Use the table below to jump
to abstracts, alphabetized by first author
A, B and C
Influence of Spider Silk on Microhabitat Preferences in Tarantulas (Grammastola aureostriata) |
Authors |
Institution |
| Yumiko Akamine |
Department of Biology
Eastern Michigan University
Ypsilanti, MI USA
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| Cara Shillington |
Abstract: Microhabitat selection by spiders may involve a number of parameters including optimization of foraging success and microclimate. We observed microhabitat preferences of juvenile tarantulas (Grammastola aureostriata) based on the presence/absence of spider silk. In separate trials using a Y-maze, tarantulas were given a choice of (1) conspecific web versus no web and, (2) web from a different spider species (Araneae: Agelenidae) versus no web. Activity and behaviors were video-taped for twelve hours to determine how many times spiders entered the web versus no-web sides of the y-maze and the amount of time spent on each side. Although individuals demonstrated a high degree of variation in their choices, tarantulas preferred the web-side, regardless of the origin of the web. In addition, tarantulas were more active in their first trials than in the second trials suggesting a degree of familiarization with the testing apparatus. (posted June 2, 2006)
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Watching your friends get eaten: bystander effects on predator recognition and subsequent survival in the wolf spider Pardosa milvina |
Authors |
Institution |
| Ahmed A. Alkhateeb |
Department of Biology, Susquehanna University
Selinsgrove, Pennsylvania USA
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| Mark C. Prokopovits |
| Matthew H. Persons |
Abstract: Observational learning by witnessing predation may be important for predator recognition and subsequent survival yet studies of this phenomenon among arthropods are lacking. We manipulated prior predator experiences of the wolf spider, Pardosa milvina, and then placed the spiders in open arenas with the larger co-occurring predatory wolf spider, Trochosa ruricola, to test for experience-based differences in defensive behavior and survival. We set up five experience treatments (N = 140): 1) Pardosa that observed a conspecific for 1 h, 2) Pardosa that observed the predator, Trochosa ruricola for 1 h, 3) Pardosa that observed the predator Trochosa consume a Pardosa during a 1 h period, 4) Pardosa that observed a conspecific evade predation by Trochosa for 1 h., and 5) Pardosa in an empty container. We then placed individual Pardosa in 20 cm d. arenas with a live Trochosa for 1 h and recorded predation latency, time spent moving, the number of lunges by the predator and the number of evasive hops by Pardosa. We found a significant difference in the rate of evasive hops but no significant difference in time spent moving in the arena or the number or rate of lunge responses by Trochosa across treatments; We also found significantly higher predation and shorter predation latency for the control treatment and Pardosa that witnessed Trochosa consume a conspecific relative to all other treatments. Our results suggest that prior predator experiences can influence subsequent survival of Pardosa and that witnessing predation of conspecifics can significantly increase predation risk. (posted May 25, 2006)
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Phylogeny of the spider family Tetragnathidae (Araneae) based on molecular and morphological data |
Authors |
Institutions |
| Fernando Alvarez-Padilla |
Department of Biological Sciences, George Washington University
Washington, District of Columbia USA
|
| Gustavo Hormiga |
| Gonzalo Giribet |
Department of Organismic & Evolutionary Biology and
Museum of Comparative Zoology
Harvard University
Cambridge, Massachusetts USA |
Abstract: The phylogenetic relationships and taxonomic limits of Tetragnathidae have been subject of considerable debate for more than a century. Traditionally, tetragnathid spiders have been assigned to three groups usually ranked as the subfamilies: Tetragnathinae, Nephilinae and Metinae. Current phylogenetic analyses based on morphology and behavior concluded that Tetragnathidae included the subfamily Tetragnathinae plus a paraphyletic Metinae; however, they differ in the placement of Nephilinae as sister to the remaining tetragnathids or as sister to other araneoid clades. Furthermore, a recent molecular analysis suggested that nephilines could be sister to araneids, but the taxon sample of this study was insufficient to thoroughly test this hypothesis. Our study aims to test the monophyly of Tetragnathidae, represented by a large and diverse taxonomic sample, using molecular and morphological data. We also explore the phylogenetic relationships of tetragnathids with emphasis on the "metines" problem and investigate the phylogenetic placement of nephilines. We sequenced nuclear and mitochondria genes (18S, 28S, 12S, 16S, CO1 and H3) for 26 tetragnathid taxa (including nephilines), and 18 orbicularian species as outgroups plus Nicodamus (Nicodamidae) as the root (total 45 taxa). The sequence data were aligned with dynamic and static homology criteria and analyzed with parsimony, likelihood, and Bayesian methods for phylogenetic reconstruction. We also combined the molecular data with the morphological and behavioral characters in a total evidence analysis. (posted May 25, 2006)
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Visual cues used by jumping spiders in prey identification |
Authors |
Institution |
| Julie V. Bednarski |
Neuroscience and Behavior Program
Mount Holyoke College,South Hadley, MA USA
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| Elizabeth M. Jakob |
Department of Psychology
University of Massachusetts, Amherst, MA USA |
Abstract: Most jumping spiders are generalist predators that must rapidly identify a potential prey item and attack it before it escapes. We used video techniques to examine the visual cues Phidippusprinceps uses to identify a stimulus as prey. Using a V-maze, we gave spiders a simultaneous choice between live crickets vs. live video feed of the same crickets and found no significant preference, suggesting that P. princeps interprets video images as reasonable approximations of real images. However, spiders responded differently to videos created by different methods, even though these stimuli were indistinguishable to our eyes. When given a choice between identical video clips run in Quicktime directly from a computer or burned onto a DVD, spiders chose the DVD format significantly more often. We also examined stimulus motion. Crickets, like many prey insects, move intermittently with frequent pauses. Spiders were equally likely to choose videos of crickets moving normally vs. the same clips with pauses removed, suggesting that intermittent locomotion may not be important for prey identification. These techniques hold promise for understanding visual perception in salticids. (posted May 25, 2006)
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A morphological perspective of assembling the spider tree of life |
Authors |
Institution |
| Suresh P. Benjamin |
The George Washington University
Department of Biological Sciences
Washington DC USA
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| Gustavo Hormiga |
Abstract: Assembling the Tree of Life (ATOL-spiders) aims to provide a phylogenetic framework for the study of spider evolution. The goal is to use morphological and molecular data to generate a robust phylogenetic hypothesis of the interrelationships of all spider families. This project is undertaken by an international team of 19 investigators from 14 institutions. However, putting together a large cladistic matrix of around 1,500 morphological characters from ca. 500 taxa has never been attempted before and presents many challenges. Working at this scale transforms some of the routine standard operations of systematic research because no single investigator can easily tackle empirical comparisons that involve hundreds of taxa or hundreds of characters. We will present a selection of the preliminary morphological data collected by us so far to discuss some of the issues and challenges of this component of the project.
