Abstracts
Arranged Alphabetically
by First Author
2002 Annual Meeting
The American
Arachnological Society
(Most recent entry: 6 / 10 / 2002) |
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| A Phylogenetic View of Sociality in
Cobweb Spiders (Theridiidae) |
| Author: Ingi Agnarsson |
Institutions: George Washington University
and Smithsonian Institute |
|
| Abstract: Spiders are a lineage of predominantly aggressive
and distinctly territorial hermits. Tolerance is usually limited to conspecifics,
briefly during mating, or as tiny juveniles emerging from the egg sac. Yet,
a few species do share webs, and about 20 do so permanently (quasi-sociality).
While about half of these are phylogenetically widespread and isolated,
the remainder are cobweb spiders. As the family represents less than 6%
of spider diversity, the concentration of social species there seems to
require an explanation. In order to examine the phylogenetic patterns of
sociality within the family I present a cladistic reconstruction of theridiid
relationships, based on morphological data. The results indicate that; first,
the relatively high number of social theridiids is a result of multiple
(four) origins of sociality, rather than a diversification within a single
social lineage. Thus, as in other spiders, social clades never are specious;
spider sociality seems to represent a diversification dead end, rather than
a key innovation. Second, I found that within Theridiidae, social origins
are non-randomly clustered within a distal lineage. Presumably that lineage
exhibits traits that facilitate social evolution. The "maternal care
route" hypothesis, suggests that web-sharing sociality is merely an
extension of maternal care, whose prolongation may be more likely where
certain other traits, e.g. three- dimensional webs are present. Congruent
with such ideas, I found that sociality in cobweb spiders is indeed concentrated
in a lineage where maternal care occurs in the presence of three-dimensional
webs. (Added 5 / 28 / 2002) |
| Spiders in elementary schools |
| Author: Bill Bennett |
Institution: Crosbyton County Memorial Museum,
TX |
|
| Abstract: Scream and squash is the usual reaction of
kids, a behavior learned from parents, when encountering a spider. That
is until they have been properly enlightened by a biologically hip teacher
(rare and endangered) or a by a courageous AAS volunteer. These knee-biters
learn to distinguish between all the good species from the few really dangerous
ones. They also learn what distinguishes the arachnids from other arthropods,
their varied predatory techniques and their important place in the environment.
Halloween offers a great opportunity for spider education as well as Native
American studies, e. g., legends of the Spider Grandmother in Kiowa lore,
Spider Woman of the Cherokees, etc. You will find that 1st through 4th graders
are easier to teach than graduate students! (Added 6 / 1 / 2002) |
| The evolutionary origin of sphingomyelinase
D in Loxosceles venoms: how, when and why? |
| Author: Greta Binford |
Institution: University of Arizona |
|
| Abstract: Sphingomyelinase D (SMD) in Loxosceles
venoms is a sufficient causative agent for lesion formation and is only
known elsewhere in a few species of pathogenic bacteria. This makes the
evolution of SMD an interesting puzzle. I will discuss insights into the
evolution of Loxosceles SMD based on characteristics of the gene
and comparative biochemical assays. The gene spans at least 6,500 bp, contains
5 introns, and is a member of a multigene family. A signal sequence indicates
SMD is expressed as a zymogen with a trypsin cleavage activation site. Weak
amino acid sequence similarity suggests SMD is a divergent member of the
broadly conserved glycerophosphoryl diester phosphodiesterase family (GDPD).
These data strongly suggest that spider SMD has been evolving within a eukaryotic
genome for a long time ruling out evolutionary origin by recent horizontal
transfer from bacteria. Comparative enzyme assays indicate that SMD originated
in the ancestors of Loxosceles and Sicarius making it likely
that the enzyme is present in all members of this clade. Venoms of spiders
in the Loxosceles/Sicarius clade (with SMD) are more potent when
injected into Manduca sexta than are venoms of Drymusa, a
close relative without SMD in their venom. This is suggestive that the enzymatic
activity of SMD (present in large quantities in the venom) may contribute
to prey paralysis. (Added 5 / 16 / 2002) |
| Behavioral diversification in the
adaptive radiation of Hawaiian orb-weaving Tetragnatha |
| Authors: Todd Blackledge and Rosemary Gillespie |
Institution: University of California, Berkeley |
|
| Abstract: The extreme isolation and habitat heterogeneity
of the Hawaiian Islands has contributed to many spectacular evolutionary
radiations of organisms, exemplified within spiders by the orb-weaving Tetragnatha
(Araneae: Tetragnathidae). While the "spiny leg" lineage of Tetragnatha
has abandoned the use of webs in prey capture, most endemic Tetragnatha
(approximately 50 species) still construct orb webs. This web-building clade
may have speciated across the archipelago more rapidly than the spiny leg
clade, suggesting that construction of webs has facilitated species coexistence
or even diversification itself by allowing finer subdivision of microhabitat
or prey resources within habitats. Here, I show that sympatric species of
Hawaiian Tetragnatha display distinct differences in the microhabitats
and architectures of their webs, as well as the prey that they capture.
I examine the possibility that web architecture and location reflect adaptation
to local selective pressures and that similarities in selective pressures
between habitats on different islands have led to convergent evolution of
community structure. (Added 5 / 7 / 2002) |
| Neotropical jumping spiders of the genera
Sidusa and Cobanus, with discussion of phylogenetic relationships
within the Euophryinae (Araneae: Salticidae) |
| Author: Gitanjali S. Bodner |
Institution: University of Arizona |
|
| Abstract: Members of the jumping spider genera Cobanus
F. O. Pickard-Cambridge 1901 and Sidusa Peckham and Peckham 1896
are amongst the most abundant and conspicuous spiders in many Neotropical
rainforests, yet distinguishing features have not been proposed for either
genus, and neither has previously been revised. Similarly, the euophryine
subfamily is one of the dominant salticid groups throughout the world, yet
very little work has been done on its boundaries and internal phylogenetic
structure. This work suggests synapomorphies for Cobanus and Sidusa,
and addition of newly discovered species approximately doubles the size
of both genera. Twenty-four species are newly described here, twelve re-described,
three synonymized, two transferred to other genera, and several recognized
as being misplaced. Phylogenetic analysis of morphological characters in
these species and representatives of thirty other euophryine genera supports
the sister relationship and mutual monophyly of Cobanus and Sidusa,
provides insight into character variation within the subfamily Euophryinae,
and suggests the existence of several previously unrecognized euophryine
clades. (Added 6 / 4 / 2002) |
| Identification of Chitin in the Extracellular
Matrix of the Duct Region of the Ampullate Glands of Latrodectus hesperus |
Authors: Teresa Bonomini, Jason Newmark,
Laurie ONeil and Merri Lynn Casem |
Institution: California State University,
Fullerton |
|
| Abstract: The purpose of this study was to examine the
structure and composition of the major and minor ampullate glands in the
Black Widow Spider (Latrodectus hesperus); specifically, the duct
region. We hypothesized that the duct did not contain chitin. The presence
of chitin was determined using calcofluor, a chitin-specific dye. Findings
were not consistent with our hypothesis; fluorescent microscopy revealed
the presence of chitin in the duct region of 80% of the specimens analyzed.
(Added 5 / 16 / 2002) |
| Title: Molecular comparisons of scorpion species groups from the Genus
Vaejovis (Family Vaejovidae) using a 500 base-pair sequence of mitochondrial
16S rDNA |
| Authors: Karen Bost, Richard Henson, Mary
Connell, and Zack Murrell |
Institution:Appalachian State University |
|
| Abstract: The genus Vaejovis has the largest
distribution and degree of variation of any scorpion genus found in the
United States. Due to a lack of distinct morphological characteristics,
the phylogeny of this genus is poorly understood. Species of this genus
have been separated into five loosely defined groups based on morphological
and ecological characteristics. The five species groups include eusthenura,
intrepidus, mexicanus, nitidulus, and punctipalpi.
