of silk threads and 3 types of fibrous glues that are made up of a minimum of 8 different proteins. The correlation between the evolution of the Flag gene, a 37-fold increase in species, and habitat radiation, suggests an unusually direct link between the selective environment and the evolution of the gene's molecular architecture. The highly regular exon/intron architecture of the Flag silk gene may decrease the number of errors made during translation and recombination of the gene yet result in flexibility in protein composition. This effect would allow araneoids to match silk function to the selective environments in which they are found.
What do we know about the smaller arachnid orders? - a 2001 update, with prospects and challenges
Whilst the megadiverse arachnid orders - the spiders and mites - receive considerable attention from arachnologists, the smaller arachnid orders - Pseudoscorpiones, Solifugae, Amblypygi, Schizomida, Uropygi, Palpigradi and Ricinulei - receive only modest attention. Nevertheless, as discussed during the last arachnological congress in Chicago, there have been numerous important breakthroughs in the systematics and phylogeny of some of these groups, especially during the 1990's. I here provide an update of new data on the 'minor' orders and discuss future prospects and challenges.
Genitalic polymorphism, a challenge for taxonomy
The fading of the boundaries between the different biological disciplines, taxonomy, ecology, ethology, biochemistry, in the last decennia, has greatly increased their interdependency. Genitalic polymorphism (including polymorphism of secondary sexual characters) is a typical example of a phenomenon that found no place in taxonomy as there was no framework to place it. Neither the speciation models used in ecology nor the species concept currently in use with taxonomists ôallowedô species to have discontinously polymorphic genitalia. Recent developments in ecological modelling which make sympatric speciation acceptable if modifications in at least three loci are present, and changing ideas about sexual selection, imply genitalic polymorphism in two different phases. According to the mate check hypothesis, speciation indeed goes through a phase with changes in three loci: hidden characters without shifts in somatic traits, new characters in the mating module linked to newly acquired often behavioural characters and an alteration of the recognition module which completes the process. It inevitably passes through a phase with polymorph genitalia. After the termination of the speciation process, cases of atavism with loss of behavioural adaptations through deleterious mutations or reversions, and reappearance of ancestral genital characters called "relapses", are expected to occur regularly. Without these, the "mate check" mechanism would be meaningless as it is assumed to check the presence of crucial new adaptive characters by means of the mating module. A number of examples of both types of polymorphism in arachnids are presented. It is explained why polymorphism is rarely observed although it might be a common phenomenon. As relapses cause the genitalia to return to a less complex state, quantifying complexity and similarity of genitalia is a major problem in this context. The utility of the present methods is questioned and an alternative assessing method is proposed. It is a scoring system based on the morphological distance between the original state of a structure, and its configuration after modification for its sexual function.
J. J. Ahtiainen, R. V. Alatalo, J. Mappes and L. Vertainen University of Jyvéskylé, Department of Biological and Environmental Science, PO Box 35, FIN-40351 Jyvéskylé, Finland; (jjahti@dodo.jyu.fi)
POSTER PRESENTATIONS: ABSTRACTS
Fluctuating asymmetry and sexual performance in the drumming wolf spider Hygrolycosa rubrofasciata
Recently, there has been much interest in estimating fluctuating asymmetry (FA) of morphological traits as a short-cut measure of overall individual quality. FA deals with small differences and thus measurement error is often relatively large. However, repeated measurements and large sample sizes allow reliable estimates of fluctuating asymmetry that can be corrected for errors. As an example, we estimated how much fluctuating asymmetry predicts male quality in the wolf spider Hygrolycosa rubrofasciata. Pedipalps as the most repeatable of all bilateral traits in this species were measured (n=804) with drumming activity and mobility as fitness-related references. Our data showed a very weak negative relationship between an estimate of male sexual performance and pedipalp asymmetry (r=-0.100), which inevitably underestimates the true relationship, given the measurement error. It is possible to estimate the unbiased relationship by correcting the above correlation coefficient with effective reliability estimates of FA and sexual performance, and thus r will be -0.181. In conclusion, fluctuating asymmetry as a measure of variation in male quality at the population level is suitable only if the sample size (and/or the number of repeated measurements) is large enough to overcome the masking effect of measurement error.
Fine structure of male genital system and sperm in solifugae (Arachnida)
Solifugae represent a number of peculiar characteristics that are discussed as representing a mixture of plesiomorphies and autapomorphies. Hence the position of Solifugae within the Arachnida or their relationship with other taxa is difficult to define. Nevertheless, most authors, who considered phylogenetic systematics of Arachnida, regard Solifugae as most closely related with Pseudoscorpiones. However, this putative sister-group-relationship is based on only a few characters that may be debatable. In general, phylogenetic relationships within the whole group of Arachnida are at least partly still controversial. Hence, further characters are evidently necessary to improve or falsify suggested concepts. Comparative spermatology may provide such characters. As was shown in earlier papers, spermatozoa of Eusimonia mirabilis (Karschiidae) from Marocco, the only solpugid investigated in this respect until now, are highly derived and differ strikingly from those of Pseudoscorpiones that are more close to a plesiomorphic type. Comparing sperm structure of Eusimonia mirabilis with that of sperm of all arachnid taxa, the most similar sperm cells evidently are found within the Acari-Actinotrichida. General morphology of the testis and the tendency to form aggregates of sperm are also similar in both taxa. Since sperm knowledge in Solifugae until now came only from one species in contrast to Acari in which all the higher taxa have been investigated, these characters were difficult to weighten with regard to systematical consequences. The present paper confirms the derived structure of sperm in Solifugae presenting results of two further species from Argentina including a description of male genital tract fine structure and a detailed comparison with Acari.
Proposed taxonomic and systematic work on an group of endemic New Zealand jumping spiders (Salticidae)
Knowledge of the New Zealand salticid fauna is poor in comparison to that of other families. Several species were erroneously placed in Northern Hemisphere genera and some proposed genera are polyphyletic. Members of the "Trite" auricoma pecies group are among the most common salticids in New Zealand. They are found throughout both main islands and on most offshore islands. A range of habitats are used, from forest litter and grassland to forest canopies and epiphytes. While there is several species in the group, their drab coloration and superficial similarities resulted in them being lumped into one species, "Trite" auricoma, despite being unrelated to true Trite. The "Trite" auricoma species group appears to be unrelated to any species in Australia or the Pacific islands. The monophyly of the group is supported by the morphology of adult genitalia and somatic features. The taxonomy and systematics of the group is the subject of a MSc thesis to be started this year.
From a comb to a tree: phylogenetic analysis of the comb-footed spiders (Araneae, Theridiidae) based on multiple data sets
The family Theridiidae is one of the most diverse assemblages of spiders, from both a morphological and ecological point of view. The family includes some of the very few cases of sociality reported in spiders, in addition to bizarre foraging behaviors such as kleptoparasitism and araneophagy, and radical changes in web architecture. Theridiids are one of the 7 largest families in the Araneae, with about 2200 species described. However, this species diversity is grouped in half the number of genera described for other spider families of similar species richness. Although an undeniable advance in identifying the closest relatives of the theridiids as well as establishing the family's monophyletic status has taken place in recent years through the cladistic analysis of morphological data, the comb-footed spiders remain an assemblage of poorly defined genera, among which hypothesized relationships are probably wrong or at least poorly known. Providing a cladistic structure for the Theridiidae is as essential step towards the clarification of the taxonomy of the group and the interpretation of the evolution of the diverse traits found in the family. Here we present results of a phylogenetic analysis of a thorough taxonomic sample of the family (70 taxa in 31 currently recognized genera) and representatives of 7 additional araneoid families, using multiple character data sets, including 220 phenotypic characters and about 2,000 bases, corresponding to fragments of two nuclear genes (18SrDNA and 28SrDNA) and two mitochondrial genes (16SrDNA and CoI). We examine partition support for the different clades as well as sensitivity of the results to different assumptions of the analysis will be examined.
Succession of harvestman communities in planted field hedges
The colonisation of fourplanted field hedges in an intensively managed agricultural landscape north of the Austrian Alps was studied with pitfall traps. The sites vary in age, shape, adjacent cultivation, and locality. Both hedgerows Schwand A and B were planted in autumn 1992 and studied during the first year of succession. The comparative study was continued from 1996-1998 in Schwand A, B, C (area in the shape of a triangle sparsely planted with bushes and trees in autumn 1993), and Pilgersham (the oldest hedgerow planted in autumn 1990). Its aim was not only to observe the changes in species community structure, but also to determine the differences in species communities as well as number of specimens between the centre and the edges of the plantations. Here only the data from the harvestmen are discussed. Phalangium opilio was the first harvestmen species in Schwand A and B, followed by Oligolophus tridens (C.L. Koch, 1836), Nelima semproni Szalay, 1951, Rilaena triangularis (Herbst, 1799), and Leiobunum rotundum (Latreillei, 1798). Lacinius ephippiatus (C.L. Koch, 1835), Lophopilio palpinalis (Herbst, 1799), and Paranemastoma quadripunctatum (Perty, 1833) enriched the harvestman community in Pilgersham, where only Mitopus morio (Fabricius, 1799) was decreasing in the number of specimens. Schwand C with a very low leaf-litter build-up was the poorest in species. The presentation analyses the stages of secondary succession as well as the spatial and seasonal distribution of the harvestman species. Special attention is given to the different results for females, males, and juveniles.