(posted May 24, 2006)
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Loxosceles alagoni, a new species from Ixtapa Zihuatanejo, Guerrero State, Mexico (Araneae, Siicaridae) |
Authors |
Institutions |
Pablo Berea |
Octolab
Jalapa, Ver., MÉXICO
|
Greta Binford |
Department of Biology
Lewis & Clark College
Portland, Oregon, USA |
Judith Estevez |
Instituto Bioclon S.A. de C.V.
Mexico, D.F., MÉXICO |
Abstract: Loxosceles (Siicaridae) species diversity is of interest for understanding their diversification history and because their venoms are medically important. In the most recent revision of North American Loxosceles Gertsch and Ennik (1983) cataloged ~50 species with 39 described in Mexico. In the last 4 years, Instituto Bioclon, has been developing an antivenom for Loxosceles spider bites. The goal is for this antivenom to be effective for treatments of bites of all members of this genus. To facilitate this work Octolab, arachnid venom provider of Instituto Bioclon, has extensively collected Loxosceles with an effort to fully understand species diversity in Mexico. In the process of this work we have found at least two populations that are sufficiently distinct from described taxa to warrant new species status. Here we describe one of these based on examination of 15 adult males and 15 adult females from Guerrero State in Southwestern México. We propose the name Loxosceles alagoni after Dr. Alejandro Alagon, a researcher of Mexican Loxosceles. This species is most similar Loxosceles boneti and Loxosceles colima (Gertsch,1958). These three species are big and dark with a star or triangle pattern on the dorsal carapace. The Loxosceles alagoni epygyna receptacles have a simple large lobe projecting forward, while receptacles of Loxosceles colima present small extensions at the top of the lobe and receptacles of Loxosceles boneti present a curved lobe attached near middle. The male palpi of all three taxa have a curved embolus with a broad region in the middle. (posted June 5, 2006)
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Unraveling the mechanical properties of composite silk threads spun by cribellate orb-weaving spiders |
Authors |
Institutions |
| Todd A. Blackledge |
Department of Biology, University of Akron
Akron, Ohio USA
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| Cheryl Y. Hayashi |
Department of Biology, University of California at Riverside
Riverside, California USA |
Abstract: Orb web weaving spiders depend upon the mechanical performance of capture threads to absorb the energy of flying insect prey. Most modern orb-weavers spin wet capture threads with core fibers of flagelliform silk. These threads are extremely compliant and extensible due to the folding of their constituent proteins into molecular nanosprings and hydration by a surrounding coating of aqueous glue. Yet, phylogenetic evidence demonstrates that cribellate capture threads predate the use of viscid capture threads in orb webs. Cribellate capture threads are composite structures consisting of core fibers of pseudoflagelliform silk surrounded by a matrix of fine dry cribellar fibrils. To better characterize how pseudoflagelliform and cribellar fibrils function, I investigated the mechanical performance of cribellate capture threads for three genera of spiders (Deinopis, Hyptiotes, and Uloborus) that spin very diverse web architectures. Pseudoflagelliform core fibers were stiffer and stronger, but also much less extensible, than flagelliform silk. However, cribellate capture threads achieved overall high extensibilities because the surrounding cribellar fibrils contributed substantially to the tensile performance of threads long after the core pseudoflagelliform fibers ruptured. In the case of Deinopis capture threads, up to 90% of the total work performed could be attributed to these fibrils. These findings yield insight into the evolutionary transition from cribellate to viscid capture threads. (posted May 15, 2006)
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Scorpion locomotion regulation by light wavelengths |
Authors |
Institution |
Gregory R.C. Blass |
Department of Zoology
University of Oklahoma
Norman, Oklahoma USA
|
Doug Gaffin |
Abstract: The activity of scorpions is regulated by the photoperiod of their environment. A few hours after sunset, scorpions reach their peak level of activity. Physiological recordings indicate that scorpions have varying sensitivities to different wavelengths of light. Recent behavioral studies in choice chambers with half treatment light and half no light have suggested biases for different wavelengths of light. Those results did not correlate directly with reported physiological spectral sensitivity of the median and lateral eyes, which show peak sensitivity in the green and a slightly lower shoulder in the UV. In this study, we have modified our previous assay to look at the effect wavelength has on scorpion locomotion. Scorpions (Centruroides vittatus) were confined to small circular arenas containing a smaller circular barrier in each arena's center. The scorpions were presented with one of four light treatments (infrared, red, green, and ultraviolet) all of the same intensity. Every animal experienced all four light treatments, each lasting 30 minutes and separated by fifteen minutes of no light. While light treatments did not significantly affect the level of locomotion (P > 0.01), the order of treatments was significant (P< 0.01), and an overall decrease of locomotion was observed during all treatments. We are currently developing a refined behavioral assay to reduce scorpion light adaptation and behavioral variability to determine if consistent differences exist in scorpion locomotion under different wavelengths of light. (received May 17, 2006)
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Energetic investment and reinforcement of the function of different components of the cobwebs of black widows in relation to physiological status |
Authors |
Institution |
| Cecilia Boutry |
Department of Biology, University of Akron
Akron, Ohio USA |
| Todd Blackledge |
Abstract: Webs are usually considered as a way for spiders to capture prey; however, webs could also function as anti-predator devices, particularly for three-dimensional webs which surround spiders with barriers of silk. Previous studies in our lab have shown that black widows (Latrodectus hesperus) modify their web architecture as a function of their hunger state. In particular, hungry spiders emphasize components of the web involved in prey capture while sated spiders emphasize features that are likely to increase the defensive value of the web. However, black widows could also modify the thread diameters between the different components. This variation may either reinforce the function of certain parts of the web or compensate for energy invested in the different parts. We measure the thread diameters of the three components of the cobweb (sticky gumfooted threads, sheet and support threads) in spiders fed varying numbers of crickets for one week. We also weigh each part of the web to estimate energetic investment by the spiders and gain insight into the spiders' priorities. Sticky gumfooted threads and sheet threads function directly in prey capture; therefore, starved spiders should give these structures high priority by investing relatively greater mass of silk in them. Support threads could be used physically to stop predators such as wasps; and this could be made more effective by increasing thread diameters. In general, we expect fed spiders to give priority to protection against predators by allocating relatively more silk to support threads than do starved spiders. (posted May 17, 2006)
