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