Risk sensitive spiders: the safety-foraging trade-off determines nest site preference in subsocial Stegodyphus lineatus
The subsocial spider Stegodyphus lineatus has a sedentary life-style and a patchy distribution due to low dispersal ability. Hence, following dispersal from maternal nest, high encounter rates with both kin and non-kin conspecifics might be expected during nest site selection. Since spiders are cannibalistic, encounters with conspecifics are dangerous. Kin-recognition would permit these spiders to avoid loss of inclusive fitness by reduced aggression towards kin. Cannibalism is more common in mixed parentage groups of S. lineatus spiderlings than in groups of sibs, suggesting that kin recognition might occur in this species. We investigated the hypotheses that S. lineatus spiderlings recognized self, kin and non-kin by nest-bound cues. Spiders were presented with the choice between two nests: 1) self versus non-sib; 2) self versus sib and 3) sib versus non-sib. To account for preferences, we considered two hypotheses: "safety" and "foraging". If safety is the determining factor for nest choice, we predict the spiders to prefer self-nests to non-self nests and sib nests to non-sib nests. Alternatively, the spider may opt for the conspecific nest as a better web site or consider it as a foraging opportunity. We found pronounced self-recognition demonstrated by a strong preference for self-nests in experiments 1 and 2, providing support for the safety hypothesis, while spiders were indifferent in preference for sib and non-sib nests. Additionally, spiderlings preferred self-nests to empty chambers, while no preference was found in non-self nest versus empty chamber trials. The trade-off between safety and foraging might change with the hunger state of the spider. This was investigated in choice experiments using starved spiders. Under low food conditions, more spiders preferred non-sib nests to self-nests, suggesting that hunger may force the spider to adopt a more risky foraging strategy. This result was supported when starved spiders selected nonsib-nests and sib-nests in empty chamber trials. Since spiders showed no preference in the sib vs. non-sib trial, we suggest that hungry spiders abandon their unsuccessful nests to search for better nest sites rather than consider the conspecific spider as prey. Thus, S. lineatus spiderlings can distinguish self from non-self nests but show no discrimination between kin and non-kin conspecifics in their hunger-dependent nest-preferences.
Catalyzing volunteer research: natural history of a tropical jumping spider fauna (Araneae: Salticidae)
Two investigators, a technical illustrator, and successive sets of novice volunteers have undertaken a "natural history inventory" of jumping spiders in Costa Rica's tropical deciduous forest. The ongoing development of a pictoral field guide to salticid species of the Santa Rosa National Park has allowed volunteers to identify the spiders they find, and has motivated them to search for new species. Low‑tech data recording protocols facilitate the accumulation of useful information on natural history, by people with a wide range of experience levels. The inventory has yielded about fifty species so far, including several new to science. Natural history observations have already established synonymy of males and females described as separate species, found that the two Lyssomanes species on site appear to sort along humidity gradients, begun an ongoing study of nesting behavior of Corythalia opima (Peckham and Peckham), and lain the groundwork for a host of other investigations. We feel that this project provides an excellent model for inventory research in that it fosters a "closed loop" of exploration; each new piece of information feeds promptly into a shared pool of knowledge and becomes accessible for further investigation by a broad set of potential researchers.
Aeronautic behavior in Erigone atra (Araneae, Erigonidae): the influence of different environmental regimes and habitability estimates
Spider dispersal may not only occur via cursorial migration but also through the air. Aeronautic dispersal 'ballooning' is still not well studied because of the difficulty to estimate effective dispersal willingness by field- or laboratory experiments. Since ballooning may result in distant migration, it is a determining factor in population exchange and as a consequence in gene flow. We conducted laboratory experiments in a test chamber, where pre-ballooning behavior could be observed. Individuals, which displayed this so-called tiptoe-behavior (i.e. stretching of the legs, followed by rising the abdomen and the production of silk threads), were considered to be ready for aeronautic behavior. Spiders of the species Erigone atra were raised under different breeding regimes. The first results indicate that the fast developing (well-fed, temperature of 20éC) individuals showed the shortest tiptoe latency time. Slower developing individuals (irregularly fed, 15éC) were characterized by a longer take-off time. Non-additive genetic variation and maternal effect or common environmental variation largely explained the observed phenotypic variation in aerial dispersal behavior. Additive genetic variation seems to be low. The observed results are discussed within an evolutionary context.
Biodiversity of Arachnida and Myriapoda of the State of São Paulo
The aim of this project is to inventory the Arachnida and Myriapoda fauna of the State of São Paulo, within the BIOTA-FAPESP program. This study will be based on an extensive collection program, covering various different areas of the State of São Paulo and other states in the country, for a comparison between different phytogeographic areas and their fauna composition. Five groups, four arachnids (Araneae, Scorpiones, Opiliones and Acari) and one Myriapod (Chilopoda) will be studied. The collection program will be carried out over a period of two years. Four collection methods will be used. The sampling effort will be standardized, in order to sample the arachnid and myriapod fauna of these biomes as much as possible. The sampling methodology will consist basically of manual collection, mainly at night, beating trays, pitfall traps and Winkler extractor. The collections should last for one week to ten days in each area. The material obtained will be deposited in the collections of the Instituto Butantan and the Museu de Zoologia da Universidade de São Paulo. The estimated species richness will be calculated using three methods of analysis: Log Normal Curve Fitting, Species Accumulation Curve and the Jackknife standard (JACK1-SD). These methods will be analyzed by the EstimateS5 version 5.0.1 program. The richness and abundance of spiders in each area will be compared through Analysis of Variance (ANOVA), and the difference between the groups will be detected according to Tukey Test. The project envisions a series of products on the orders of Arachnids and Myriapods, such as: inventories; ample and representative collections; computerization the collections; scientific papers; identification keys; databases for the Neotropical species; textbooks in Portuguese; training of new specialists; instructional leaflets, manual and CD-ROM on arachnids and myriapods; courses and lectures.
Araneae of Alberta and Saskatchewan, Canada
We have found a combined total of 680 species (23 families, 195 genera) of spiders in the Canadian Provinces of Alberta and Saskatchewan. The individual totals were 526 species (22 families) for Alberta and 564 species (23 families) for Saskatchewan. Of the combined total, 17% were found only in Alberta and 23% only in Saskatchewan. The dominant families were Erigonidae (25.9%), Linyphiidae (12.9%), Salticidae (9.0%), Gnaphosidae (8.4%), Lycosidae (7.4%), and Theridiidae (6.5%). For northwestern North America, these totals compare with 297 species in Yukon Territory, 484 in Manitoba, 567 in British Columbia, and 760 in Washington State.
Mass spectrometry and peptide fingerprints from the venom of the Brasilian tarantula Lasiodora parahybana
Spiders and other venomous arthropods store various complex neuroactive chemical compounds in their own venom glands which are able to paralyze and kill their prey. These venomous compounds often exhibit specific biological activities and most of them have been recognized as potent pharmalogical tools for the characterization of cellular receptors. This rich source of new peptide toxins is increasingly the focus of discovery effort in order to identify a lead for novel pharmaceutical agents or to study the structure and function of central and peripheral nervous system receptors. Arthropod toxins are often high affinity ligands as result of a refined evolutionary process which has selected highly specific toxins from natural combinatorial libraries. Besides proteins and polypeptides, a series of low molecular weight compounds, such as acylpolyamines targeting ionotropic glutamate receptors were found in spider venom glands. The characterization of whole compounds to give a complete venomous gland product fingerprint would be an efficient method for identification and classification of specimen without killing the animal. Mass spectrometry has been increasingly used in recent years to realize peptide fingerprints of animal venom from snakes, scorpions, cone shells and spiders. This technique enabled the identification of toxin mass maps which, could be used as a unique fingerprint for the systematic classification. Taking the whole compound masses into account, we presented a complete Lasiodora parahybana tarantula venom description using a combination of LC-MS and Maldi-Tof-MS experiments. This work exhibits the possibilities of species identification by mass mapping.
Redescription of the giant arachnid Megarachne servinei Hünicken, 1980 and comments about its taxonomical position
The study of fossil arachnids is fragmentary, especially from the Paleozoic Period. Megarachne servinei Hünicken was described in 1980 based on a specimen found in the Bajo de Veliz Formation, San Luis, Argentina. It was found associated with fossils of giant insects and another arachnid,s the trigonotarbid Gondwanarachne Pinto y Hünicken. Both of these arachnids represent the first arachnid fossil record from the Paleozoic Period of Argentina. M. servinei was described originally as a mygalomorph spider but its taxonomical positions had been questioned. This species does not share the synapomorphies of the Araneae and it may represents a giant ricinulid. The objective of this work is to re-describe this fossil. The holotype of M. servinei and a new well-preserved specimen found in the same geological formation were studied. New characters were studied, described and re-interpreted. These arachnid specimens are very different from other arachnids, fossil or living, therefore we propose that Megarachne servinei be placed into a new order of fossil arachnids not previously described.
Spiders associated with cotton crop in La Rioja Province, Argentina and their relationships with other arthropods
In Argentina, the study of the spiders in agro-ecosystems began about 15 years ago. Special attention was given to their diversity and their abundance on crops such as cotton, soybean, alfalfa, strawberry and wheat. Unfortunately little of these data has been published. A study of spiders in cotton agro-ecosystems started in 1999 in La Rioja Province, sited in the Central-West of Argentina. This province belongs to the biogeographical region called Monte Province and it is a semi-desert area. The aim was to study the spiders associated with cotton and their relationship with other predator and pest arthropods in agro-ecosystems under different management practices. During this study, 10 samples were taken biweekly from November 1999 to April 2000 in two different commercial plots of cotton. One under conventional management that included numerous applications of insecticide and the second was sowed over the rest of the wheat crop with few applications of insecticide. We also sampled in an area adjacent to both plots that was represented by natural secondary vegetation of the Monte Province. A total of 16 788 arthropods were collected with sweep nets, beating and pit-fall trapping. Samples were taken in 10 different points for each collecting method, randomly chosen in one hectare in each plot. All the arthropods collected are listed and the abundance and biodiversity index for each spider family, other predator arthropods and pest insects are given in comparative manner for each habitat. The importance of spiders in this agro-ecosystem is discussed.