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Rediscovery of Tapinocyba emertoni after 62 years |
Author |
Institution |
| Richard A. Bradley |
Department of Evolution, Ecology and Organismal Biology
Ohio State University at Marion, Marion, Ohio USA
|
Abstract: The species Tapinocyba emertoni Barrows and Ivie, 1942 was described by William Barrows and Wilton Ivie based on two male specimens collected on 23 March, 1928. I am aware of no additional records that have been published for this species since the original description. During curation of the Ohio State University's spider collection I discovered four additional specimens, one male and three females (undescribed). These were collected at Cantwell Cliffs, Ohio on 06 November, 1938 by William Barrows. There is a label in Barrow's handwriting that indicates that these are "paratypes". I do not know why Barrows did not include these additional specimens, particularly the only known females in the original description. All of the specimens were collected by "litter sifting". In an attempt to re-locate specimens of this species, I have collected 19 1m2 litter samples from four localities in the Hocking Hills vicinity. These small samples, only 146 specimens, contained a rich diversity of spiders with representatives of 47 species. Among the samples were three additional males and eight additional females of T. emertoni, all from Cantwell Cliffs State Park, bringing the total number of specimens for the species to 17 (6 males and 11 females). These data are too sparse for any definitive conclusions, but it appears that T. emertoni is locally endemic in deep litter of the Hocking Hills region. (posted May 25, 2006)
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Constellation array: a new sensory structure in scorpions (Arachnida: Scorpiones) |
Authors |
Institutions |
Michael S. Brewer |
Department of Biological Sciences, Marshall University
Huntington, West Virginia, USA
|
Victor Fet |
Michael E. Soleglad |
Borrego Springs, California, USA |
David P. A. Neff |
Department of Chemistry, Marshall University
Huntington, West Virginia, USA |
Abstract: A peculiar constellation-shaped microscopic array of several chemosensory sensilla is described for the first time in scorpions. This sensillar array is located on the external aspect of the distal portion of the fixed finger of pedipalp. We present data on the constellation array across four parvorders, six superfamilies, 12 families, 23 genera, and 28 species of extant (orthostern) scorpions. The constellation array was observed in all scorpion taxa. Observed number of sensilla in the constellation array varied from one (Vejovoidus) to 15 (Calchas), on average 6 ± 3; the size of the sensillum is 5-10 micrometers, their shape varying from conical to hair-like. The sensilla are socketed, and appearance of their "button-like" socket areola differs from other mechanosensory and chemosensory setae common on the scorpion's body and appendages. As observed in Calchas nordmanni (Iuridae) and Euscorpius tergestinus (Euscorpiidae), there was no difference in number of sensilla between juveniles and adults. The constellation array size (maximal distance between two sensilla) usually varied between 100 to 300 micrometers, with Buthidae arrays markedly smaller in size. There was no apparent correlation between the size of a species and constellation array size. This ultrastructural character can be potentially of diagnostic use in scorpion systematics at family and genus levels. We suggest that the constellation array could be a contact chemosensory organ. (posted April 17, 2006)
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Leg autotomy affects both terrestrial and aquatic locomotion in the wolf spider Pardosa valens |
Authors |
Institutions |
| Christopher A. Brown |
Department of Biology, Tennessee Tech University
Cookeville, Tennessee USA
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| Daniel R. Formanowicz, Jr. |
Department of Biology, University of Texas at Arlington
Arlington, Texas USA |
| C. Christopher Amaya |
Biology Department, Siena College
Loudonville, New York USA |
Abstract: Many spiders voluntarily amputate (autotomize) a leg as an antipredator behavior. While beneficial in the short term (as it can allow the spider to survive encountering a predator), leg autotomy may have detrimental effects over the longer term. In several species of wolf spiders, leg autotomy causes a reduction in burst sprint speed, an important trait both for avoiding predators and capturing food. In this study we examined burst sprint speed before and after leg autotomy in males and females of the riparian-zone wolf spider Pardosa valens. Since this species moves readily both on land and the water surface, we conducted experiments in linear race tracks mimicking both these surfaces. In terrestrial trials, males and females did not differ in speed, but both sexes ran significantly slower following loss of a leg. In aquatic trials, females ran significantly faster than males, and leg loss led to a significant decrease in speed for males but not females. We also found a potential temperature effect, as spiders run in the evening (when they were presumably warmer) were generally faster than those run during the morning. Despite females weighing nearly twice as much as males, all of the above results held when adjusting for body mass. Finally, males were more likely not to run on the aquatic track than were females, and to go shorter distances when they did run. These results suggest that both aquatic and terrestrial locomotion are impaired by leg loss in P. valens, and these costs may differ between sexes. (posted May 23, 2006)
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Effects of experimental harvesting on boreal forest spider assemblages: a cross-Canada comparison |
Authors |
Institutions |
| Christopher M. Buddle |
Department of Natural Resource Sciences
McGill University
Ste Anne de Bellevue, Québec, CANADA |
| David P. Shorthouse |
Department of Biological Sciences
University of Alberta
Edmonton, Alberta, CANADA |
Abstract: Two large-scale forestry experiments, in eastern and western Canada (Québec and Alberta, respectively), were established in the late 1990s to test the effects of alternative silvicultural strategies on biodiversity in northern boreal mixed-wood forests. We collected spiders in pitfall traps several years after various partial cutting treatments were established in each experiment. Our objective was to compare the effects of partial cutting on spider assemblages (diversity and community composition), and to assess whether effects were similar in projects located over 3000 km apart. Overall, 98 species (6107 individuals) were collected from Alberta and 86 species (3414 individuals) were collected from Québec. Of these 44 species were common to both regions. Ordination analysis and indicator species analysis revealed a distinct regional effect, as the composition of the fauna from the boreal plains ecoregion of Alberta was distinct from the fauna of the boreal shield (Québec). However, the effects of partial cutting were similar in each project, and the removal of between 25 and 33% of the trees shifted the fauna from one typical of old-growth conditions to an assemblage approaching what was found in clear-cut sites. Clear-cutting also resulted in the homogenization of the spider assemblages. Indicator species analysis revealed the same wolf spider species dominated the clear-cuts in both projects. The old-growth forests contained a fauna that was easily disrupted by moderate partial cutting, and thus conservation of the spider fauna in northern forests subjected to harvesting will require retention of old-growth forests. (posted May 17, 2006)