Representative species and populations from each group except intrepidus
were examined using a 500 base-pair sequence of mitochondrial 16S rDNA in
order to assess phylogenetic relationships. The intrepidus group
was not analyzed due to the inability to obtain specimens. Scorpions were
obtained at night using ultraviolet light in Big Bend National Park and
Guadalupe Mountains National Park Texas, throughout Utah, Arizona, New Mexico,
North Carolina, Tennessee and Mexico. Habitats ranged from consolidated
sand to rocky substrate. Sequences were compared to Hadrurus arizonensis
, a member of a related Family (Iuridae). Preliminary data consisting of
twenty-eight sequences from the four representative groups and outgroup
were analyzed using PAUP where a heuristic search was performed to create
a consensus tree computed by fifty percent majority rule. Early evidence
suggests a combined monophyletic origin of the mexicanus and the
nitidulus groups. The eusthenura and punctipalpi groups
have not been resolved at this time. (Added 4 / 26 / 2002) |
| Gum-Foot Threads: Prey Capture by Spring-Action
in Black Widow Webs |
| Authors: Crystal Botham, Yurixsa López
and Anne Moore |
Institution: University of the Pacific |
|
| Abstract: Vertical gumfoot threads in a black widow's
(Latrodectus hesperus) cobweb catch ground-moving prey by sticking
to the prey, detaching from the ground and raising the prey into the air.
We propose that gumfoot threads, unlike other spider silks, act as a spring,
using stored energy from pre-stretching of the threads to pick up the prey.
We tested the ability of the gumfoot threads to store energy by cyclic loading
tests, enabling measurement of energy input and output. Our tests show that
gumfoot silk is very efficient (81%) at low strain (<2%) but not efficient
(24%) at higher strains (5-10%). Low-strain efficiency in spider silks has
not been previously measured, so silk was thought to act as a shock absorber
(energy dissipation) rather than a spring (energy storage). Our initial
observations of intact gumfoot threads in the web are consistent with this
spring hypothesis. Our stress-strain analysis shows that gumfoot silk has
nearly identical material properties as dragline silk. They both show an
initially stiff region followed by a distinct decrease in stiffness as the
silk is stretched beyond 2% of its original length. This yield point suggests
a significant change in the way that the silk molecules resist being stretched.
Therefore, the two silks can have identical properties yet exactly the opposite
function (energy storage as opposed to energy dissipation) because the spider
uses the silks at different strains. (Added 5 / 12 / 2002) |
| Envenomation by Centruroides scorpions |
| Author: Leslie Boyer |
Institution: University of Arizona |
|
| Abstract: In North America, approximately 8 species
and subspecies of Centruroides scorpion are significantly neurotoxic
to humans. Venom includes sodium channel neurotoxins that provoke a clinical
syndrome affecting nicotinic, muscarinic and neuromotor systems. Children
in particular are susceptible to neurotoxicity, of sometimes life-threatening
severity. Treatment varies widely with local medical capabilities, traditions,
and laws. Currently there is no scorpion antivenom approved for use in the
United States, but efficacy has been demonstrated both with an Arizona State
University goat immunoglobulin product and, in Mexico, with an equine F(ab)2
product. Efforts are under way to demonstrate cross-protection using the
Mexican antivenom against envenomation by the US species. (Added 5 /
17 / 2002) |
| Diurnal Use of Artificial Shelters by Harvestmen
in Experimental Gardens |
| Authors: Sarah Bradbury and Alan Cady |
Institution: Miami
University, Oxford, Ohio |
|
| Abstract: Harvestmen (Opiliones) are a Generalist Predatory
Arthropod and are usually numerous and common in gardens. Little is known
of how they may contribute to suppression of herbivore activities in such
habitats if their populations were augmented. Previous results from experimental
enclosures show that brussel sprouts plants in the presence of harvestmen
had greater growth and less damage from herbivores. These experiments were
continued with cucumbers and to test the effects of small lean-to shelters
designed to provide harvestmen with favorable microhabitats during the day
to prevent their leaving to seek shelter from daytime heat and desiccation.
Twelve 2X2 meter metal flashing enclosures holding cucumbers and brussel
sprouts were erected. Six of the 12 enclosures contained 15 harvestmen each,
uniquely marked to denote treatment. Three enclosures with and three enclosures
without harvestmen were supplied with 8 25X25 cm lean-to shelters. Each
of 4 treatments (harvestmen with shelters; harvestmen without shelters;
no harvestmen with shelters; and no harvestmen, no shelters) were replicated
three times. Harvestman positions were noted during nocturnal and diurnal
censuses and observations. Herbivore plant damage, fruit yields, and biomass
were measured. Harvestmen chose the shelters during the hotter, drier daytime,
and were found out on vegetation at night. Thus, shelters may reduce harvestman
emigration out of gardens during the day, inducing them to remain in positions
to prey upon pests or their eggs at night. Plants in the presence of harvestmen
showed trends for less damage and higher fruit yields, especially during
mid-season. (Added 5 / 16 / 2002) |
| Papillae on the Pedipalps of Solifugae:
structure and proposed function |
| Authors: Jack Brookhart and Paula Cushing |
Institution: Denver Museum of Nature &
Science |
|
| Abstract: Some male solifugids have a series of conical
structures called papillae on the ventral surface of the metatarsal segment
of their pedipalps. We present the first known images of the microstructure
of these papillae and present our hypothesis as to their function. (Added
5 / 7 / 2002) |
| Clinical Aspects of Envenomation by Black
Widow Spiders |
| Author: Sean Bush |
Institution: Loma Linda University Medical
Center |
|
| Abstract: Clinical signs and symptoms following black
widow spider envenomation may include severe muscular pain, high blood pressure,
and profuse sweating. Initially, a bite may cause sharp pain or go unnoticed.
The lesion following the bite typically has a "target" appearance,
i.e., central reddened puncture site surrounded by blanching and an outer
halo of redness. Unlike brown recluse bites, the skin around the bite site
does not rot. Pain may progress from the bite site gradually to involve
muscles in the limbs, abdomen, back, and/or chest. Abdominal pain may mimic
surgical conditions. Patients may complain of a headache and develop facial
swelling, called Latrodectus facies. Nausea and vomiting may ensue. Sweating
may be isolated to the area surrounding the bite or may be generalized.
The envenomation syndrome usually manifests within an hour, reaches maximum
intensity within 12 hours, and can last for days to weeks. There is antivenom
for black widow spider bites. However, there has been a death attributed
to an allergic reaction to this antivenom, so most U.S. doctors opt to treat
patients' symptoms with pain medications, such as morphine, and sedatives,
such as valium. Interestingly, Australian red-back spider antivenom works
for U.S. black widow spider envenomation. Calcium has been reported to be
no more effective than placebo and is no longer recommended. Although around
2,500 black widow spider bites were reported last year to the American Association
of Poison Control Centers, no deaths have ever been reported to Poison Control
since its first report in 1983. (Added 5 / 7 / 2002) |
| Spiders in Texas Pecans: Are They Affected
by Fire Ants? |
Authors:Alejandro Calixto, Allen Dean,
Allen Knutson, Marvin K. Harris
and Bill Ree |
Institution: Texas A&M University |
|
| Abstract: Imported Fire Ants (IFA) are known to interfere
with natural enemies in pecans. This ecological disruption may contribute
to pest outbreaks by preying on natural enemies. We investigated this effect
on spiders associated with the pecan agroecosystem. The study was conducted
in a pecan orchard (Robertson Co., TX). Plots treated for IFA were compared
with untreated, three treatments were established and replicated four times;
1. untreated controls; 2. chlorpyrifos (Lorsban 4E TM) as a trunk treatment
(was used as a chemical barrier to impair ants to climbing up the tree)
and; 3. broadcast methoprene (ExtinguishTM) bait treatment that reduced
IFA densities by 70%. Ground and foliage spiders were studied by using 4
pitfall traps and 200 artificial refuges per treatment weekly, monitoring
from May 2000 thru May 2002. Refuges consisted of strips of corrugated cardboard
(6x3 in) attached to the terminal twigs of the tree and inspected every
week from April 2001 thru May 2002. A total of 15,588 spiders were collected
in all, 3,372 in pitfall traps and 12,216 in corrugated strips. 127 species
distributed into 26 families were recorded during the study, 77 species
occurred in refuge strips, 94 species in pitfall traps and 44 species in
both methods. Results suggested that spider densities were not affected
by IFA directly but effect over other natural enemies may cause an increase
in numbers in control plots due to lack of high intraspecific competition.