Revision of the Afrotropical species of Selenops (Araneae, Selenopidae) with notes on their distribution
The genus Selenops Latreille has a holotropic distribution and is represented by 14 species in the Afrotropical Region. It has a wide distribution from the Sahara Desert in the North to South Africa in the South. Lawrence (1940) was the first to study the Selenops of Southern Africa while Benoit (1968) revised the species north of the 17éparallel. The aim of this study is to revise the Afrotropical species of the genus and to discuss their distribution patterns. Material from several American, European and African Museums was studied during this revision. Eleven new species are described and drawn. A key to all the Afrotropical Selenops species are provided with maps of their distribution.
Signal polymorphism in the web-decorating spider Argiope argentata is correlated with reduced survivorship and the presence of stingless bees, its primary prey
No abstract submitted
The development of a habitat quality index for forests in Flanders: a case study on spiders
A first attempt was made to draw up a habitat quality index for forest in Flanders. That this is not obvious for forests in Flanders, which are highly fragmented, is shown here. A huge sampling campaign in 40 different forests revealed that soil texture and humidity are the main factors explaining observed spider faunas. A difference could be observed between forests on sandy soils and forests on sandy loam/loamy soils. Many environmental (abiotic) parameters appeared to be linked in forests and can therefore not be treated separately, which makes the development of an index difficult. The main conclusion of our study is that the development of a habitat quality index should be linked with existing subregions in Flanders according to soil constitution. So, development of at least two indicator indices for forest stands seems appropriate on the basis of our findings. Relationships between spider faunas and single environmental parameters should be investigated in the future, while keeping as many other parameters constant as possible.
Spider faunas collected with several trapping techniques in forest reserves in Flanders, with emphasis on stem-living spiders
Biodiversity often plays an important role for forest reserve policy makers. Because only few data are available on general invertebrate diversity in forest reserves in Flanders, a preliminary investigation was started on xylobiont beetles combining several sampling techniques in four forest stands. During these samplings spiders were also caught during a whole year. Each sampling site consisted of three pitfall traps, one window trap, six pan traps (three yellow and three white), one stem-eclector and one dung-baited trap. The sampling in the four forest stands yielded more than 6300 spiders belonging to 127 species. Analysis showed that very few spiders were caught with window traps and dung-baited traps and that these species were mostly also caught with other techniques making these techniques not very suitable for spider inventories. DCA and TWINSPAN analyses showed a huge difference between species caught with stem-eclectors and those collected with pitfall and pan traps (which group together). Both trapping techniques yielded specific spider faunas, which gives a more complete picture of the spider faunas living in forests. Humidity was the second most important factor explaining the spider assemblages. These results illustrate the necessity to combine several techniques in order to get a more complete picture of the spider diversity in forests.
The South African National Survey of Arachnida (SANSA): the pseudoscorpions (Arachnida: Pseudoscorpiones)
In 1997 the South African National Survey of Arachnida (SANSA) was initiated as a national action plan to determine and protect the biodiversity of the Arachnida fauna of South Africa. One of the first steps in developing a national action plan to conserve fauna is the preparation of an inventory of species present. Of the larger arachnid orders only the scorpions of South Africa are fairly well known. During this study a checklist of the Pseudoscorpiones of South Africa was compiled. A total of 135 species and 9 subspecies of pseudoscorpions are presently known from this region, represented by six superfamilies, 15 families and 65 genera. This represents about 4.4% of the world's fauna. Of these species, 97 (71 %) have so far only been recorded from South Africa. Thirty-three species have a wider distribution pattern in the Afrotropical Region and three are cosmopolitan. Pseudoscorpions have been poorly sampled and studied in South Africa and the numbers presented here probably represents only a portion of the species present.
Spiders of the Kruger National Park, South Africa (Arachnida: Araneae)
Although spiders constitute an abundant and highly successful group of invertebrate animals, they have been largely ignored in conservation endeavors in South Africa. Conservation biologists are only now starting to recognize the importance of the invertebrate component in the functioning of healthy ecosystems. Compared with areas in the Northern Hemisphere our knowledge of African spiders is particularly sparse. Our knowledge of African spiders is largely restricted to taxonomy, and even here the surface of a rich fauna has only been scratched. As part of the South African National Survey of Arachnida (SANSA), an inventory of the biodiversity of spiders of the National Parks of South Africa is underway, with check lists of the Mountain Zebra National Park, Karoo National Park and Kruger National Park (KNP) completed. Data based on sporadic surveys undertaken in the KNP over a 15 year period has been used to compile a list of species known or new for the Kruger National Park. At present 139 species, 39 families and 111 genera are known, of which 97 species are new records for the park. Meaningful conservation cannot take place if the species involved are not known. Inventories like this is the first step in promoting spider awareness and research in the park.
Spiders, a wealth of information still to be tapped
Based on its extensive specimen and literature reference sources, the Arachnida Unit of the Biosystematics Division of ARC-Plant Protection Research Institute in 1997 launched the "South African National Survey of Arachnida" (SANSA) in accordance with the country's obligations to the Convention on Biological Diversity. The main aim of SANSA is to compile an inventory of the arachnid fauna of South Africa, which will provide essential information needed to address issues concerning the conservation and sustainable use of our arachnid biological diversity. For the first time an inventory of the spider families, genera and species known from South Africa was prepared. It was found that the araneofauna of South Africa is remarkably rich when compared to some other faunas of the world. A total of 67 of the world's spider families occur in this region represented by 430 genera and about 2950 species. Although South Africa represents only 0.8% of the world's total land area it is recognized by the World Conservation Monitoring Centre (1992) as the third most biologically rich country in the world (after Brazil, Indonesia). It contains 8 % of the world's vascular plants, 6-7 % of the terrestrial mammals and 9 % of the spiders. A review of the literature indicates that the taxonomic information on Southern African spiders is still rudimentary and only 144 genera have been revised (33 %). Not only is the taxonomic knowledge of the araneofauna still fragmentary but little is known also about their ecology, biology and behavior.
Ecological separation of orb-weavers in Ghana, West Africa
Nine common species of orb-weavers: Araneus cereolus, A. rufipalpis, A. legonensis, Neoscona nautica, Gasteracantha curvispina, Isoxya cicatricosa, Argiope flavipalpis, A. trifasciata, and Leucauge sp. were studied at Legon, Ghana. The habitat consisted of grassy areas with shrubs. The following web parameters were measured: height from ground; web diameter, mesh size and angle of inclination; light at web site. In some species the horizontal distance of the web from the vegetation and the type of vegetation in which the web was built were also measured. Another study showed that some species are entirely nocturnal while others are diurnal. From these results, it is shown that there were significant differences in at least one parameter between all species pairs. It is suggested that this would lead to ecological separation between all the species studied and also with Pararaneus cyrtoscapus reported in another study (Edmunds 1978).
Arachnida and Arachnology an Egypt
The scientific study of Arachnida in Egypt began with the French expedition of Napoleon in 1799-1801. There have been several additions since the catalogue of Cambridge (1876) and the works of Simon. The efforts of the arachnologists during old and modern periods are reviewed. A discussion of the future of this discipline is included.
Survey of the spiders of the Western Soutpansberg
By virtue of its geological history and geographical location the Soutpansberg constitutes a refuge for a disproportionately high diversity of organisms. The Western Soutpansberg forms part of a unique private initiative to conserve this internationally important conservation area and establish it as a Biosphere Reserve. As part of this initiative the spider fauna was surveyed over a three-year period. A total of 37 families represented by 83 genera and 97 species have been collected. Of the species collected 63 (64.9%) were wanderers and 34 (35.1%) web builders. A list of the species collected and information on the guilds that they occupy are provided. Observations on the distribution, diagnostic morphology and behaviour of certain species are also given. This is the first inventory of arachnids from the western Soutpansberg and the survey forms part of the South African National Survey of Arachnida (SANSA).
Variation in the stabilimenta characteristics of Cyclosa fililineata and C. morretes in southeast Brazil
The inclusion of prey remains and other debris in the orb webs constructed by spiders of the genus Cyclosa could reduce the risk of predation, resembling some object that is less attractive than the spider itself. The efficiency of this structure in disrupting the visual sign of a spider, however, probably is dependent on its size and shape. In this study we investigate the characteristics of the stabilimenta constructed by two species of Cyclosa, within and between populations, in six areas of southeast Brazil. We collected a total of 409 stabilimenta of C. fililineata and 179 of C. morretes. Both species construct stabilimenta composed entirely of silk (linear and circular types) or by silk and debris (linear; row of detritus clusters and complex types, including detritus positioned in a shape that resemble a large spider). The vertical linear type, containing detritus, was the most frequent structure for both species. However, the position occupied by C. fililineata in the detritus column is highly variable within populations while C. morretes, in some areas, occurs always in the inferior extremity of the column. The frequency of C. fililineata occupying the extremities of the column was low in all the populations. We hypothesized that the unpredictability of spider position could be important to avoid predators. Stabilimenta composed by a row of detritus clusters were more frequent in males and juveniles of C. morretes. These structures seems to be an intermediate state towards a linear type. Circular silk stabilimenta are constructed only when detritus are not available, as after web destruction. There is no correlation between the symmetry of the web and the symmetry of the stabilimentum for both species. The size of the spiders, however, is strongly correlated with both width and length of these structures.
The diversity and distribution of the Solifugae of South Africa (Arachnida, Solifugae)
About 1000 species of Solifugae are known from around the word. They are more commonly found in the warm and arid regions of the world. South Africa has a rich fauna of solpugids represented by six families: Ceromidae, Daesiidae, Gylippidae, Hexisopodidae, Melanoblossidae and Solpugidae and 147 species. This represents 14.7% of the world's fauna. As part of the South African National Survey of Arachnida (SANSA) an inventory is made of the species diversity of the solpugids of South Africa. The checklist of Lawrence (1955) is updates and addition information is provided on type localities and distribution for each species. Distribution maps are provided for each family.