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Activity cycles and vertical stratification of spiders in cornfields |
Authors |
Institution |
| Alan B. Cady |
Department of Zoology, Miami University
Oxford, Ohio USA
|
| Ryan B. Homsher |
Abstract: Spider distribution and abundance across the diel period has been investigated in various row crops but is not well-studied in corn. It is unknown whether certain families or groups of spiders prefer specific locations on corn plants, or if spiders change position over the diel period or across the season. Thus, a nine-week observational study of spiders on and around corn plants in six one-half hectare conventionally-tilled corn fields was conducted to determine daily spider activity cycles, their positions on the plants, and the composition of spider assemblages. Most variability of spider numbers and their community compositions appeared to be related to their phenology and corn growth stages. There was a well-defined stratification of spider families on the corn plants. The Lycosidae dominated the ground layer while the Salticidae were most prevalent on the plant tops throughout the season. Other spider families occupying the plants shifted their location during the summer. Web-building spiders (Theridiidae, Tetragnathidae) were sensitive to changing corn plant structure as the growing season progressed. Salticid and thomisid numbers on the plants were inversely related. There was evidence for interactions among foliage-running spider families, but they seemed not to impact web-building spiders. Most spider activity was at night. Lycosids and linyphiids contributed most to a mid-day activity spike early in the season. Salticids and theridiids added to this peak later on. No significant effects on spider numbers from the presence of straw refugia were found, but more lycosids tended to be near corn plants associated with refugia. (posted May 25, 2006, revised June 1, 2006)
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Molecular phylogeny and biogeography of Loxosceles and Sicarius (Araneae: Sicariidae): Gondwanan vicariance? |
Authors |
Institution |
| Melissa Callahan |
Department of Biology
Lewis & Clark College
Portland, Oregon USA
|
| Melissa Bodner |
| Greta Binford |
Abstract: Loxosceles and Sicarius spiders are notorious for their ability to cause dermonecrotic lesions in mammalian tissue. Species in both genera are native to Africa, Central and South America, and Loxosceles are also native to North America, the West Indies, Mediterranean Europe and China. We used a molecular phylogenetic approach to uncover the continental-level relationships within this lineage in order to 1. understand what factors have lead to diversification of the lineage, and 2. to gain a framework for understanding evolution of venom in this group. The age of this lineage is not known; however their present day distribution suggests that they were present on Western Gondwana (Africa & South America) before the continents split. We analyzed phylogenetic relationships among representatives from each of these continents using the nuclear marker, 28s, and the mitochondrial markers, ND1/16s. Tree topologies consistently support that divergences largely correspond with the break-up of Gondwana. With current taxon sampling we uncovered two distinct clades of Loxosceles in Southern Africa that are paraphyletic with respect to New World species. These results suggest that Loxosceles and Sicarius diverged long before Africa and South America split and Loxosceles began to diversify before the split. (posted May 26, 2006)
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Responses of Geolycosa wolf spiders to fire and flood in Florida scrub |
Author |
Institution |
| James E. Carrel |
Biological Sciences, University of Missouri-Columbia
Columbia, Missouri, USA
|
Abstract: Two species of rare burrowing wolf spiders, Geolycosa xera archboldi and G. hubbelli, co-occur in xeric, fire-maintained scrub only on the Lake Wales Ridge in south-central Florida. This ancient, sandy ecosystem is a globally important center of endemism threatened by rapid development. Annually for 20 years (1987-2006) I conducted censuses of both spiders in 15 permanent plots, each 10 x 10 m, to determine whether the Geolycosa species, like many native plants and vertebrates, benefit from periodic burning of scrub. Previous studies show most spiders (80-90%) survive fires because they are protected in their burrows, several cm beneath the soil surface. Densities of both Geolycosa rose significantly within a year after two wildfires (May 1989 and February 2001), but thereafter their numbers declined because gaps of open sand quickly disappeared as the scrubby matrix resprouted and leaf litter accumulated. However, the rate of decline in spider densities after the 2001 wildfire was precipitous. A post-hoc analysis showed that chronic flooding caused by above-normal precipitation for 5 years in a row starting in summer of 2001, which was augmented by hurricane events, resulted in decimation of Geolycosa populations in many plots. The last time such flooding occurred was at least 55 years ago. Hence, burrowing wolf spiders seem to be adapted to frequent fires but not infrequent floods. (posted May 16, 2006)
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Environmental influences on silk age and how it affects courtship behavior of the wolf spider Schizocosa ocreata |
Authors |
Institutions |
David L. Clark |
Dept. of Biology, Alma College
Alma, Michigan USA |
J. Andrew Roberts |
Department of EEOB
The Ohio State University Newark
Newark, Ohio USA |
George W. Uetz |
Dept. of Biology, University of Cincinnati
Cincinnati, Ohio USA
|
Alyssa Farley |
Dept. of Biology, Alma College
Alma, Michigan USA |
Abstract: The adult female wolf spider (Schizocosa ocreata) releases a dragline of silk when walking which is known to possess pheromones. These chemicals induce various courtship behaviors from the male spider when he is exposed to the silk. This study examined two things; 1) How the length of time males spent on courtship behaviors was influenced by various ages of silk; and 2) Whether or not the silk being aged in the field under natural conditions or in a controlled laboratory environment made a difference on the length of time spent on courtship behaviors. For silk aged outdoors, results show a decrease in the number and duration of behaviors from time #1 (0-2 hour old silk) and times #2-5 (2-4 hours old, 4-6 hours old, and 6-8 hours old, and 24 hours old) with time #5 inducing a minimal amount of courtship behaviors for a short period of time. For data collected for silk aged indoors, there does not appear to be a decrease in male response across time periods. Taken together, these results imply that the signals from the female pheromones are weakened with age when exposed to natural environmental conditions. (posted April 28, 2006)
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Growth rates in three species of tarantula: Lasiodora parahybana, Eupalaestrus Campestratus and Grammostola aureostriata |
Authors |
Institution |
| Laurie Cummins |
Department of Biology
Eastern Michigan University
Ypsilanti, Michigan USA
|
| Cara Shillington |
Abstract: Tarantulas, while long feared by humans, have only recently become the subject of scientific investigations. Consequently, many aspects of their life history are not well understood. The purpose of this study was to compare the average growth rates for three species of tarantula (Araneae: Theraphosidae): Lasiodora parahybana, Eupalaestrus campestratus and Grammostola aureostriata.