Untreated plots tended to have more spiders compared with treated. Spiders
seem to be present year round on the tree/ground playing an important role
as a "buffer" predator over pest outbreaks. while multivoline
insect predators (lacewings and lady beetles) vary considerably in conjunction
with prey availability and often occur at very low densities. Spiders consistently
occur at reasonably stable densities. (Added 6 / 10 / 2002) |
| Geographic variation in prey capture
in a colonial orb-weaving spider |
Authors: Florencia
Fernández Campón
and
Susan E. Riechert |
Institution: University of Tennessee, Knoxville |
|
| Abstract: Prey availability affects tolerance and cooperation
in spiders. Individuals from populations from habitats with high prey availability
showing higher levels of cooperation. In addition, temporal variation in
prey availability could be affecting plasticity levels with which individuals
respond. Populations changing their behavior to adapt to local conditions
favored against populations lacking that plasticity. <Parawixia
bistriata> is a colonial spider in which cooperative capture is facultative.
By doing reciprocal transplants in habitats with different prey availability
and seasonality we evaluated the hypotheses of a) higher cooperation under
high prey levels, b) more plasticity when temporal variation in prey level
existed. In manipulative studies we observed the response towards prey of
increased size based on number of individuals participating in capture,
in communal feeding and latency of the feeding group to divide. We expected
more individuals participating in prey capture and feeding under higher
prey conditions as well as longer durations of the feeding groups, indicating
higher tolerance as well. Populations differed in their response but not
as expected. Despite the low sample size, data from transplants suggest
that dry populations present more plasticity, behaving like native populations
when trasplanted to wet habitats, whereas wet populations maintained their
behavior under different levels of prey. (Added 5 / 31 / 2002) |
| Abundance patterns, stream use and
overwintering in a community of stream-bank cursorial spiders |
| Authors:Karen Cangialosi, Sharon Martinson
and David Cook |
Institution: Keene State College |
|
| Abstract: While spiders are predominately terrestrial,
a few species are known to enter aquatic environments for most or some of
their lives. Spiders living along a stream bank may make use of the water
flow for foraging for aquatic organisms or for dispersal. The objectives
of this study were to document annual abundance patterns for the community
of stream-bank cursorial spiders and to quantify their degree of entry into
the stream drift. A drift net was placed in each of three stream sites in
forested areas in Cheshire County, New Hampshire and net contents were collected
and recorded twice a week for approximately one year. Simultaneously, pitfall
traps were placed along three, 30m transects adjacent to each stream and
contents were collected and recorded once a week. Air temperature, water
temperature, and water level were also recorded at each sampling period.
We found that most species had non-overlapping periods of peak abundance,
and that most species that were along the stream margins did not enter the
drift. However, two species of Dictynids, (Circurina) entered the
drift in large numbers in early December when the average daily temperature
reached below freezing. It it possible that these species may be using the
streams to locate suitable overwintering sites. (Added 5 / 13 / 2002) |
| Are mechanoreceptors involved in the
neural circuitry of scorpion peg sensilla? |
| Author: Steven Carter and Douglas Gaffin |
Institution: University of Oklahoma |
|
| Abstract: Scorpion pectines are paired, ventral appendages
that extend from their eleventh body segment. Each pecten resembles a comb
with a jointed spine connecting numerous teeth. The ventral surface of each
tooth contains a dense patch of truncated hairs, called peg sensilla. Morphological
and electrophysiological studies have concluded that numerous chemoreceptive
neurons are present in each peg while only one mechanoreceptor is present.
Synaptic interactions between chemosensitive cells have been identified
via cross-correlation analysis; however, the mechanoreceptor has received
very little attention, and it is unknown if it is part of the peg circuitry.
Our research focused on the general characteristics and roles of the mechanoreceptors
in peg sensilla of the desert grassland scorpion (Paruroctonus utahensis).
Extracellular electrophysiological recordings were obtained from the bases
of individual pegs during mechanical stimulation. These recordings were
then segregated into individual cellular firings using wave-form analysis,
which showed the existence of at least four different waveforms (three putative
chemoreceptors and one mechanoreceptor). Cross-correlation analysis did
not reveal signs of synaptic interaction between the mechanoreceptor and
two of the chemoreceptors while a third was inconclusive. Taken together
with previous morphological studies it appears that the chemoreceptors and
mechanoreceptors form synaptically isolated neural populations in scorpion
peg sensilla. (Added 5 / 12 / 2002) |
| Ultrastructure of the Major Ampullate
Gland of the Black Widow spider, Latrodectus hesperus |
Authors and Institutions
| Merri Lynn Casem |
California State University, Fullerton |
| LPP Tran |
Pitzer College |
| Anne M.F. Moore |
University of the Pacific |
|
|
| Abstract: Silk production in the spider occurs within
specialized glands that are capable of the synthesis of large fibrous proteins
and the post-translational processing of those proteins to form an insoluble
fiber. The major ampullate gland of Latrodectus hesperus (black widow)
is similar in morphology to those found in the Araneid spiders. The tail
domain of this gland is highly protein synthetic, giving rise to a core
protein product. The silk product is transported to the ampullar region
where it is stored. The cells of the ampulla wall produce an electron dense
material that appears to form a "skin"; surrounding the silk "core";
generated in the tail. The duct of the gland consists of at least two distinct
cell types. One type contains 'honeycomb' vesicles of unknown function while
the other possesses elaborate microvilli that may be involved in the reabsorption
of water and subsequent dehydration of the silk. The duct is reinforced
with a chitinous cuticle. As the silk product transits through these various
stages of assembly it can be seen to undergo a condensation or concentration,
possibly reflecting the influence of both the dehydration and shear forces
that occur within the duct. (Added 5 / 13 / 2002) |
| Spider Diversity of Orchid Island, Taiwan:
A Comparison Between Habitats generated from various aboriginal activities |
| Authors: Kuan-Chou Chen and I-Min Tso |
Institution: Tunghei University, Taichu, Taiwan |
|
| Abstract: Tropical forests exhibit very high spider
diversity, but due to the difficulties of conducting comprehensive sampling
in tropical areas relevant studies are quite rare. Orchid Island is a tropical
island 91 km off the southeast coast of Taiwan. The forests on this island
are the northern most tropical forests in East Asia. In this study, the
spider diversity of Orchid Island was studied and those from three types
of habitats generated by various kinds of aboriginal activities were examined.
Habitat type studied in this study included the forest interior, the meadow
outside the forest and the forest edge. All habitat types had four replicates
located in Yonsing farm, Yeying village and Chungshing farm respectively.