Modulation of sodium channels by an alpha-toxin isolated from the venom of Buthus martensi Karsch
As key elements of signal transmission, sodium channels are the target of neurotoxins of diverse origins and chemical structures. These toxins have effects that range from pore blocker (e.g. tetrodotoxin, Ś-conotoxin) to modification of the gating and permeation (e.g. scorpion and sea anemone toxins, batrachotoxin). Toxins have proven to be invaluable tools for probing the structures of different ion channels and evaluating their physiological contribution to cell and organ behavior. Moreover, elucidation of the mechanisms of action of toxins, knowledge of their 3D-structures and the discovery of common scaffolds between toxins open wide perspectives in designing various drugs. Scorpion venoms are rich sources for small, mainly neurotoxic proteins interacting specifically with various ionic channels in excitable membranes. Scorpion toxins acting on sodium channels have been divided in two major groups, a‑ and b‑toxins, according to their pharmacological effects on Na+ currents in electrophysiological preparations and their binding properties. The Asian scorpion Buthus martensi Karsch (BmK) is widely distributed in China where it has been one of the indispensable materials used in Chinese traditional medicine for thousands of years. Its venom has been extensively studied and numerous alpha-toxins have been isolated from it. However, in most cases, electrophysiological characterizations are still lacking. The present study investigates the electrophysiological actions of BmK M1, an alpha‑like toxin purified from the venom of the scorpion Buthus martensi Karsch, on voltage‑gated Na+ channels. Using the voltage clamp technique, we assessed the BmK M1 activity on the cardiac isoform of Na+ channel (hH1) functionally expressed in Xenopus oocytes. The main actions of the toxin are a concentration-dependent slowing of the inactivation process and a hyperpolarizing shift of the steady‑state inactivation. This work is the first electrophysiological characterization of BmK M1 on a cloned Na+ channel, demonstrating that this toxin belongs to the class of scorpion alpha‑toxins. Our results also show that BmK M1 can be considered as a cardiotoxin.
Does forest fragmentation affect reproduction of the spider Coelotes terrestris (Agelenidae)?
Between August and October 1999, 10 populations of the spider Coelotes terrestris were sampled to assess possible effects of forest fragmentation on female reproductive output. Females were collected after insemination had taken place in the field and were kept in the lab at 21éC, under a day-night rhythm of 16 hours light and 8 hours darkness. After being one month under these simulated spring conditions, females started to produce egg cocoons. To assess female reproductive effort the number and mean size of the eggs of the first cocoon were determined. Both parameters were used to calculate the reproductive volume and were related to the size of the female. We found that there was a significant positive correlation between female size and number of eggs (p < 0.01), but not between female size or egg number and egg size. Females of the Zonién population had a lower egg number for a given size, although these animals were relatively larger than those of the other populations. This might be due to the negative effects of the surrounding highways and to the proximity of the capital city of Brussels.
The effect of egg parasitism by a Psyllaephaqus sp. (Hymenoptera: Encyrtidae) on the population size of Peucetia striata Karsch, 1878 (Araneae: Oxyopidae) in the Free State, South Africa
Parasitism of spiders and their egg sacs by insects is limited to a few specialist families. These are the Mantispidae (Neuroptera). Acroceridae (Diptera), and some Scelionidae, Pteromalidae, Ichneumonidae and Encyrtidae species (all Hymenoptera). In this study egg sacs of Peucetia striata (Araneae: Oxyopidae) were collected from Melolobium candicans bushes in grassland during July and August 2000, and preserved in 70 % ethanol. Ten egg sacs had a female present and 10 had no female present. The number of egg sacs infested by Psyllaephagus sp. (Hymenoptera; Encyrtidae), parasitised eggs, unfertilised eggs, developing eggs, spiderlings and wasp adults, were counted. The data showed that 5/10 egg sacs were parasitised where the Peucetia striata female was present compared to 2/10 where the female was absent. This suggests that the female may be the primary chemostimulant to which female wasps are attracted. A maximum parasitism level of 28,1% in a single egg sac was found (n=l). although most sacs were parasitised to a much lesser degree (x= 10.26%, n=7). Factors that limit frequency and level of parasitism are the small size of the Psyllaephagus sp. females (<3 mm in length) and their ovipositors (penetration), incorporation of plant debris in the egg sac structure (camouflage), and constructing the egg sacs in the core of the bush rather than the periphery. The low level of parasitism indicates that the wasps have a minimal effect in limiting the population size of the spiders.
Do Leucauge spp. adapt web characteristics in relation to prey size?
Leucauge mariana (Keyserling) and L. venusta (Walckenaer) are very common spiders in coffee plantation in Chiapas, Mexico. Those two species are morphologically similar and build a horizontal oval web between adjacent coffee plants. In this study we attempted to determine the existence of a relationship between web characteristics and prey size. The characteristics of 100 adult female Leucauge mariana/venusta webs located in a coffee plantation were measured, namely: distance ground-centre of web (cm), web diameter (cm), number of radials and number of spirals. Principal component analysis applied to these data differentiate three groups with respect to the distance ground-centre of the web; the first group (G1) had a mean distance of 54.5 +/-1.8 cm, the second (G2) a distance of 101 +/-2.3 cm and the third (G3) a mean distance of 153.8 +/-3.6 cm. For each group, the diameter of the web (around 30 cm) and the number of radials (around 35) were the same but statistical differences were detected in the number of spirals. The webs of G3 spiders had fewer spirals than the others groups (mean = 45 +/-2.2) whereas the webs of G1 spiders had many more spirals (mean = 52+/-1). Sticky traps were placed at 0.5 and 1.5 m above ground level to evaluate the abundance and size of insects caught at these two heights. A statistical comparison of insects of the same order captured indicated that significantly larger insects were caught in the traps at 1.5 meters than at 0.5 meters above the ground. I suggest that the "open" structure of the highest webs represent a response by the spider related to the average size of the prey. I will also discuss these results in terms of a behavioral adaptation related to the sexual maturity of the spiders.
Copulatory mechanics in the synanthropic pholcid spider Spermophora senoculata (Dugès)
Synanthropic animals often provide excellent objects for detailed single-species studies. Nevertheless, some synanthropic species like the pholcid spider Spermophora senoculata have virtually remained unknown. We present a detailed analysis of the behavioural sequences of copulation and of the functional morphology of the genitalia of this species. Our results are based on a variety of methods: freeze fixation of copulating pairs, scanning electron microscopy of the genitalia in functional contact, observations of copulations under the dissecting microscope, and histological serial sections of the genitalia in functional contact. The results are placed in the context of a substantial body of literature that has accumulated recently and has made pholcids the best known spiders with respect to genital mechanics.
Clinical effects in bites from formally identified spiders in tropical Australia
Objective: To determine the types of spiders causing bites and the clinical effects of their bites in tropial Northern Territory. Design: A prospective study of confirmed and suspected spider-bites and a retrospective analysis of data from standardised, local database of spider-bites. Confirmed spider-bites were those in which there was a clear history of the bite, and the captured spider was identified by an arachnologist. Subjects and data source: All subjects with confirmed and suspected spider-bite presenting to the Emergency Department or referred from August 1999 to August 2000, or identified from the database. Results: Thirty-four subjects had a confirmed spider-bite from an identified spider: 25 in the prospective group and nine in the retrospective group. The spiders were Sparassidae (12 bites), Missulena pruinosa (Actinopodidae) (7), Latrodectus (4), Araneidae (4), Salticidae (4), Nemesidae (1), Conothele (1) and Selenocosmia (1). Clinical effects were local pain in 97% (severe in 29%), redness in 47% and swelling in 24% cases. Systemic effects occurred in three victims, two of whom were bitten by M. pruinosa. There were no cases of confirmed arachnidism. Conclusions: None of the spider-bites resulted in severe effects. Compared with data from other parts of Australia, different species were involved and latrodectism was uncommon. Our study highlighted the importance of correctly identifying the spider species.
Himalayan radiation of Pseudopoda (Araneae: Sparassidae: Heteropodinae)
The recently described sparassid genus Pseudopoda is recognised (with well over 50 species) as a highly diversed group in the Himalaya. Its representatives are adapted - in contrast to their tropical relatives - to altitudes from 1500 to 3500 m. According to results from taxonomy and zoogeography, the evolution of Pseudopoda in the Himalayas is recognised as a typical mountain-radiation: swarms of neo-endemic species with strongly delimited distribution ranges are adapted to different altitudes. Parallel immigration into the Himalayas from the east to the west is suggested for Pseudopoda spp. for at least five species-groups and even within one species-group. Different evolutionary trends are recognised in male and female genitalia. Regarding to these trends two species-groups are considered highly derived. Results from zoogeography and taxonomical investigations on other sparassid genera from Asia and Africa confirm this consideration.
Do you know what family these spiders belong to? - an interactive poster!
Specimens of two clearly related species belonging to an undescribed Araneae taxon are presented. The spiders were found in the south-eastern Cape region; they are free-living ground spiders of the litter layer. The reader is invited to follow the family identification key of Dippenaar-Schoeman and Jocqué (1997) to try to come to a family identification. The conclusion of this exercise is here left open. Remarkable characters of these three-clawed taxa are the abdomen with strong dorsal scutum, provided with a frontal field of stiff macrosetae in large sockets, the absence of a fovea, the reduced spinning apparatus characterised by a reduction of the posterior spinnerets and the absence of major ampullate gland spigots, the extra frontal tooth on the chelicerae and the "hair basket" on the inner side of the chelicerae. The presence of branched lateral tracheae might indicate a relationship with the Zodariidae with which it also shares the life style. Some of the characters are illustrated by SEM-photographs. A remarkable trait is the presence of abdominal pockets in some males; these depressions apparently serve during copulation and are supposed to make a connection with the chelicerae of the females.