We hypothesized that the growth trends for the three species would differ based on life history patterns. Because of the differences in life history and morphology between males and females, we hypothesized that the measured exoskeletons of all species would also exhibit a distinct sexual dimorphism.
Growth rates were based on the increase in size between successive molts. Using the exuvia from all individuals for each species, carapace length and width, femur length and tibia length were measured. The average number of days between molts was also determined. Current analyses suggest that sexual dimorphism exists in all three species. In addition, initial findings also indicate that G. aureostriata has the fastest growth rate while E. campestratus has the slowest growth rate, supporting the proposed hypotheses. (posted May 26, 2006)
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Structure of papillae on the pedipalps of solifugae (Arachnida, Solifugae) |
Authors |
Institutions |
| Paula E. Cushing |
Denver Museum of Nature & Science
Department of Zoology
Denver, Colorado USA
|
| Jack O. Brookhart |
| Lorenzo Prendini |
American Museum of Natural History
Division of Invertebrate Zoology
New York, New York USA |
| Gary W. Mierau |
The Children’s Hospital
Department of Pathology
Denver, Colorado USA |
| Luann Goin |
| Hans Kleebe |
Colorado School of Mines
Golden, Colorado USA |
| Peter Payne |
Criterion Laboratories
Vancouver, British Columbia, CANADA |
Abstract: Some male solifugids in the families Eremobatidae, Karshiidae and Solifugidae (Arachnida, Solifugae) have clusters of conical to hairlike projections on the ventral surface of the metatarsus of the palpal papillae. The function of these structures is unknown. We examined the ultrastructure and microstructure of the papillae found on representatives of the three families using Scanning Electron Microscopy (SEM), histological techniques and Transmission Electron Microscopy (TEM). We found similarities in the ultrastructure of papillae among genera within a family and distinct family-level differences in ultrastructure. Structures evident from the histological examination suggest that the papillae are chemoreceptors. Behavioral observations suggest that the papillae may be used as contact chemoreceptors during copulation when the male solifugid grasps and maintains contact with the female's body using the pedipalps. (posted May 24, 2006)
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Colorado spider survey update |
Authors |
Institution |
| Paula E. Cushing |
Denver Museum of Nature & Science
Department of Zoology
Denver, CO USA
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| Jozef Slowik |
Abstract: The Colorado Spider Survey (CSS) began in May 1999. This project was modeled after the Ohio Spider Survey. The objectives of the CSS were to gather baseline information about the biodiversity of spiders throughout Colorado and the Rocky Mountains/Great Plains ecoregion and to involve citizen scientists in this biotic survey. In the seven years of the CSS, 670 people have attended training workshops or classes. Of these, 137, or 20%, have remained actively involved past the initial training activity, 11 have joined the American Arachnological Society, four have presented papers at AAS meetings, one has had a paper accepted in the Journal of Arachnology, and three others are currently working on a research project. Six CSS participants have given lectures about spiders to school groups, park personnel, or members of the general public. CSS participants have helped build the DMNS arachnology collection from less than 50 vials in 1998 to over 22,250 vials today representing 645 species in 44 families. Data from the survey is regularly published online at http://www.dmns.org/spiders/default.aspx and at http://canadianarachnology.dyndns.org/data/canada_spiders/. (posted May 24, 2006)
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The identity of the small synanthropic Pholcus (Pholcidae) in the northeastern quadrant of the United States |
Author |
Institution |
| Bruce Cutler |
Microscopy & Analytical Imaging Laboratory
and Department of Ecology & Evolutionary Biology
University of Kansas, Lawrence, Kansas USA
|
Abstract: Pholcus manueli Gertsch, originally described from New Jersey, has been found in six other states. It is a small, widespread, synanthropic species found both inside and outside buildings and manmade structures. It has been frequently misidentified as P.opilionoides Schrank a widespread synanthropic European species. However, P. opilionoides has yet to be found in North America. Diagnostic characters that separate the two species are shown which can easily be seen with a 10X triplet hand lens. Male P. manueli have a slender and straighter palpal procursus than males of P. opilionoides in which the procursus is broad and distinctly elbowed. Female P. manueli have the sides of the epigynum deeply scalloped, female P. opilionoides have the sides of the epigynum shallowly excavated. The other synanthropic Pholcus in the region, P. phalangiodes (Fuesslin), is much larger with a much longer leg span. Both P. manueli and P. phalangiodes may be found together at the same site. (posted May 16, 2006)
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D, E and F
Phylogenetic systematics of the spider genus Cyrtognatha (Araneae, Tetragnathidae) |
Authors |
Institution |
| Dimitar Dimitrov |
Department of Biological Sciences
George Washington University
Washington, D.C., USA
|
Gustavo Hormiga |