In each replicate four 5m X 5m sampling plots were established. In addition,
we also set up additional 8 plots in the relatively undisturbed forest in
Tienchi for comparison. Three field trips were conducted in August, 2000
and February and April, 2001. Spiders were collected by six methods (pitfall
traps, litter substraction, shrub sweeping-net, day and night hand collection
and canopy sweeping-net ) to have a comprehensive representation of diversity
from all microhabitats in the plot. From the adult specimens obtained, a
total of 110 species from 18 families were identified. Shannon-Weaver function,
Simpson index and Evenness were not significantly different among habitat
types, suggesting a similar dominance pattern island-wide. However, species
composition differed considerably among different types of habitats. Result
of a UPGMA analysis using pair-wise Euclidean distance demonstrated that
specimens from 56 plots can be divided into seven major groups, with Tienchi
plots united as a unique cluster. In addition to species composition, foraging
guild composition also differed significantly among habitat types. These
results suggest that the diversity of ground spiders in Orchid Island tropical
forest is quite heterogeneous. Spider diversiy in disturbed area did not
constitute a subset of those in the relatively undisturbed area. (Added
5 / 15 / 2002) |
| Detritus decoration built by Cyclosa
confusa may not function to improve foraging or concealing |
| Authors: I-Chia Chou and I-Min Tso |
Institution: Tunghei University, Taichu, Taiwan |
|
| Abstract: In some orb-weaving spiders, in addition to
regular components of web they also construct extra structure known as decorations
on web. Besides silk, decorations built by many species of the genus Cyclosa
are composed of debris, leaf and egg sacs. So far, there is no direct test
of the functions of these debris decorations built by Cyclosa spiders.
Although direct support is lacking, debris decorations are traditionally
believed to function as a camouflaging device. In this study, we test this
hypothesis by comparing the mortality of C. confusa with or without
detritus decorations on their webs. Besides, prey remains deposited on the
webs of the social spiders Mallos gregalis had been shown to be capable
of attracting prey insects to spider webs. Therefore in this study we also
examined if C. confusa webs decorated with prey remains intercept
more prey than undecorated ones. Two field studies were conducted in a tropical
forest in Orchid Island, Taiwan in February and April, 2002. Results from
both field trips showed that no significant difference was found in prey
interception rates between experimental group (decoration removed) and control
group (decoration remained). Similarly no significant difference was found
in mortality rates between experimental and control groups in our February
study. However, results of our April study indicated that C. confusa
with decorations suffered significantly higher mortality than those where
decorations were experimentally removed. These results suggest that detritus
decorations of C. confusa do not seem to function to increase insect
catching or to decrease mortality rate. Instead, detritus decoration may
even be a cost to C. confusa by increasing the mortality rate. Why
C. confusa consistently build decorations on their webs given the
cost of increasing mortality rate awaits future study. (Added 5 / 15
/ 2002) |
| An Inventory of the Spiders of the Great
Smoky Mountains National Park |
| Author: Frederick
Coyle |
Institution: Western Carolina University |
|
| Abstract: The key objectives of this project are to
determine what spider species live in the Great Smoky Mountains National
Park (GSMNP) and how they are distributed among the park's habitats. The
primary sampling protocol involves a team of collectors using four standardized
methods that sample spiders in most microhabitats and vegetation strata.
This protocol yields large and statistically tractable replicate data sets
that reflect the relative abundance of species in the sites and habitats
studied and will facilitate comparisons of species richness, taxonomic composition,
and guild structure among diverse communities and regions. We have collected
2010 1-hr ground, aerial, beat, and sweep samples, and 450 1 m sq. litter
samples, containing an estimated 52,000 adult spiders from 17 intensively
sampled focal sites representing 16 of the park's major habitats and from
accessory sites representing additional habitats. Eighty percent of these
adult spiders have been sorted to morphospecies, 40% have been identified,
and 20% have been entered into a Biota database. The identified spiders
comprise 482 species, 36 of which appear to be undescribed. Products of
this inventory will include a Biota database available on the internet,
a monographic guide to GSMNP spiders (in CD or DVD format), and a pocket
guide for park visitors. Published papers based on inventory data describe
the spider assemblage structure at selected sites, evaluate the effectiveness
of species richness estimators, and describe the habitat distribution patterns,
life cycles, and behaviors of species of Araneus, Tetragnatha,
Neriene, Theridion, and Pirata. (Added 5 / 14 /
2002) |
| The Effects of Altered Precipitation
on Leaf Litter Spider Communities |
| Author: Kenneth Cramer |
Institution: Monmouth College |
|
| Abstract: At Oak Ridge National Labs in Tennessee, a
long-term manipulative experiment was initiated in 1993 to study the potential
impacts of precipitation change due to global warming in a temperate deciduous
forest. The Throughfall Displacement Experiment (TDE) diverts 33% of ambient
rainfall from one 80x80m plot to another. I evaluated the impacts of the
TDE on spider abundance and species richness and composition. Samples of
leaf litter from 0.2m^2 circular plots taken in August and November from
the wet, ambient (control), and dry plots were hand sorted for spiders.
Leaf mass (as an estimate of leaf volume and habitat area) had a significant
positive correlation with spider abundance, more so of selected taxa, especially
Dictyna. Total spider bundance was unchanged across treatments, although
leaf mass was significantly greater in the dry plots. Changes in species
richness were minimal, yet rare species may have been adversely affected
by moisture changes. Species composition, however, was affected by the treatments
(as well as by slope and season), and certain species showed distinct habitat
associations correlating with treatment or slope of the experimental plots.
(Added 5 / 15 / 2002) |
| Cryptic Vicariance in Homalonychus
(Araneae, Homalonychidae) |
| Authors:Sarah Crews and Marshal Hedin |
Institution: San Diego State University |
|
| Abstract: When a vicariant event has occurred in the
past, but is not readily detectable by analysis of morphology alone (i.e.,
two or more morphological groups are not apparent), this vicariance is said
to be cryptic. Detection of cryptic vicariance is important for studies
of conservation and biodiversity, as well as for elucidating biogeographic
histories. Cryptic vicariance has been shown to occur in numerous vertebrate
taxa distributed on the Baja Peninsula, where molecular analyses reveal
deep phylogenetic splits in morphologically homogeneous taxa. Here we report
the first evidence of cryptic vicariance in Baja for an invertebrate group,
the spider family Homalonychidae. Using mtDNA data we have detected a deep
molecular split between northern and southern populations of Homalonychus
theologus on the Baja Peninsula. Roth (1984) made no mention of genitalic
variation within H. theologus, although he highlighted considerable
variation in the congeneric H. selenopoides. This north south
split may correspond to a mid-peninsular seaway that existed around 1.6
mya. (Added 5 / 13 / 2002) |
| Title: Spider Genera of North America Revision Project |
| Author: Paula Cushing |
Institution: Denver Museum of Nature &
Science |
|
| Abstract: In September 2001, a team of taxonomists and interested
arachnologists proposed to the American Arachnological Society Executive
Committee that the Spider Genera of North America guide by Vince Roth be
revised. The Spider Genera of North America Revision Team, or SGNART, consists
of Paula Cushing, Darrell Ubick, Suzanne Ubick, Don Buckle, Mike Draney,
Nadine Dupérré, Jack Kaspar, Pierre Paquin, Dave Richman,
and Barbara Roth. The SGNART proposes to have the revision completed by
the end of 2004. This poster serves both as an overview of the revision
project as well as a solicitation for assistance from interested taxonomists
who wish to assist in this revision. Taxonomists who contribute a major
revision of a particular taxonomic group will receive chapter authorship.