Mating history influences female choice in the wolf spider Pardosa agrestis (Lycosidae, Araneae)
Pardosa agrestis, being abundant in many agricultural habitats in Central Europe, is used for several years as model organism of arachnological studies in Hungary. These studies have revealed that the duration of mating in this species (2-3 hours) is much longer than needed for complete fertilisation. In addition P. agrestis females can mate more than once, in which case mating order is not a decisive factor of sperm priority. Given the possibility of multiple mating, we tested how mating history and male quality affects female readiness to mate. We compared the behaviour of unmated, mated and "incompletely mated" females. Females belonging to this latter group have previously undergone a mating artificially interrupted after 15 minutes. In the experiment two qualities of the males were known: body weight and radiation history (part of the males were irradiated with 30 grey X-ray for latter use in sperm precedence experiment). Couples were paired randomly, and the occurrence of mating was observed (duration of observations were between 2 to 8 hours). Out of the 1545 trials 320 mating events occurred (22%). Data was tested with survival analysis. Unsuccessful trials were included in the analysis as censored cases. The chance of mating did not change significantly with time. Survival analysis showed, that virgin and incompletely mated females needed significantly less time to mate than mated ones. We found no significant difference between incompletely mated and unmated females. In case of virgin and incompletely mated females none of the male qualities have influenced significantly the chance of mating. However, in the case of mated females we found significant difference between the mating success of irradiated and non-irradiated males and significant positive correlation between the male bodyweight and the mating chance. Body weight is a straightforward indicator of male quality. Irradiation caused no changes in males that would have been observable for us, but we interpret the results, that this treatment caused a change in some quality of the males, that was noticeable for female spiders. The results suggest that virgin females are more ready to mate, while females which have already mated once, needed longer time to remate, and become more choosy concerning male qualities. The fact that after an incomplete mating the chances of a second mating remain high, but after a long mating they decrease, might be an explanation why males try to mate for long durations, suggest an runaway process for the evolution mating duration in P. agrestis.
P. T. Lehtinen Biodiversity Centre for University of Turku, 20014 University of Turku, Finland
Polyphyly of Thomisidae: Dietinae auct.
The only character uniting genera of Dietinae Petrunkevitch, 1928 is the presence of tarsal claw tufts, an adaptation to movement on large leaves and other smooth surfaces, is not a synapomorphy. The only New World species Browningella browningi Mello-Leitao, 1948 is not closely related to Dietini or any other group of Dietinae auct. The Old World genera of Dietinae belong to three thomisid lineages. The genera of Dietini are relatives of Thomisini in Thomisinae. Alcimochthini and Amyciaeini are relatives of Tmarini. Apyretini, Emplesiogonini, and Mystariini are closely related to each other and to Tagulini from Thomisinae. Together they consist of a new suprageneric taxon with three subgroups Tagulini, Apyretini and Mystariini. Some genera of Simon's other tribes are also included. Pactactes Simon, 1895 is transferred from Pagidini close to Nyctimus (Apyretini) and Platypyresthesis Simon, 1903 from Diaeae Simon, 1895 (Misumenini sensu Ono 1988) to Mystariini and synonymized with Sylligma Simon, 1895. The enlarged tribe Talaini sensu Ono is not accepted. Lysiteles Simon, 1895 is also excluded and the single genus Talaus with its synonyms Microcyllus and Taypaliito Barrion, 1995 is left. Haedanula Caporiacco, 1941 is transferred from Stephanopinae Hedanini to Mystariini. Cymbacha simplex Simon, 1895 from Sri Lanka is excluded from the purely Australian tribe Cymbachini and transferred to Mystariini. Only the new suprageneric taxon is presented here in more detail. There are two excellent synapomorphies for this group. 1: Presence of marginal or submarginal strong setae on raised tubercles in the thoracic part of carapace in irregular groups or in marginal rows. 2: An unique eye pattern on short and wide carapace. Whitish or pale femora III-IV are a synapomorphy for Apyretini and Talaini and small lateral eyes for Mystariini. The genital organs of both sexes have various autapomorphies in different groups of genera. At least Talaini are jumping spiders as salticids. A possible sister group for this new group is the Australian-Melanesian Porropini with no special setae on carapace and no white areas on legs. This group is restricted to the Old World and its main speciation centre is in Madagascar (Apyretina, Pseudoporrhopis, Emplesiogonus, Lampertia and Soelteria) and tropical continental Africa (Tagulis, Pactactes, Mystaria, Sylligma, Paramystaria, Hewittia and Haedanula). Four genera (Talaus, Tagulinus, Nyctimus and Zametopina) occur in southeast Asia. Absence of preserved material makes the placing of some genera impossible (Tarrocanus, Plastonomus and Peritraeus), as well as for Diplotychus and Scopticus from Dietini auct.
Sequencing the California (USA) scorpion fauna: a preliminary investigation into the phylogeny and biogeography utilizing the 16s mitochondrial gene
A preliminary phylogenetic review of some California (USA) scorpions is presented with analyses based on 16s mitochondrial gene sequences. The purpose of this poster is to present preliminary data addressing the Williams and Savary (1991) conclusions that the genus Uroctonus Thorell, should be restricted to include only three named species, all of which occur in California, and that the genus Uroctonites Williams and Savary (1991), shares a more recent ancestry with Uroctonus than it does with other California taxa (including Pseudouroctonus Stahnke and Vaejovis Koch). Ultimately, this study will expand the number of taxa sequenced in order to compare and contrast morphological characters with molecular sequences in hopes of finding robust and phylogenetically informative conclusions regarding California scorpion systematics.
An evaluation of the possibilities to incorporate spiders in a monitoring scheme for wet heathland habitats
To be able to evaluate on a regular basis the results of nature conservation efforts, monitoring systems should be designed. Abiotic and biotic indicators of the evolving nature value and biodiversity as a result of nature management measures will have to be tested and evaluated for what concerns their possibilities in that respect. The aim of our contribution is to investigate and to evaluate if and how spiders can be used in that context of applied ecological research. Indicator potentiality as well as practical feasibility is considered.
Diversity of spiders in boreal and arctic zones
Spiders are one of the best objects to study and monitor species diversity in terrestrial ecosystems, especially at high latitudes, because of 1) their commonness in all types of biotopes, 2) high or highest species diversity (within arctic macroarthropds), and 3) easy methods of collection. The last two decades have been marked by considerable growth of taxonomic and faunistic publications dealing with Arctic and Subarctic spiders both in Palaearctic and Nearctic. Almost or entirely unknown faunas of Polar Ural, Krasnoyarsk Province, Yakutia, NE Siberia, Tuva, Yukon Territory have become rather well known due to several catalogues and check-lists. More than 300 spider species have been described from Arctic and Boreal zone of Asia and North America during the last 15 years. Such growth of information makes possible to analyze basic pattern of spider diversity in North Holarctic. Although number of species found in faunas north of 60éN varies from 620 (Finland) to 300 (Yukon T.), species lists of each fauna allow to show most interesting and important areas of species diversity. Only two areas, divided by the Bering Strait, namely NE Siberia and NW North America have rather big proportion of endemic taxa (around 8%) belonging to several spider families. Similar level of endemism was found also in some groups of insects (11% of row-beetles are endemics in NE Asia). No other area north of 55éN incorporates more than 1% of endemic species. High level of endemism, together with rather high known species diversity in NE Siberia (550) and NW Nearctic (about 500) and inadequate level of investigation of these areas show high necessity of further study of these areas. Study of species composition in more than 20 northern local faunas reveals that Lycosidae species percentage in each local fauna varies in smallest range (8-12%) in comparison to other families. This feature as well as some others allow to use wolf-spiders as a good indicator of general species diversity of spiders in local faunas.
The effect of chelicera length on the outcome of male-male fighting in the ant-mimic spider, Myrmarachne japonica (Araneae; Salticidae)
In Myrmarachne japonica (Araneae, Salticidae), the sexual dimorphism in chelicera length is a prominent character at an adult stage; males have a longer chelicera than females. However, at a sub-adult stage, this sexual dimorphism was unclear in appearance. The allometory slope between the cephalothorax width and the chelicera length in males was significantly more than 1.0, and is higher than that in females. This pattern suggested that sexual selection affected the evolution of longer length of male chelicera. To elucidate the function and the biological role of the longer chelicera in males, I tested the effect of chelicera length and cephalothorax width on the outcome of male-male fighting. Chephalothorax width was used as an index of its body size. When the difference of chelicera length of opponents was large, the fighting terminated at the low escalation level of fighting. When the difference of chelicera length was small, the fighting escalated. However, there was no correlation between the difference of chelicera length and its fighting duration. And the difference between their cephalothorax width did not affect its outcome. Consequently the chelicera length of males has a function of an indicator of male fighting ability and the effect of chelicera length on the out come of male-male fighting was stronger than that of its body size in M. japonica.
Antibacterial properties of a pore-forming peptide in the venom of Parabuthus schlechteri
Pore-forming and/or membrane destabilizing peptides are part of the venom of bees, wasps, some ants and spiders and they contribute to the innate defense mechanism against bacterial and fungal infections in most animals. In addition to a role in the defense against microorganisms, they also function as offensive chemicals: the virulence of a series of pathogenic bacteria depends on the activity of similar membrane disrupting substances. Recently we found evidence for the presence of pore-forming substances in the venom of scorpions and could identify a peptide in the venom of Parabuthus schlechteri (parabutoporin, PP) with mastoparan- (present in the venom of wasps) and melittin- (present in bee venom) like activities in white and red blood cells. It belongs to a group of cationic, amphiphilic, a-helical peptides that exert cytotoxic activity in eukaryotic cells and some of which have potent antibacterial activity. In this study a comparison was made between the growth inhibiting activity of synthetic PP, mastoparan and melittin on gram-positive (gram+: B. subtilis, S. aureus) and gram-negative (gram-: E.coli, P. aeruginosa) bacteria and and their effects related to hemolytic activity on human red blood cells. PP was the most potent growth inhibiting peptide on gram- bacteria but the least active on gram + bacteria. The order of potency of hemolytic activty was: melittin > PP > mastoparan. The minimal inhibitory concentration for 100 % suppression of bacterial growth in gram- bacteria by PP was about 1 ŚM, the concentration for 50 % hemolysis about 30 ŚM. Although these results may suggest a high prokaryote/eukaryote activity index, we found that human granulocytes and dorsal root ganglion cells of the rat are also affected at low concentrations in the micromolar range (see Abstract Verdonck et al.). The potent action on gram- bacteria can be related to the high amount of positive charges (lysin residus) present in the peptide. In conclusion: we could show that cysteine-free, cationic, amphipathic peptides with antibacterial activity occur in the venom of Parabuthus scorpions. Antibacterial peptides may protect the venom glands and its content against infection.