Abstract: We present the results of an ongoing research project on the taxonomy and phylogenetics of the araneoid genera Agriognatha O.-P. Cambridge and Cyrtognatha Keyserling (Tetragnathidae). All members of this lineage of tetragnathine spiders live in the Neotropical region where they are often found in tropical cloud forests. We document for the first time the web architecture of some of the members of this group. Agriognatha is a junior synonym of the Cyrtognatha. The results of our monographic work suggest that Cyrtognatha includes 23 species; eleven of them are new to science. A cladistic analysis of more than 120 morphological and behavioral characters scored for 22 species of Cyrtognatha and a diverse array of tetragnathid and araneoid taxa has provided robust support for the monophyly of the genus and for its placement within the subfamily Tetragnathinae. We will discuss some of the synapomorphies of Cyrtognatha, including the very unusual female genitalia in which the spermathecae have been greatly reduced and the sperm storage function has shifted to a specialized sac. (posted May 23, 2006)
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Evidence that evolutionarily convergent spine microstructure facilitates sand adhesion in the cryptic spider genera Sicarius (Sicariidae) and Homalonychus (Homalonychidae) |
Authors |
Institution |
| Rebecca P. Duncan |
Department of Biology, Lewis & Clark College
Portland, Oregon USA
|
| Greta J. Binford |
Abstract: Spiders from the unrelated genera Sicarius (Sicariidae) and Homalonychus (Homalonychidae) live in deserts and cover their bodies in sand, which is likely a form of camouflage. Sand adhesion correlates with the densely distributed spines found in both genera and Levi and Levi (1969) briefly noted that in Sicarius, sand particles adhered to the feathery protrusions of spines in the spinneret region. To determine the importance of spines and their morphology in sand adhesion, we (1) conducted hair removal experiments to test the necessity of spines in sand adhesion in Sicarius; (2) used scanning electron microscopy to observe interactions between particles and spines; (3) compared spine microstructure of Sicarius to related taxa that do not adhere sand; and (4) compared spine microstructure of Sicarius to that of Homalonychus. In Sicarius, a significant increase was observed in the number of particles that adhered to the cuticle when spines were present. Particles associated strongly with regions of the Sicarius cuticle that contained spines and adhered directly to long, thin hairlettes that protruded anteriorly and laterally along the proximal distal axis of spines. The lack of hairlettes in genera related to Sicarius suggests that hairlettes originated in the ancestors of this genus coincidently with the origin of sand adhesion. Interestingly, Homalonychus also possessed hairlettes anteriorly and laterally on spines. This convergent feature suggests that hairlettes play a key role in sand adhesion and that they may be an adaptation to confer crypsis. (posted May 26, 2006)
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Review of the described species of Metacyrba (Araneae: Salticidae) |
Author |
Institution |
| G. B. Edwards |
Florida State Collection of Arthropods
FDACS, Division of Plant Industry
Gainesville, FL USA
|
Abstract: Parkella Chickering 1946 = Metacyrba F. O. P.-Cambridge 1901, n. syn.; Parkella venusta Chickering 1946 = Metacyrba venusta (Chickering 1946), n. comb.; Parkella fusca Chickering 1946 and Dendryphantes franganilloi Caporiacco 1955 = Metacyrba venusta (Chickering 1946), n. syn. The six valid described species of Metacyrba [floridana Gertsch 1934, insularis (Banks 1902), pictipes Banks 1903, punctata (Peckham & Peckham 1894), taeniola (Hentz 1846), venusta] are diagnosed and re-illustrated to show previously unrecognized genitalic differences. Metacyrba similis Banks 1904 is resurrected as a subspecies, becoming Metacyrba taeniola similis Banks 1904, n. status. The female of Metacyrba pictipes Banks 1903 is described for the first time. Metacyrba arizonensis Barnes 1958 = Platycryptus arizonensis (Barnes 1958), n. comb., and Marpissa magna (Peckham & Peckham 1894) = Platycryptus magnus (Peckham & Peckham 1894), n. comb. Platycryptus broadwayi (Peckham & Peckham 1894) = Platycryptus magnus (Peckham & Peckham 1894), n. syn. Metacyrba nigrosecta (Mello-Leitão 1945) = Balmaceda nigrosecta Mello-Leitão 1945, comb. restored. The genera Balmaceda Peckham & Peckham 1894, Metacyrba, and Platycryptus Hill 1979 are compared morphologically among themselves and to Breda Peckham & Peckham 1894 and Fuentes Peckham & Peckham 1894. The distributions of Balmaceda picta Peckham & Peckham 1894 and Metacyrba species are updated. Metacyrba punctata is newly introduced into Florida. Marpissa melanura F.O.P.-Cambridge 1901 is resurrected; it is not a synonym of Marpissa minor F.O.P.-Cambridge 1901 nor of Platycryptus californicus (Peckham & Peckham 1888). (posted May 16, 2006)
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Assessing predation risk in Schizocosa wolf spiders: Environment matters more than sex, speed or ornamentation |
Authors |
Institution |
| Kasey D. Fowler-Finn |
School of Biological Sciences
University of Nebraska-Lincoln
Lincoln, NE USA
|
| Eileen A. Hebets |
Abstract: While benefits of elaborate secondary sexual traits can frequently be realized by assessing male mating success, costs of production or maintenance are often more elusive. Elegant laboratory studies using video playback previously suggested that male foreleg ornamentation and active courtship in some Schizocosa wolf spiders increases visual detection, thus increasing predation risk and representing a cost of ornamentation. Under more natural conditions however, predation risk is likely influenced by many factors including, but not limited to, conspicuousness against the background and locomotory performance. Here, using artificial enclosures in the field, we compare actual predation rates of two naturally co-occurring Schizocosa male forms (brush-legged and non-ornamented) and females. Prior to release in the field, individual locomotory performance (i.e. speed) was determined in the laboratory. Enclosures were set up on each of two field substrates (rocks and leaf litter) and predation rates were recorded during the day and night using a co-occurring Hogna species as the predator. Predation rates were highest at night with more predation occurring on rocks than leaf litter. Predation rates did not differ among any groups (brush-legged males vs. non-ornamented males vs. females) on either substrate. Locomotory performance also did not differ among groups and individuals escaping predation were not significantly faster than those suffering predation. Our results suggest that while secondary sexual traits may increase visual detection and thus predation risk in a simple environment, other environmental factors such as microhabitat and time of day may be more important in determining predation risk under natural conditions. (posted May 31, 2006)