(Added 4 / 19 / 2002) |
| Semi-heavy Metal: Calcium, Manganese
and Zinc in the Oral Cuticle of the Tarantula, Stichoplastus sanguiniceps
(Araneae: Theraphosidae) |
| Author: Bruce Cutler |
Institution: University of Kansas |
|
| Abstract: It has been known since 1989 that some spider
sclerotized cuticle contains high concentrations of manganese (Mn) in the
tarsal claws, and zinc (Zn) in the fangs. I examined the molted exoskeleton
of Stiphoplastus sanguiniceps, a small Trinidadian tarantula for
the presence of divalent metals. The specimens were collected after molting
and frozen at -4 oC until use. Cuticle areas of interest were removed and
mounted on aluminum stubs with silver paint. After drying specimens were
sputter coated with 10 nm of gold or gold-palladium alloy. A Leo 1550 field
emission scanning electron microscope (SEM) equipped with an EDAX energy
dispersive x-ray spectroscopy system was used to provide topographical and
compositional information about the specimens. Both individual x-ray spectra
and compositional maps were taken from the different areas of the chelicerae
and fangs. As expected the fangs' surface contained significant levels of
Zn. The surface of the cheliceral teeth contained elevated levels of Mn.
Non-cheliceral tooth regions of the chelicerae did not contain elevated
levels of any metals. An unexpected finding was the presence of high levels
of calcium (Ca) in the non-surficial fang citicle. High levels of Ca are
unusual in terrestrial arthropod cuticle, except for isopods and millipedes.
Mn and Zn also occur in hymenopterous cuticle where they have been intensively
investigated. Supposedly they confer toughness on cuticle containing them,
but the mechanism for this is still unknown. Future work will examine the
distribution of these elements in oral cuticle within different spider taxa,
and look at non-molted as well as molted exoskeleton. (Added 5 / 6 /
2002) |
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D through F
| EVOLUTION OF SPERMATHECAL
STRUCTURES WITHIN THE SPIDER FAMILY TETRAGNATHIDAE |
| Author: Anne Danielson-Francois |
Institution: University
of Arizona |
|
| Abstract: The study of arachnid genitalic structures
is useful from the perspectives of systematics and sexual selection. Spider
genitalia have been used as a taxonomic tool for distinguishing between
taxa and by evolutionary biologists to test mechanisms of sexual selection
by which the variation could evolve, ranging from Fisherian run-away selection,
chase-away selection, and sperm competition. While many species have been
dissected at a gross level, few detailed studies exist that examine female
spermathecal ducts, spermathecal accessory glands and their gland pores.
Hypotheses have been proposed to explain both male behavior and the outcome
of sperm competition based on the number and location of spermathecal ducts
alone. Far less attention has been paid to the spider spermathecal gland
pores, which penetrate the cuticular wall of the spermathecae, allowing
glandular secretions to pass into the lumen of the spermathecae. The spider
family Tetragnathidae has particularly variable spermathecal morphologies,
ranging from entelegyne to haplogyne genitalic characters. Sixteen representative
members of this family and five outgroup taxa were examined with scanning
and transmission electron microscopy in order to describe the fine structure
of spermathecae, including the distribution and density of spermathecal
gland pores. The function(s) of the glandular secretion are unknown. The
distribution and density of spermathecal gland pores is discussed with regard
to possible functions of the glandular secretion. The potential influence
of spermathecal gland secretions on mating behavior and sperm competition
is discussed. (Added 5 / 14 / 2002) |
| Inventory of linyphiids from burned and
unburned oak woodland/savanna habitats in Chicago, Cook Co., Illinois |
Authors and Institutions
| Michael L. Draney |
University of Wisconsin-Green Bay |
| Petra Sierwald |
Field Museum of Natural History, Chicago |
| Nina Sandlin |
Field Museum of Natural History, Chicago |
|
|
| Abstract: Swallow Cliff is a mature remnant oak woodland/savanna
complex; Open woodlands such as these are highly endangered globally by
development and invasive vegetation. Ground spiders were sampled biweekly
during growing seasons of four years (1996-1999) at four sites using pitfall
traps as well as Berlese-extracted leaf-litter samples, flight-intercept
traps, and carrion-baited pitfall traps. This yielded 14,166 adult spiders
in 159 species and 21 families. Linyphiidae was the 2nd most abundant family
(19.0% of total adults) after Thomisidae (42.7%), but was by far the most
diverse family with 52 species (32.7%) in 22 genera; Salticidae was 2nd
with 14 species (8.9%). This includes 20 linyphiids new to Illinois, and
one species (Walckenaeria palustris) found for the first time within
the United States. The assemblage is composed of species characteristic
of both field as well as forest communities. All the species are broadly
distributed across the northern and/or eastern portions of North America
and can be considered part of the generalized Great Lakes fauna rather than
prairie biome habitat specialists. The herbaceous component of two of the
sites was experimentally burned prior to the 1999 sampling. Six of nine
abundant species (n > 30) increased or decreased their proportional representation
by over 50% during the post-burn year at the burned sites, compared with
four of eight species during the same period at the unburned sites. Thus,
although the linyphiid fauna of the burned sites changed more dynamically,
some of the observed change is apparently due to normal year-to-year variation.
(Revised 5 / 31 / 2002) |
| Title: The
Present Status and a Review of the Brown Recluse and Related Spiders, Loxosceles
spp. (Araneae: Sicariidae), in Florida. |
| Author: GB Edwards |
Institution: Florida State Collection of Arthropods,
Gainesville |
|
| Abstract: Spiders of the genus Loxosceles have
only been collected in 8 of the 67 counties in Florida. The native brown
recluse spider, L. reclusa Gertsch and Mulaik, has been found in
Alachua, Bay, Duval, Jefferson, and Leon counties, all in the northern part
of the state. The introduced Mediterranean recluse, L. rufescens
(Dufour), has been found in Orange, Osceola, and Dade counties, in the central
and southern areas of the state. All records have been interceptions of
single specimens or of established populations in one or two buildings.
There is no evidence of a widespread population of recluse spiders in Florida,
nor is there any evidence that there are frequent interactions between recluse
spiders and humans in the state. Despite hundreds of diagnoses by medical
personnel of brown recluse spider bite in Florida every year, there has
been only one instance where an alleged bite was accompanied by an actual
specimen of a brown recluse spider. Doctors should be aware of multiple
other causes of apparent pre-necrotic and necrotic wounds, and only suspect
spider bite as a last resort in regions where recluse spiders are not endemic.
(Added 5 / 3 / 2002) |
| Litter and ground surface dwelling
spiders of mixed mesophytic forests in southeast Louisiana |
| Author: Joyce Fassbender |
Institution: Louisiana State University |
|
| Abstract: Mixed mesophytic hardwood forests are composed
predominantly of magnolia, holly, and beech with a mixture of other tree
species, such as oak and hickory, and a distinct understory. Remnants of
mixed mesophytic hardwood forests in the southern United States are important
refugia for disjunct and habitat-restricted species. In Louisiana, mixed
mesophytic forest habitat is found mostly in West Feliciana Parish. I chose
two sites to conduct a study of spider diversity in litter habitats of disturbed
and mature mixed mesophytic forests. Berlese sampling was used to collect
10-kg samples of forest litter twice monthly from both sites. Collections
were made from October 1998 to October 1999. I collected 1725 adult specimens
representing 89 species in 14 families. At the mature forest site (Tunica
Hills WMA) I collected 909 adult specimens, 58 species in 12 families. At
the disturbed forest site (Feliciana Preserve) I collected 816 adult specimens,
73 species in 12 families. Species accumulation and richness estimators
indicated the likelihood that additional species were present but not collected
during the sampling period. The disturbed site had significantly greater
species diversity and more uncommon species, perhaps because of a wider
variety of microhabitats and presence of tourist and colonizer species.