The effects of feeding conditions and maternal care on reproductive traits in theridiid spiders
No abstract submitted
How do salticids mimic ants?
It is often assumed that ants and spiders are mutual predators. However, whether ants attack and kill salticids they encounter has been little studied. In this study interactions were set up between individual salticids and ants. It was found that ant-eating (myrmicophagic) salticids survive all such encounters. It was also found that salticid ant mimics (Myrmarachne) have higher survival rates than most non-ant-like, non-myrmicophagic salticids. These results suggest that ant-like and myrmicophagic salticids have behavioural adaptations enabling them to avoid ants more effectively than non-ant-like salticids. Possible reasons why Phintella piatensis, a non-ant-like, non-myrmicophagic salticid had significantly higher survival rates than other non-ant-like and non-myrmicophagic salticids are suggested. These results attest to the importance of ants as predators of salticids and provide information regarding the nature of possible associations between Myrmarachne, P. piatensis and ants. Having established that ants are predators of salticids, M. assimilis, a mimic of the ant Oecophylla smaragdina, and the non-specific mimic M. bakeri were tested with Portia labiata, an araneophagic salticid, to find out whether Myrmarachne gain protection from visual predators through their resemblance to ants. Portia avoided ants and M. assimilis, but not M. bakeri. In tests with nine species of normal (non-myrmicophagic and non-araneophagic) salticids M. bakeri was avoided by two species while all nine avoided M. assimilis. These results support the hypothesis that, for Myrmarachne spp., close resemblance to ants confers protection from visual predators. The question of how M. bakeri maintains an evolutionary advantage by resembling ants remains largely unanswered, however, M. bakeri appear to be highly polymorphic. Distinct variations in colour, glossiness and patterns are common. M. bakeri differs from other polymorphic ant-like spiders because they are polymorphic before adulthood. Morphological changes appear to have no set archetype and few spiders revert to morphs previously observed. How this occurs is, as yet, a mystery as neither moulting nor environmental factors, such as light and temperature, appear to have a significant effect on individual variation. Perhaps polymorphism is a mechanism to increase mimetic defence?
M. Paulsen P.O. Box 9783, Elsburg 1407, South Africa
Behavior of the trapdoor spider Idiops fryi (Purcell, 1903) (Araneae: Idiopidae)
Idiops fryi (Purcell 1903) is a trapdoor spider commonly found in the Gauteng Province of South Africa. This is the first observation made in the field on their general behavior. Information is provided on the burrow and trapdoor structure, prey capture, disposal of prey remains and body waste. The mating procedure will be described.
The true taxonomic position of the genus Neoscotolemon Roewer, 1912, and its implication in the systematics of the Stygnommatidae (Arachnida, Opiliones, Laniatores)
Until the present, Neoscotolemon Roewer, 1912, was considered a member of the family Phalangodidae, subfamily Phalangoninae. The study of the holotype of the type species of Neoscotolemon (Scotolemon pictipes Banks, 1908) and the holotypes of Phalangodes spinifera Packard, 1888, Rula cotilla Goodnight & Goodnight, 1945, and Rula bolivari Goodnight & Goodnight, 1945, revealed that all these holotypes correspond to valid species, which must be included within the Neoscotolemon. It is also revealed that the genus must be transferred to the Stygnommatidae; which up to now was considered to be monogeneric. Evidence is presented that suggest the necessity of a systematic overhaul of the Stygnommatidae including the study of the morphology of the male genitalia and a reexamination of their extensive synonymies. The Stygnommatidae as currently presented in the literature consists of about 30 species from the Neotropics.
Diversity of arachnids of Parque Estadual da Serra da Cantareira, São Paulo, Brazil
The Parque Estadual da Serra da Cantareira is the largest urban forest in the world with 7,916.52 hectares. The region is covered by Atlantic Rain Forest and totally surrounded by urban development. In some areas, the forest was cut down and replaced by Coffea arabica and other plantations. Sampling is being carried out every two months, since August 2000, in three areas of different environmental impact: a Central area, with 60 years of forest regeneration; Pedra Grande, with 40 years of forest regeneration; and Pinheirinho, where only mild impact has occurred (only some of the large forest species were removed). The following collecting methods are being used: pitfall traps (50/area, 7 days every two months); Winkler extractor (20 m2/area, every two months); beating tray (16 samples/area every two months); nocturnal manual search (12 samples/area, every two months). Species richness will be presented for ACE, ICE, Chao 1, Chao 2, Michaelis-Menten runs, Jacknife 1 and Jacknife 2 methods (performed with EstimateS 5.01 computer program). Eleven opilionid species and one scorpion species Thestylus glazioui (Bertkau) were collected. Twenty spider species were collected in ground surface samplings (pitfall traps and Winkler extractor methods), and more than 100 with beating tray and nocturnal manual sampling.
Annual differences in peatbog spider communities: examples from Lithuania and Finland
Material of three peatbog habitats in Lithuania and one in Finland was analysed to detect year-to-year differences in spider communities. Material was collected by pitfall traps during two years. Marked annual changes in the structure of community were found when all species were included into analyses. A more stable figure of peatbog spider communities was obtained when the sets of more abundant species (>0.5 % of all specimens, i.e. 3 - 5 or more inds. in a community/year) were used in comparisons. This group of spiders represented usually 53 - 72 % of species and up to 98 % of specimens in a community. Only 3 - 9 % of these species were found during a single study year. Annual differences were caused mainly by the appearance and disappearance of species represented by only one or two specimens. Marked annual differences in abundance were recorded among the following abundant species: Pardosa sphagnicola, Drassyllus pusillus, Scotina palliardi, and Agyneta cauta in Lithuania; and Arctosa alpigena, Bathyphantes gracilis, Antistea elegans, and Drassodes pubescens in Finland. In general, stenotopic peatbog species had low annual variation in abundance when compared to species with wide range of habitats. Due to great variation in abundance of some typical peatbog spiders (Pardosa sphagnicola, Scotina palliardi, Theonoe minutissima, and Walckenaeria alticeps) between study years, two-year collecting periods is recommended in detailed community analyses or in bioindicator studies.
New species and records of Scytodes Latreille of the "globula group" from Brazil (Araneae, Scytodidae)
The scytodids consist of a small spider family with only three genera. The family has a worldwide distribution but only species of the genus Scytodes Latreille have been recorded in the Neotropical region. They are commonly known as "spitting spiders" due to a characteristic hunting manner in which they eject a sticky substance through external openings in the chelicerae fang. Most are nocturnal, hiding during the day in holes or crevices, or lying flat against the substrate. The genus has been intensively studied during the last three years in Brazil and includes to date, 15 species. Of these, 11 are described exclusively for the country. Scytodid species are separated mainly by morphological characteristics of the male palp and female epyginum. For the genus Scytodes, the male palp enabled a preliminary separation of at least one distinct group, here designated the "globula group". The group is diagnosed by the presence of a large and curved sclerotized process on the distal area of the bulb. It includes the synanthropic species Scytodes globula Nicolet and Scytodes itapevi Brescovit and Rheims plus four new species, here described. One from Xapuri in the state of Acre, one from Niqueléndia and one from São Domingos, both in the state of Goiás and one from Aripuanã, in the state of Mato Grosso. In addition new records, for the previously described synanthropic species, are presented.
Notes on the Neotropical Hersiliidae (Araneae, Hersiliidae)
Hersiliidae is a small family of mostly long-legged, cryptic spiders characterised by very elongate, cylindrical posterior lateral spinnerets. These spinnerets present the terminal segment very elongated, sometimes surpassing the length of the entire abdomen. The family is composed to date, of seven genera distributed over the tropical, subtropical and warm temperate zones of the world. The genus Tama Simon is the most widely distributed and the only one registered for the Neotropical region, from Mexico to Argentina. According to the latest spider catalogue the genus includes 23 species of which 18 are exclusively Neotropical. We here present a preliminary revision of the Neotropical species of the genus Tama. Of the 18 original species, three were described based on juvenile specimens and five have lost or unavailable type-specimens. They are thus, not considered in this study. Of the remaining ten species, only six are considered valid and are here redescribed. Two species are synonymyzed with T. crucifera Vellard, one with T. pachyura Mello-Leitão and one with Tama mexicana (O.P.-Cambridge). Two of these certainly don't belong to the genus Tama. In addition, two the males of T. pachyura and T. vittata are newly described.
Estimation of population density of common spider species from the family Ctenidae (Araneae) in Eastern Ivory Coast rainforests
The density estimation of nocturnal rainforest arthropods poses several methodological difficulties, and very few such studies were done to date. African representatives of the family Ctenidae are relatively large bodied predators with exclusively nocturnal activity. The most efficient way these animals can be collected is by hand, after having been spotted with headlamps, exploiting the reflective character of their eyes. To be able to perform a density estimation of ctenid populations, the head lamp method was employed in a distance sampling protocol carried out on 100 m long transects. Ctenidae were sampled in three Ivory Coast rainforests in three successive years (1993-1997). The total distance of transects was more than 5 km (61 transects). Approximately 2600 spiders were caught, and individually stored for laboratory identification. Seven of the 15 species encountered were common enough to have their density assessed. The presentation discusses the applicability of distance sampling to different size classes of ctenids, and separate density assessments are given by species. The overall mean density of Ctenidae in "typical" rainforest situations was 0.29 individuals/m2. This figure is evaluated in relation to the fact that ctenids are arthropod top predators in rainforest ecosystems, with an expected strong effect of intraguild predation on the populations.