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G, H and I
Does A1 +A2 = B in scorpion peg sensilla? |
Author |
Institution |
| Douglas D. Gaffin |
University of Oklahoma, Department of Zoology,
Norman, Oklahoma, USA
|
Abstract: Peg sensilla on scorpion pectines appear to have a dense plexus of synaptic interactions between primary chemosensory afferents. These unusual interactions may be important to the information processing power of these mid-ventral organs as the animal samples ground-based chemical information. However, there is some question as to whether the previously reported inhibitory 'B' unit is actually distinct from the A1 and A2 units or if it is an electrical coupling of A1 and A2. I looked closely at the B waveform to see if it is derivable from the A1 and A2 waveforms. In addition, I examined waveforms where two or more units fired in close temporal proximity. Several of these waveforms classified to type B with A1 or A2 type waveforms clearly within the refractory periods of their waveforms. Furthermore the number of these B/A1 or B/A2 doublets was in line with the number predicted based on the firing frequency of the B, A1, and A2 units in the peg. As such, this analysis corroborates the original conclusion that the B unit is an event separate from A1 and A2 and that it has an inhibitory influence on the behavior of A1 and A2 in scorpion peg sensilla. (posted May 16, 2006)
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The effects of spider cues on Colorado potato beetle (Leptinotarsa decemlineata) foraging behavior |
Authors |
Institution |
| Jeffrey J. Garofalo |
Department of Biology, Susquehanna University
Selinsgrove, Pennsylvania USA
|
| Steven R. Heverley |
| Matthew H. Persons |
Abstract: Colorado potato beetles, Leptinotarsa decemlineata, are chemically-protected crop pests on economically important solanaceous plants. We measured predation on potato beetles by two species of wolf spider, Hogna helluo and Pardosa milvina. We found no predation on beetles by either species of spider during a 4 h test period (n = 24/spider species). We also measured leaf damage by beetles on eggplants, Solanum melongena, in the presence of Hogna and Pardosa. We found significant reductions in herbivory in the presence of Hogna but not the smaller Pardosa (n = 24/spider species). In another experiment, we measured leaf preference or avoidance for leaves previously walked on by one of four spider species for 24 h (Tetragnatha laboriosa, Misumenoides formipes, Hogna helluo, or Pardosa milvina). When given a simultaneous choice between eggplant leaves with spider cues and those without, beetles showed a significant initial avoidance for leaves previously occupied by Hogna, but beetles showed no significant initial avoidance of spider-cued leaves of any of the other three spider species (n = 48/spider species). In the absence of live spiders, beetles showed significantly lower herbivory levels on leaves previously occupied by Hogna, Pardosa, or Tetragnatha, compared to leaves without spider cues, but beetles showed no reduction in herbivory on leaves previously occupied by Misumenoides. Our results suggest that even chemically-protected herbivores show reduced feeding in the presence of some generalist predators and that chemical cues from predators (silk and excreta) may also reduce herbivory even when these predators present no predation risk. (posted May 25, 2006)
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The influence of substrata on seismic signals of the wolf spider Schizocosa ocreata (Araneae: Lycosidae) |
Authors |
Institutions |
| Jeremy S. Gibson |
University of Cincinnati
Department of Biological Sciences
Cincinnati, OH USA
|
| J. Andrew Roberts |
Department of Evolution, Ecology, and Organismal Biology
The Ohio State University Newark
Newark, OH USA |
| George W. Uetz |
University of Cincinnati
Department of Biological Sciences
Cincinnati, OH USA |
Abstract: Courtship displays of male Schizocosa ocreata (Hentz) are multimodal, consisting of visual and seismic signals. Previous research has shown that variation in seismic signals is condition-dependent and influences mating success. Although isolated male seismic signals are sufficient to elicit female receptivity, it is possible that other (environmental) factors might affect signal transmission and perception in the field. In our current research, we are testing the effects of substratum type on seismic signals by recording adult male spiders in the lab and field on different substrata.
We used a Polytec LDV-100 laser vibrometer system to record spider signals and analyzed digital files with the AviSoft sound analysis program. We conducted studies in the laboratory, recording male wolf spider courtship on four different substrata typical of the natural habitat of the spiders -- leaves, bark/wood, soil, and rock. We also conducted studies in the field using maple leaves. Female wolf spiders were placed on substrata for 24 hrs to deposit silk (with pheromones), and then removed. Males were placed on the substrate, and courtship signals were recorded for 5 minutes using the LDV.