The mature forest site was less diverse, perhaps as a result of more stable
and homogeneous habitat. Multiple disjunct species with northern affinities
were found. Additionally, twelve species that had not been previously reported
in Louisiana were discovered. (Added 5 / 15 / 2002) |
| Title: New data on "Euscorpius carpathicus" species complex
(Scorpiones: Euscorpiidae) from Italy, Malta, and Greece: evidence from
mitochondrial DNA and morphology |
Authors: Victor Fet (1),
Michael E. Soleglad (2),
Benjamin Gantenbein (3),
Valerio Vignoli (4),
Nicola
Salomone (4),
Elizabeth V. Fet
(1) and
Patrick J. Schembri (5) |
Institutions: (1) Department of Biological Sciences,
Marshall University, Huntington, WV 25755-2510, USA
(2)
P.O. Box 250, Borrego Springs, CA 92004, USA
(3) Institute
of Cell, Animal and Population Biology, Ashworth Laboratories, The University
of Edinburgh, Edinburgh EH9 3JT, Scotland
(4) Department
of Evolutionary Biology, University of Siena, 53100, Siena, Italy
(5) Department of Biology, University of Malta, Msida, MSD 06, Malta.
|
|
| Abstract: The first mitochondrial DNA phylogeny (based
on 16 unique haplotypes) is presented for a number of scorpion populations
from Italy, Malta, and Greece, previously classified under a "catch-all"
name of Euscorpius carpathicus (L., 1767) (Fet & Sissom, 2000).
The comparative analysis of mitochondrial gene for 16S (large subunit) ribosomal
RNA suggests that at least two clearly separated lineages are present. However,
neither of these belongs to E. carpathicus (L.) in strict sense (which
is limited to Romania; Fet & Soleglad, 2002). The first, "western"
lineage, found in northern and central Italy (also present in southern France,
Slovenia, Croatia, and Austria) is identified as E. tergestinus (C.L.
Koch, 1837) according to Fet & Soleglad (2002). Here, we identify another
monophyletic, "southern" lineage as E. sicanus (C.L. Koch,
1837), originally described from Sicily; it includes as new synonyms the
following seven subspecies: E. carpathicus canestrinii (Fanzago,
1872) and six subspecies described by Caporiacco (1950): E. c. calabriae,
E. c. ilvanus, E. c. garganicus, E. c. argentarii,
E. c. palmarolae, and E.c. linosae. Morphology also confirms
the existence of two lineages; of those E. sicanus is characterized
by unique trichobothrial pattern and number where series eb (and
in some populations, also series eba) have 5 trichobothria (instead
of always 4 in E. tergestinus). The E. sicanus lineage is
found in southern Italy (with Sicily and Sardinia), Malta, northern Africa
(Tunisia, Libya), Madeira, and southern Greece. The enigmatic "E.
mesotrichus" (Kinzelbach, 1975) from Greece (Thessaly) belongs
to this species. (Added 3 / 21 / 2002) |
|
| Sexual selection favors large body
size during opportunistic mating in male Argiope aurantia |
Authors and Institutions
| Matthias Foellmer |
Concordia University |
| Daphne Fairbairn |
UC Riverside |
|
|
| Abstract: During their quest to maximize fertilization
success, male Argiope aurantia may face a cannibalistic attack by
the female. However, males are protandrous and are often observed cohabiting
with penultimate females, with usually more than one male present per web.
While the female undergoes her molt to maturity males try to copulate with
the then defenseless female, which is known as opportunistic mating. Here,
we investigate the fitness consequences for males resulting from the ensuing
competitive interactions among them. In order to estimate male mating success
we caged those males that were found with penultimate females close to molt
with their respective females. We measured male prosoma width and patella-tibia
length of the first leg pair. Pedipalps of males were checked for signs
of insertion before and after caging, and we performed three scan samples
per day. A trial was over once the female had molted. Both prosoma width
and leg length were positively and significantly associated with mating
success, but not independent of each other. This suggests a general pattern
of selection for large size, and this was independent of number of males
present per female. Further, position of a male at the last scan before
the female's molt was an important predictor of mating success, but this
was unrelated to male size. We put these findings into context by evaluating
the relative occurrence of opportunistic mating and conclude that selection
for large male size is important in this species, despite the fact that
males are much smaller than females. (Added 5 / 15 / 2002) |
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G through I
| Polynesian Voyagers: Phylogenetic relationships
among Hawaiian Crab Spiders (Araneae: Thomisidae) |
| Authors: Jessica Garb and Rosemary Gillespie |
Institution: University of California, Berkeley |
|
| Abstract: Spiders of the family Thomisidae are characterized
as ambush predators that employ color mimicry of plants to capture prey.
The twenty described species of Hawaiian thomisids exhibit a diversity of
plant host affiliations and host-specific cryptic coloration. This diversity
led previous systematists to place the Hawaiian species into several different
genera, suggesting that they descended from several independent colonization
events to the archipelago. Recently, all Hawaiian species were hypothesized
to comprise a monophyletic group having undergone dramatic morphological
diversification subsequent to colonization. This hypothesis is tested with
a phylogenetic analysis of molecular sequence data. Specifically, a 525
bp region of the nuclear gene elongation factor 1-a
, containing two exons separated by a 168 bp intron, was sequenced
from Hawaiian representatives as well as closely related taxa from North
and South America, Africa, and several islands of French Polynesia. We compare
the resulting phylogenetic hypothesis with another generated from previously
collected mitochondrial sequence data, and determine the combinability of
the two data sets for a total evidence analysis. The resulting hypothesis
is used to assess levels of speciation following initial colonization and
whether specific colorations exhibited among the species have repeatedly
evolved. (Added 5 / 15 / 2002) |
| Spiders on the Storm: Adaptive Radiation
on Pacific Archipelagos |
| Author: Rosemary Gillespie |
Institution: University of California, Berkeley |
|
| Abstract: Adaptive radiation involves the diversification
of species to exploit different ecological roles, with related adaptations.
It is associated with the occupation of new environments that are sufficiently
isolated as to allow colonists to diversify by filling multiple ecological
roles. How is the diversification achieved? I have been studying spiders
in the genus Tetragnatha in order to elucidate commonalities underlying
patterns of adaptive radiation. In this talk I will first compare three
archipelagoes of differing isolation across the Pacific and show that the
genus has diversified within each, although the lineages are unrelated to
each other. Second, I compare different lineages within the Hawaiian Islands,
where the diversification is the most prolific, to determine how species
differentiation is occurring within the archipelago. I show that one clade,
the spiny-leg clade, has progressed down the island chain, with species
on any one island most closely related to others on the same island. Moreover,
the same set of ecological forms has evolved repeatedly, filling the ecological
space in a similar manner and allowing multiple species to co-occur. However,
another clade of spiders, a web-building clade, is ecologically conservative,
and has differentiated between geographic areas only, with a single representative
of the clade at any one site. The general conclusion is that adaptive radiation
has occurred in multiple lineages of Tetragnatha in the Pacific,
and has done so independently, with multiple mechanisms underlying diversification.