A revision of the Neotropical species of the lynx spider genus Peucetia Thorell 1869 (Araneae: Oxyopidae)
The spider genus Peucetia includes 54 species of medium-sized spiders and has a global distribution. These spiders occur in the foliage of shrubs or trees, hunting activelly for insects during the day. The majority of the species of the genus occur in the tropical regions, but only the African fauna has been recently revised. In the neotropical region 24 species were described, of which 15 are here synonymyzed. Peucetia tranquillini Mello-Leitão 1922, P. rubrigastra Mello-Leitão 1929, P. meridionalis Mello-Leitão 1929, P. villosa Mello-Leitão 1929 and P. viridisternis Mello-Leitão 1945 with Peucetia flava Keyserling 1876. Peucetia similis Keyserling 1876, P. amazonica Mello-Leitão 1929, P. heterochroma Mello-Leitão 1929, P. maculipedes Piza 1938, P. trivittata Mello-Leitão 1940, P. duplovittata Mello-Leitão 1941 and P. roseonigra Mello-Leitão 1943 with P. rubrolineata Keyserling 1876. Both species are extremelly common, occurring from Colombia to Northern Argentina. Peucetia macroglossa Mello-Leitão 1929, recorded only from Central Brazilian Amazonia and Guiana is considered a senior synonym of P. melloleitaoi di Caporicacco 1947. Two species occur from Southern USA to Northern Colombia: Peucetia viridans (Hentz 1832) and P. longipalpis F.Cambridge 1902. The former is recognized as a senior synonym of P. poeyi (Lucas 1857), P. bibranchiata F. Cambridge 1902 and P. rubricapilla Petrunkevitch 1925 and the later as a senior synonym of P. cauca Lourenéo 1990. Peucetia caldensis Garcia-Neto 1989 are synonymyzed with Tapinillus longipes (Tacznowskii 1872). Two new species are recognized, one from Eastern Ecuador and the other from St Croix, Virgin Islands. The type specimens of two species described from Central America, P. quadrilineata Simon 1891 and P. thalassina (C.L. Koch 1847) are lost. Since their original descriptions are not sufficiently clear for their recognition, these are considered species inquirendae.
On the spider genus Oecobius Lucas, 1846 in South America (Araneae, Oecobiidae)
The spider genus Oecobius is composed of 79 species, and occurs all over the world. It is mostly known for some widely distributed and synanthropic species. Complete revisions are available only for African, Northern and Central American, Mediterranean and Macaronesian faunas. We revised the South American material of the genus available in several collections and found three synanthropic species: O. navus Blackwall, 1859, O. concinnus Simon, 1893 and O. marathaus Tikader, 1962. O. fluminensis Mello-Leitão, 1917, described from Brazil, and O. trifidivulva Benoit, 1976, from Zaire, are synonymized with O. navus originally described from the Canarian Islands. Two other Brazilian species, O. hammondi Mello-Leitão, 1915 and O. variabilis Mello-Leitão, 1917 are confirmed as junior synonyms of O. navus. O. marathaus, originally described from India is recorded for the first time for the Neotropical region and considered a senior synonym of O. inopinatus Wunderlich, 1995, from Australia. Distribution and habitat records for these species are provided.
Systematic revision of the Neotropical genus Lurio Simon 1901 (Araneae, Salticidae)
Lurio Simon 1901, which occurs in the Neotropical region only, was described on a single species, Hyllus solennis C.L.Koch 1846. L. crassichelis Berland 1913, L. conspicuus Mello Leitão 1930, L. splendidissimus Caporiacco 1954 and Attus lethierryi Taczanowski 1872 were included in the genus afterwards. As a result of the present revision, based on type specimens and undetermined collections from Argentina, Brazil, Panama and the USA, Lurio now comprises four recognizable species and two species inquirendae. Four synonymies and a new combination are stated, a new species is described and one species is excluded. From the five species mentioned above, only L. solennis and L. conspicuus belong to this genus beyond doubt. L. splendidissimus and L. crassichelis are here considered as species inquirendae; the type specimens are missing, and from the original descriptions it is not possible to recognize the species as new entities. Attus lethierryi, transferred to Lurio by Caporiacco (1948), is excluded from the genus, for it has been misidentified and its inclusion in Lurio is here considered a mistake. Paraphidippus validus Chickering 1946, Phidippus hingstoni Mello Leitão 1948 and Tutelina purpurina Mello Leitão 1948 are junior synonyms of L. solennis. Dendryphantes laetabilis Peckham and Peckham 1896 described on a male and Metaphidippus cupreus F.O.P. Cambridge 1901, based on a female, are conspecific; the synonymy of both names is duly stated here and the species is transferred to Lurio, the new combination being L. laetabilis. Both sexes of the new species are described. Redescriptions and new records are provided.
Phylogeny of Araneae: the fossil evidence and its interpretation
A phylogenetic tree combining all known fossil spider records with cladograms of Recent spider families is presented. This diagram reveals a number of interesting features. First, we rely heavily on Fossil-Lagerstétten (exceptional occurrences of well-preserved fossil fauna) for the fossil record of spiders; by their fragile nature, spider fossils define the occurrence of a Lagerstétte. Second, the vast bulk of fossil spiders occur in Cenozoic strata, because of their common occurrence in amber of that age (mainly Baltic and Dominican Republic). Most modern spider families, and a few fossil ones, occur in Cenozoic strata (i.e. less than 65 Ma in age). Third, there are very few Mesozoic and Palaeozoic spiders, known mainly from single specimens or a few from a single locality, but they tell us a great deal about the evolutionary history of the Araneae. Most Mesozoic spiders belong in modern families, and a picture is emerging of great longevity of many spider families. Fourth, it is rational to concentrate on Mesozoic spiders in order to fill out our knowledge of the geological history of Araneae and, fortunately, many new specimens are coming to light from strata of this hitherto dark age in the history of spider evolution.
Slovenian Araneology
The history of araneology in Slovenia and the status of the knowledge of the spider fauna at the turn of the millennium are presented. During the last six years considerable effort in spider faunistics has revealed 78 species new to Slovenia. However, Slovenian spider fauna is still poorly known and the number of spider species (currently at 531) is expected to rise dramatically as new data are gathered. Some faunal peculiarities from diverse regions of Slovenia are presented. Spider community structures have been investigated in four Slovenian forests with a standardized quantitative sampling protocol. The resulting species richness estimates allow comparisons with spider faunas worldwide. Finally, a complete bibliography of the Slovenian araneological literature is given.
The dynamics and distribution of spiders (Araneae) in brassica crops
Agrochemical control of pests is important for increasing crop yields, but there have been recent concerns about associated pollution and increased pest resistance. Consequently, both farmers and pesticide manufacturers are moving away from a total reliance on chemical control. Integrated pest management (IPM) not only targets pests with specific pesticides at appropriate times of the year, but also incorporates cultural approaches that encourage natural predators of crop pests. It is currently thought that the creation of semi-natural field margins provide refuges for a variety of predatory species that will move through the crop hunting for pest species. Spiders include many species that not only hunt on the ground, but also climb within plants to catch prey. This habit, together with their abundance within crops, suggests that spiders have considerable potential as beneficial invertebrates within IPM systems. Although evidence suggests that field margins can have high levels of such predators, few studies have examined whether these species actually move substantial distances into the crop. Recent evidence for carabid beetles has identified differing strategies across species, with some being virtually restricted to the field and crop margins, whilst others are almost exclusively field species and rarely utilise the margins. For most polyphagous predators, including spiders, it is unclear whether individuals of those species that are found in both margins and the field move between the two habitats or whether separate subpopulations exist. This study examines the distribution of spiders in several brassica crops in relation to the field margin, crop edge and field habitats, and identifies the species that are most likely to be found foraging deep into the crop. The results are discussed with reference to spiders as potential agents in IPM strategies.
The relative dependency of web spiders on grazing food chain vs. detritus food chain
Recent studies have shown that organisms derived from the detritus food chain are consumed by predators which were considered to be members of the grazing food chain. Such detrital infusion into grazing food chain seems to be common in nature (Polis and Strong 1996), although convincing evidence is still lacking. Under the condition where in situ productivity was very low, predators depend strongly on food supply from detritus food chains (e.g., Polis and Hurd 1996). However, the relative dependency on the two food chains for terrestrial predators would be changed by various factors such as environmental heterogeneity. Also, even in the same environment, differences in the foraging strategies among species may alter the relative dependency. To clarify the relative importance of grazing and detritus food chains, we examined prey captured by various web spiders living in three types of environments; inside the forest of Cryptomeria japonica, edge of the forest facing grassland, and grassland. Insects collected from spider webs were classified into at least family level to identify to which food chain they belong. We will show the variability of the dependency on detritus food chain and consider the reason for the variation.