Analysis of recordings revealed that leaves are highly conductive substrates for seismic signals in contrast to other habitat surfaces (soil, wood, rock). We also tested different species of leaves to determine whether varying degrees of leaf thickness or stiffness might affect transmission of seismic vibrations, and found no differences. Additional studies will investigate changes in power spectra of seismic signals as a function of distance, leaf structure and composition. (posted May 26, 2006)
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Diagnostic DNA barcoding of spiders: utility, variability, and choice of sequence |
Authors |
Institution |
| Matthew H. Greenstone |
U.S.D.A. – Agricultural Research Service Insect Biocontrol Laboratory
Beltsville, Maryland USA
|
| Daniel L. Rowley |
Abstract: Barcoding is the use of a DNA sequence to identify an organism to species. Since all life stages share the same DNA, it should be particularly useful for identifying immature individuals. This is a critical need for spider ecological research, where the majority of animals collected in a field study are apt to be immatures and hence difficult or impossible to assign to species. A group calling itself the Barcode of Life Initiative has proposed using mitochondrial cytochrome oxidase I (CO I) as a universal barcoding sequence for all animal species. Among its virtues for this task are multiple copy number, which will make PCR assays to detect them sensitive; rapid rates of evolution, which ought to enable distinguishing recently diverged species; and a catalog of universal primers that simplifies "fishing" them out of previously uncharacterized genomes. In published research on species in the genera Cheiracanthium, Frontinella, Grammonota, Hibana, Pardosa, and Rabidosa, we and colleagues showed that CO I is indeed able to distinguish even closely related species from one another, and to assign immatures unequivocally to the correct species. Here we provide the first data on spider CO I haplotype variability. We also suggest why other sequences might be more appropriate for spider DNA barcoding than CO I. (posted May 12, 2006)
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Male-male aggression in a wolf spider (Pardosa milvina) |
Authors |
Institutions |
| Gayatri Guhanarayan |
Department of Zoology, Miami University
Oxford, Ohio USA
|
| Chad D. Hoefler |
| Ann L. Rypstra |
| Matthew H. Persons |
Department of Biology, Susquehanna University
Selinsgrove, Pennsylvania USA |
Abstract: The evolution of fighting behavior has been extensively studied for several decades with a strong focus on male-male competition for resources. Since fighting is costly, it is to an animal's advantage to assess its mate correctly before engaging in such interactions. In this study, we specifically address how female mating status and condition affect the frequency of aggressive male behavior in male-male contests. The wolf spider Pardosa milvina is abundant in the fields, are easy to rear in the lab and have conspicuous aggressive behaviors. In our study with Pardosas, we looked at male-male competition in the presence of a female. The males used for this experiment were subjected to a uniform diet regime and were all field caught. The females were randomly distributed into four groups: non-virgin well fed, non-virgin food limited, virgin well fed and virgin food limited. The competitive interactions between the two males in presence of each of these types of females were video taped and recorded as contact or non-contact forms of aggressive behavior. The data was analyzed using the contingency test and the Kruskal-Wallis test. Our results indicated that both female mating status and condition influenced the level of aggression in male-male contests. The well-fed virgin females specifically showed more instances of all types of aggressive behaviors. (posted May 31, 2006)
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Neurohaemal organ of the scorpion Heterometrus swammerdami
|
Author |
Institution |
| M. Habibulla |
Director, Human Services Fund
Schaumburg Township, Hoffman Estates, Illinois USA
|
Abstract:In Heterometrus swammerdami there are no known endocrine glands. In the brain and the subesophageal ganglion there are groups of specialized neurons. These nerve cells synthesize a variety of biologically active compounds. Some of these products can clearly be visualized with special staining methods in paraffin sections under the microscope. Since the nervous tissue is enveloped with four layers thick perineurium, a 'blood brain barrier' exists. For this reason the synthesized neurosecretory material cannot be discharged directly in to the haemocoel and must be delivered to the cephalic blood vessels. The neurosecretory product is transported through the axons and the neurofiber tract pathways, forming neurohaemal organs terminating in the blood vessels surrounding the cephalothoracic nerve mass. A variety of specialized neurons which secrete biologically active compounds will be presented and their transport through the nervous system discussed. (posted May 17, 2006)
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Tracking the role of Diptera in complex spider food-webs |
Author |
Institution |
| James D. Harwood |
Department of Entomology, University of Kentucky
Lexington KY 40546-0091 USA
|
Abstract: Generalist predators are widely acknowledged to contribute to valuable levels of biological control in agroecosystems throughout the world. Although their feeding habits can result in the rejection of target pests in favor of preferred and often more nutritious alternative prey, these predators are capable of colonizing habitats prior to the arrival of pest species. The effect of this subsistence upon alternative, non-pest species can be twofold. Whilst feeding upon such items generally enhances their fecundity thus improving population growth and levels of biological control exerted by the entire population, the presence of non-pest species during times when pest regulation is required can result in a reduced level of pest consumption per individual predator.
Until recently, the role of alternative prey in sustaining predator populations has been limited to laboratory studies and field trials examining the fecundity, feeding behavior and growth rates of species subjected to diets of varying quality. However, antibody and molecular techniques have allowed predation rates to be evaluated in the field, quantified the strengths of specific trophic linkages and identified the structure of complex food webs. The development and application of a Diptera-specific monoclonal antibody is discussed in the context of evaluating biological control by spider communities in the field. Evidence was gathered to suggest that Diptera form an important non-pest food resource early in the season, but predation on non-pest prey items when pests arrive potentially disrupts biological control. (posted April 17, 2006)
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Female mate choice varies with female quality |
Authors |
Institutions |
| Eileen A. Hebets |
School of Biological Sciences, University of Nebraska
Lincoln, NE USA |
| Stephanie Reed |
University of California - Berkeley
Berkeley, CA USA |
| Jennifer Wesson |
Abstract: Until recently, most studies of female choice have assumed that mating preferences are fixed within a population or species. New studies however have highlighted the importance of factors such as female age and prior experience on mate choice. Among-female variation certainly exists in natural populations and one way in which females may vary relates to quality. For example, prior research on Schizocosa ocreata has demonstrated that juvenile feeding regimes influence adult body size and body condition. Here, using spiders collected from a mixed population of S. ocreata/rovneri and raised in the laboratory on two different diets that varied in both quality and quantity (low/high nutrient), we tested whether adult female mate choice varies with female quality (i.e. juvenile diet treatment). First, consistent with previous work, we found that high nutrient spiders matured more quickly than low nutrient spiders and were significantly larger as adults. Males also matured earlier than females. Upon maturation, females from both high and low nutrient groups were paired simultaneously with a low and high nutrient male. We found no obvious differences in courtship effort between the males, however we did find female mate choice to be dependent on diet treatment as high nutrient females mated more frequently with high nutrient versus low nutrient males while low nutrient females showed no mating preference. These results further support the notion that female mate choice is not fixed and suggest that experiments using well-fed laboratory subjects could potentially provide an artificially enhanced picture of the strength of female choice. (posted May 26, 2006)
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A tale of one species where experience matters??? |
Authors |
Institutions |
| Eileen A. Hebets |
School of Biological Sciences, University of Nebraska
Lincoln, NE USA |
| Cor Vink |
Biocontrol and Biosecurity, AgResearch
Lincoln 8152 NEW ZEALAND
|
Abstract: Classic studies using isolated populations of Schizocosa ocreata and S. rovneri have previously demonstrated these two species to be ethospecies, isolated only by courtship behavior. Recently however, we discovered a mixed population of brush-legged (nr S. ocreata) and non-ornamented (nr S. rovneri) males. In this more southern population, males of both forms overlap in time and space and both molecular as well as behavioral results suggest that the two forms are freely inter-breeding. Initially, in an attempt to distinguish between the species, we conducted exposure trials in which subadult females were randomly assigned to either a brush-legged or a non-ornamented exposure treatment. As penultimates, these females experienced courtship advances from thei | |