(Added 4 / 26 / 2002) |
| The systematics of spiders of the Hadrotarsus-group
(Araneae, Theridiidae) |
| Author: Mark Harvey |
Institution: Western Australia Museum, Perth
W.A. Australia |
|
| Abstract: The Hadrotarsidae were once considered amongst
the rarest and least known of all spider families and, accordingly, have
been thought to represent relatives of the Theridiidae, Oonopidae and Tetrablemmidae,
amongst others. The discovery that hadrotarsids were simply a highly autapomorphic
sub-group of the Theridiidae (Wunderlich, 1978, Forster, Platnick and Coddington
1990) and were placed with genera such as Euryopis, Dipoena,
Anatea and Yoroa in an expanded Hadrotarsinae. A revision
of those hadrotarsine spiders with reniform posterior median eyes
the Hadrotarsus-group has revealed five genera and 27 species
(22 of which are new) from Australia and southern New Guinea. The bulk of
the diversity lies within just two genera, Hadrotarsus and Gmogala,
which contain 12 and 11 species respectively. Three new genera are recognised,
two of which appear to retain at least one plesiomorphic feature, the accessory
spermathecae found in other members of the Hadrotarsinae such as Euryopis
and Dipoena. A comprehensive examination of the phylogenetic relationships
within the Hadrotarsus-group supports the monophyly of each of the
five genera, and provides some structuring within Hadrotarsus but
not within Gmogala. Many hadrotarsine species are found to possess
wide distributions that are consistent with dispersal mechanisms such as
ballooning. Most species are found in the drier woodand regions of Australia,
with very few found in rainforests, suggesting a radiation during the late
Tertiary following the onset of arid climatic patterns across Australia
during the Miocene. (Added 4 / 29 / 2002) |
| Evolution of Adhesive Mechanisms in
Cribellar Spider Prey Capture Thread: Evidence for Van der Waals and Hygroscopic
Forces |
| Authors: Anya Hawthorn and Brent Opell |
Institution: Virginia Tech |
|
| Abstract: Sticky prey capture threads are produced by
many members of the spider infraorder Araneomorphae. Cribellar threads are
plesiomorphic for this clade, and viscous threads are apomorphic. The outer
surface of cribellar thread is formed of thousands of fine, looped fibrils.
Basal araneomorphs produce non-noded cribellar fibrils, whereas more derived
members produce noded fibrils. Cribellar fibrils snag and hold rough surfaces,
but other forces are required to explain their adherence to smooth surfaces.
Threads of Hypochilus pococki (Hypochilidae) formed of non-noded
fibrils held to a smooth plastic surface with the same force under low and
high humidities. In contrast, threads of Hyptiotes cavatus and Uloborus
glomosus (Uloboridae) formed of noded fibrils held with greater force
to the same surface at intermediate and high humidities. This supports the
hypothesis that van der Waals forces allow non-noded cribellar fibrils to
adhere to smooth surfaces, whereas noded fibrils, owing to the hydrophilic
properties of their nodes, add hygroscopic forces at intermediate and high
humidities. Mathematical models of these forces are consistent with the
observed stickiness of cribellar thread. Thus, there appear to have been
two major events in the evolution of adhesive mechanisms in spider prey
capture thread: the addition of hydrophilic nodes to the fibrils of cribellar
threads and the replacement of cribellar fibrils by viscous material and
glycoprotein glue. (Added 5 / 15 / 2002) |
| Genealogical Exclusivity in Geographically
Proximate Populations of Hypochilus thorelli Marx (Araneae, Hypochilidae)
on the Cumberland Plateau of North America |
| Author:Marshal Hedin and Dustin Wood |
Institution: San Diego State University |
|
| Abstract: The issue of sampling sufficiency is too infrequently
explored in phylogeographical analysis, despite both theoretical work and
analytical methods that stress the importance of sampling effort. Regarding
the evolutionary pattern of reciprocal monophyly, both the probability of
recovering this pattern, and the possible inferences derived from this pattern,
are highly contingent upon the density and geographic scale of sampling.
Here we present an empirical example that relates directly to this issue.
We analyze genetic structure in the southern Appalachian spider species
Hypochilus thorelli, using an average sample of five mtDNA sequences
per location for 19 locations. All sampled sites are reciprocally monophyletic
for mtDNA variation, even when separated by geographic distances as little
as five kilometers. For populations separated by greater geographic distances
of 20-50 kilometers, mtDNA sequences are not only exclusive, but are also
highly divergent (uncorrected p-distances exceeding five percent).
Although these extreme genealogical patterns are most seemingly consistent
with a complete isolation model, both a coalescent method (Slatkin 1989)
and nested cladistic analysis (Templeton et al. 1995) suggest that other
restricted, but non-zero, gene flow models may also apply. Hypochilus
thorelli appears to have maintained morphological cohesion despite this
limited female-based gene flow, suggesting a pattern of stasis similar to
that observed at higher taxonomic levels in Hypochilus. (Added
5 / 12 / 2002) |
| Use of a micro-engineered chemical delivery
device to evaluate scorpion peg sensillum response to organic stimulants |
| Authors: Mujahid Hines and Douglas Gaffin |
Institution: University of Oklahoma |
|
| Abstract: Scorpions are nocturnal animals with a rich
array of finely tuned sensory structures. In particular, mid-ventral appendages
called pectines are complex chemosensory organs that are used in the detection
of food and mates. Previous electrophysiological studies have shown that
the sensory elements on pectines (thousands of minute peg-shaped sensilla)
are sensitive to a variety of volatile organic compounds. However, the stimulus
delivery mechanism used in these studies was imprecise, making it difficult
to compare response patterns among peg sensilla. We have engineered a new
device to allow chemical stimulants to be more precisely delivered to a
small group of pegs. We tested the efficacy of the engineered device and
its dynamics by designing a series of stimulations using 1-hexanol and mineral
oil as the control chemical. Peg sensilla on the pectines of Paruroctonus
utahensis and Paruroctonus mesaensis were recorded extracellularly
while being stimulated to record the elicited response pattern. We have
completed preliminary testing of the delivery device, including optimal
duration of stimulus pulse and the best size for the nozzle bore. This device
will be used to investigate a basic question of pectine functionality: do
all peg sensilla respond with the same pattern of neural activity or are
there distinct inter-peg differences? The latter would suggest a segmentation
of chemical information at the level of the peg, similar to the olfactory
epithelium of mammals. (Added 5 / 12 / 2002) |
| Sosippus,
revisited |
| Authors: Maggie Hodge and Sam Marshall |
Institution: Hiram College |
|
| Abstract: The vast majority lycosids are vagrant hunters,
either lying in wait for prey or wandering in search of prey. A few species
are sedentary, building more-or-less permanent burrows from which they ambush
passing prey. Only species in the subfamily Hippasinae build webs. These
spiders are thought to possess the most primitive morphological features
of the Lycosidae, indicating that they may represent an ancestral lineage.