The abundance and distribution of spiders in the South African citrus ecosystem
Spider populations were surveyed in citrus orchards in winter and summer during 1998 and 1999 in order to investigate spider population dynamics and to identify spiders with pest control potential. Surveys conducted in sites at Hectorspruit, Nelspruit, Marble Hall and the Sundays River Valley showed that spider numbers fluctuate according to season and pesticide application intensity. A dramatic decrease in web-living spiders occurred between the winter and summer surveys in all sites with significant numbers of these spiders. Numbers of spiders collected from the foliage and the ground were influenced by pesticide spray applications. Farms with minimal pesticide use yielded an average of 89% more of these spiders than those with higher pesticide usage. Three different sampling methods, pitfalls, beating and hand collecting from webs, were used to collect spiders from different habitats. Considerable overlap of families occurred between the sampling methods with pitfalls accounting for 28 families, beating for 22 and web-collection for eight. More than 2750 spiders were collected representing 33 families. Of these 219 were morphologically different and probably represented separate species. Seventy-three of these were successfully assigned to species whereas 103 were identified to genus level. Although the familial diversity was extensive, Lycosidae (22.5%), Araneidae (21.4%), Theriididae (9.8%), Salticidae (7.4%), Thomisidae (7.2%) and Linyphiidae (7%) made up over 75% of all specimens collected. Each of the remaining 27 families were represented by less than 5% of the total number collected. Most species were site-specific with 147 probable species occurring at only one site each. Fifty species occurred at two, sixteen occurred at three, three at four, and three species occurred at five of the six sites. Pardosa crassipalpis (Lycosidae) was the most widely distributed species with 94 specimens collected from five sites.
Ontogenesis of the venom vesicle of Euscorpius carpathicus (Scorpiones, Chactidae)
The venom vesicle organisation of the adult scorpion is formed by two separate glands with unfolded epithelium which are surrounded by a muscular layer in the internal half and on the ventral side. Glandular cells are of the mucous and serous type. The latter differ in the size and the aspect of the secretion granules. Some crystals are found either in the cytoplasm or in the lumen. On the basal part, one can observe replacement cells and glial and nervous intricated elements. The excretory canal of each gland is lined by a cuticular epithelium which opens at the subterminal point of the sting. On the sting, numerous sensilla that are probably mechanoreceptors can be observed. The same glands have a very different aspect in the embryo. At late embryo stage, they look like undifferentiated epithelial cells undergoing numerous mitosis; the two canals already exist but open directly outside as the sting has not yet lengthened. At the first post-embryonic stage (pullus), glandular cells have clearly differentiated and the muscular layer is already present. The gland canals have undergone anticipated ecdysis. Excretory pores although existing are not functional. As development proceeds, glandular cells grow numerous and larger. The fact that granules are never present in the lumen after ecdysis means that the gland has emptied at each molt. An electrophoretic as well as an enzymatic analysis of the components of the gland show that the enzymatic activity is only observed at juvenile stage 2 (post-pullus) after the first meal, although the proteins are already present at the previous stage.
High incidence of gynandromorphs in a tetraploid parthenogenetic (probably facultative) harvestman, Leiobunum globosum (Arachnida, Opiliones)
Leiobunum globosum Suzuki, 1953 and its close relative, L. manubriatum Karsch, 1881 are common harvestmen in woodlands of northern Japan. Females of the two species can reproduce parthenogenetically, and the males are extremely rare in the northernmost area of Honshu, and Hokkaido, exhibiting a typical pattern of geographic parthenogenesis (Tsurusaki 1985). Various kinds of circumstantial evidence suggest that thelytoky in these species are of automictic and facultative type (that is, a single female can reproduce both bisexually and parthenogenetically). Chromosome analyses revealed that L manubriatum consists of tetraploid race (usually females alone, 2n=4x=48é; only a single male has been found) and diploid race (males and females, 2n=24), whereas L. globosum includes tetraploid individuals alone (males and females, 2n=4x=48é). It is remarkable that male L. globosum also showed tetraploidy, because polyploid bisexual species are extremely rare in animals. Suzuki (1980) described as many as four cases of gynandromorphism in L. globosum. Considering the fact that until that time only 12 males had been collected in this species, it must be said that the frequency of gynadromorphs is extraordinarily high. I report here six additional cases of gynandromorphs of the species, two of these are laterally mosaic individuals, while the others are irregular gynandromorphs with the male tissue occupying only small fractions of the body. It is interesting that records of gynandromorphs concerns L. globosum alone, and no comparable phenomenon has been found in L. manubriatum. This situation can be explained by the fact that only L. globosum is a tetraploid species that presumably performs automictic thelytoky, if these gynadromorphs were produced by the partial fertilization of binucleate eggs (binucleate state is inevitable in the process of automictic parthenogenesis) by spermatozoa bearing male determinant(s). Fertilized nucleus of the egg would develop into normal male tissue of L. globosum, while unfertilized nucleus having only two genomes would also safely develop and differentiate female tissue. On the other hand, in diploid L. manubriatum under the same condition, unfertilized nucleus would not develop further because it contains only one genome. Thus gynandromorphs would not be produced in L. manubriatum.
Spiders in South African cotton fields: species diversity and abundance (Arachnida: Araneae)
Between 1979 and 1997 spiders from five cotton-growing areas in South Africa were collected. Thirty-one families, represented by 93 genera and 127 species were recorded. The Thomisidae were the richest in species (21) followed by the Araneidae (18) and Theridiidae (11). The most abundant spider species were Pardosa crassipalpis Purcell of the Lycosidae, Enoplognatha sp. of the Theridiidae, Eperigone fradeorum (Berland) a linyphiid and Misumenops rubrodecorata Millot a thomisid. The wandering spiders constituted 61.5% of the spider fauna collected and the web dwellers 38.5%. Information on guilds, abundance and distribution are provided for each species. This survey forms part of the South African National Survey of Arachnida (SANSA) in agro-ecosystems.
The shorter juvenile phase of the tuberosus male morph as possible compensation mechanism for the reproductive advantage of the gibbosus male morph in the dwarf spider Oedothorax gibbosus (Blackwall, 1841) (Erigoninae, Linyphiidae, Araneae): application of the Q10 rule
The females of the dwarf spider Oedothorax gibbosus have the possibility to choose between two male morphs: gibbosus with a protuberance on the last third of the carapace, anterior to which is a deep notch surrounded and filled by long black silky hairs and tuberosus without these features. Because of the genetic dominance (Maelfait et al., 1990; Vanacker, 1999) and a possible greater sexual attraction of gibbosus males it is expected that gibbosus would be become the most numerous morph and eventually outcompete the other morph. To explain the stability of the male dimorphism and the interdemic variation a compensation mechanism in favor of the tuberosus male is needed. The significantly shorter juvenile phase of tuberosus is a possible compensation mechanism. The juvenile phase of gibbosus males is significantly longer than that of tuberosus males and this is probably necessary for the production of the hairy groove, which probably needs a high investment. One can demonstrate this last by application of the Q10 rule on the juvenile phase of both morphs. According to Prosser (1973) Q10 is the factor with which the rate of a physiological process increases in response to a temperature rise of 10éC. One can demonstrate on the basis of the Q10 rule that the advantage of tuberosus males would be greater if it is colder and the gibbosus males have more advantage if it is warmer. To test this hypothesis, the development of Oedothorax gibbosus is observed at different temperatures. Other possible compensation mechanism of tuberosus males are sex ration distortion in favor of the female sex in tuberosus- genotypes and a better resistance against some environmental factors such as desiccation.
Araneomorph spiders from the Southern Carnarvon Basin, Western Australia: a consideration of regional biogeographic relationships
Western Australia encompasses a vast array of environments, from the temperate forest of the south coast, the tropical vine thickets of the Kimberley, to the arid deserts of the centre. Several broad-scale ecological studies have been conducted in the region, but these have historically focussed on vertebrates and vascular plants. As part of a comprehensive survey of the Southern Carnarvon Basin, situated in mid-coastal Western Australia, many different biotic groups were surveyed and their distributions analysed. We analysed the ground-dwelling araneomorph spider assemblages of the region through the use of 12-month pitfall trap sampling. A total of 33 families were detected. Apart from the Gnaphosidae and Zodariidae which were not analysed due to time-constraints, we recognized a total of 285 species placed in 146 genera. Very few taxa could be assigned to existing genera or species, reflecting poor taxonomic knowledge of many groups of spiders. Patterns in species composition across the study area were strongly correlated with rainfall gradients, and a discrete claypan fauna was detected. Vicariance events seem to explain part of the patterning evident. However, strongly localised patterns in species composition were also evident.
The first Gallieniellidae from Eastern Africa
The Gallieniellidae is a small spider family created by Legendre (1967) for a genus (Gallieniella) of remarkable Araneomorphae with spectacularly porrect chelicerae, described by Millot (1947) from Madagascar. For quite some time the family was considered to be endemic to the large island even after the revision of Platnick (1984) who added a second genus (Legendrena) and some species from an island in the neighborhood but belonging to the same zoogeographical area. However, Platnick (1990) expanded the family, mainly on the base of the morphology of the spinnerets and included Drassodella Hewitt from the Cape region in South Africa. At the same occasion a fourth genus was announced from Australia, which drastically changed the initial endemic status of the family. Recently Goloboff (2000) described another new genus of the family from Argentina. During recent field work in forest remnants of the Taita Hills in Kenya, at the far northern edge of Eastern Arc Mountains, two species of gnaphosoid spiders were collected. They obviously lack the typical enlarged piriform gland spigots of the Gnaphosidae. The ALS have a sclerotized distal ring instead and are slightly conical and closely set. In these specimens the chelicerae are slightly porrect, at least in males and the habitus is very similar to that of Drassodella although they apparently represent a new genus. This combination of characters clearly shows that we are dealing with representatives of the Gallieniellidae, a find greatly expanding the range of the family on the African continent. The genus is diagnosed by the presence of a posterior tegular extension in the male palp but mainly by blind tubes and double spermathecae in the epigyne.
UV reflectivity of spiders and their webs
To determine the reflectivity of spider webs and spiders under UV light, spiders and their webs were photographed under normal (white) light and under UV light. It was generally found that orb‑webs (including the stabilimenta) reflect UV light about as much as they reflect white light. The spiders themselves differed in their visibility under UV light. Some spiders (e.g. Cyclosa conica, Argiope bruennichi, Zosis geniculatus) seem to reflect UV light and white light similarly, whereas other species (e.g. Araneus diadematus, Arachnura sp.) appear darker under UV light compared to white light. Only few of the species I could examine (e.g. Nephila sp.) were found to show distinct patterns under UV light which were not visible under white light.