The genus Sosippus builds prey capture webs that exhibit a remarkable
resemblance to the funnel-webs of agelenids. The geographic distribution
of the 10 described Sosippus species ranges from the southern United
States, through Mexico and Central America to Costa Rica. One species, Sosippus
placidus, has a very restricted distribution, having been collected
primarily at Archbold Biological Station (ABS) and from a few scrub remnants
near Lake Placid, Florida. Sosippus floridanus is sympatric with
S. placidus, but is distributed across the entire Florida peninsula.
We compared the habitat use of these sympatric species at ABS and found
that the widespread S. floridanus uses disturbed habitats such as
pastures and roadsides, while S. placidus is associated with vegetation
specific to scrub. We also describe extended maternal care in which offspring
remain in the mother's web past their first molt and feed communally off
of prey captured by the mother. This subsocial behavior was observed in
S. floridanus, S. placidus, and S. janus. (Added
5 / 17 / 2002) |
| Basin and Bajada Grassland Spider Communities
and the Invasive Grass Eragrostis lehmanniana Nees (Poaceae) |
| Author: David Hu and David Richman |
Institution: New Mexico State University |
|
| Abstract: Spider grassland communities are diverse and
play an important arthropod predator role. Recent invasion by the African
grass Lehmann lovegrass (Eragrostis lehmanniana Nees) in the Jornada
Basin has influenced the grasslands, by displacing and out-competing the
native grasses, such as threeawn (spidergrass) (Aristida spp.), mesa
dropseed (Sporobolus brevifolius) and in particular black grama (Bouteloua
eriopoda). In this study, we compared two different grassland spider
communities (basin and bajada) in which Eragrostis lehmanniana has
established and is increasing in dominance. Three Eragrostis lehmanniana
treatment levels were selected in each grassland, one of complete dominance,
an intermediate level and one of minimal influence. Spiders were collected
in hand capture visual surveys and pitfall traps with vegetation associations
noted. There were no significant differences found in spider numbers or
diversities between Eragrostis lehmanniana treatment levels. The
bajada grassland yielded a higher diversity and number of spiders than the
basin grassland. There were no significant differences in spider numbers
between sample seasons, but a higher diversity of genera was found in the
spring samples. Comparisons between levels of Eragrostis lehmanniana
influence as well as between grasslands may provide new insight into spider
community dynamics and may reveal some of the underlying associations between
desert spiders and desert grass species. (Added 4 / 19 / 2002) |
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J through L
| Field observations of the relationships
between ecological variables and orb web decorations |
Authors: Michael Justice, Vanessa Lollett
and Brandi Causey |
Institution: Nova Southeastern University |
|
| Abstract: Many species of orb weaver add conspicuous
tufts or bands of silk to their webs. Despite a fair amount of theory and
some recent testing, the ecological functions of these decorations remain
largely debatable. It is likely that the functions vary considerably across
individuals, species, and ecological circumstances. With this in mind, a
multivariate correlational approach was taken in an attempt to discern which
ecological and behavioral variables may be worthy of further study. Field
measurements were taken on adult female Argiope aurantia, Argiope
florida, Argiope argentata, Gasteracantha cancriformis,
and Nephila clavipes. The size of the spider was measured, along
with its responsiveness to a 100-Hz tuning fork applied to the web. Web
size, height, compass orientation, and angle off vertical were measured,
along with the number of Argyrodes, conspecific males, and wrapped
prey items present. In Argiope, web decorations were measured by
quantifying the geometry of the stabilimentum; specifically, stabilimenta
were measured by counting the number of arms, the length of each arm, the
angle between arms, and the number of interradial silk crossings. In Gasteracantha,
the number of silk tufts was counted and whether they were on radii or frame
threads was noted. Many of these variables have never been quantified in
the field, so the results provide some baseline natural history data for
these species. The relationships between web characteristics and ecological
factors provide some limited support for a visual signaling role of these
decorations. (Added 5 / 14 / 2002) |
| Pre-mating isolation among demes of
the fishing spider Dolomedes triton : preliminary data. |
| Author: Kelly Kissane |
Institution: University of Nevada-Reno |
|
| Abstract: Dolomedes triton has the largest range
of the North American species, extending from southern Alaska to Mexico.
Variations in courtship behavior among the different populations have been
documented, though no study has explored whether these variations resulted
in reproductive isolation. A preliminary study of three populations in Ohio
indicates that the southernmost population (Athens) may be reproductively
isolated from the two more centrally located populations (Columbus and Marion).
Possible reasons for these observations are discussed. (Added 5 / 3 /
2002) |
| The systematics of nephiline spiders
(Araneae, Tetragnathidae) |
| Author: Matjaz Kuntner |
Institution: George Washington University
and the Smithsonian Institution |
|
| Abstract: Simon's argiopid subfamily Nephilinae consisted
of the genera Singotypa, Phonognatha, Deliochus, Nephila
(Nephilengys included), Clitaetra, and Herennia. Later,
Singafrotypa and Perilla were included in nephilines, and
Singotypa was synonymized with Phonognatha. Most earlier authors
placed Nephilinae within Araneidae, and recent authors moved it to Tetragnathidae.
Hormiga et al. (1995) analyzed a sample of 14 tetragnathid genera, including
five nephiline genera. The results supported the monophyly of Tetragnathidae
and a clade Nephilinae (Phonognatha (Clitaetra (Nephila
(Herennia + Nephilengys))) being sister to all other tetragnathids.
No phylogenetic placement has been hypothesized for Singafrotypa,
Perilla and Deliochus. This project focuses on a taxonomic
revision and systematics of all nephiline spiders. A preliminary phylogenetic
analysis of the latest morphological and behavioral data matrix corroborates
the monophyly of the following nephiline genera: ((Deliochus + Phonognatha)
+ (Clitaetra (Nephila (Nephilengys + Herennia)))).
However, the support for this nephiline clade is weak. This analysis supports
the recent transfer of Singafrotypa and Perilla to the araneid
subfamily Araneinae. It does not, however, corroborate the placement of
nephilines with tetragnathids. Instead, nephilines are here sister to Araneidae.
The implication of the single most parsimonious cladogram is that nephilines
are either an araneid subfamily, or alternatively deserve a family status,
which conflicts with all recent phylogenetic treatments of araneoids. However,
the data matrix is not complete, and most basal araneoid clades are weakly
supported in this phylogeny. Eliminating the missing entries, and increasing
the number of taxa, will provide a stronger test of the composition and
phylogenetic affinities of Nephilinae. (Added 6 / 1 / 2002) |
| Stabilimentum-associated anti-predator defences
of Argiope versicolor |
| Authors: Daiqin Li and Lai Mun Kok |
Institution: National University of Singapore |
|
| Abstract: Argiope versicolor (Araneae: Araneidae)
(Doleschall) is an orb-web spider that often adds conspicuous, white silk
designs known as stabilimenta around the hub. The forms of stabilimenta
are known to vary with developmental stages. Argiope versicolor juveniles
usually decorate the hub with a disc-like stabilimentum, while adult females
arrange their silk decorations as a cross. In this study, we investigated
stabilimentum-associated anti-predator defence behaviour of A. versicolor
both in the field and in the laboratory by addressing three questions: (1)
What are the major anti-predator defence behaviours used by A. versicolor?
(2) Is there any difference in anti-predator defence behaviour between juveniles
and adults? (3) Is an anti-predator defence behaviour stabilimentum-specific?
Four major anti-predator defence behaviours were identified for A. versicolor:
shuttling, shifting, pumping and dropping. Adults most frequently responded
to artificial stimuli with dropping and juveniles with shuttling. Dropping
was more frequently initiated than pumping. Disturbance on the leg and abdomen
was most likely to elicit a response from juveniles while adult females
were more likely to respond to leg disturbance only. No relationship between
stabilimentum and sensitivity to specific category of stimulus was found
in both juveniles and adults. However, A. versicolor showed stabilimentum-specific
anti-predator defence behaviours: juveniles shuttled between sides of the
webs with stabilimenta more often than of webs without stabilimenta, while
adult females dropped from webs without stabilimenta more frequently than
from webs with stabilimenta. Adult females were more likely to pump on the
webs with stabilimenta than on the webs without stabilimenta. (Added
5 / 15 / 2002) |
| Evidence for Interspecific Gene Flow
in the Habronattus amicus Species Complex (Araneae, Salticidae) |
| Authors: Michael Lowder and Marshal Hedin |
Institution: San
Diego State University |
|
| Abstract: Gene flow across species boundaries has rarely
been documented in spiders, perhaps because the phenomenon is rare, but
also because such processes are difficult to detect in nature. Here we present
evidence for interspecific gene flow occurring between H. amicus
(Peckham & Peckham) and H. cf. signatus, both members of the
Habronattus amicus species group. These species are distributed in
the western US, where they almost always occur in allopatry. However, we
have recently discovered multiple lake basins in the upper Great Basin (southeastern
OR, northeastern CA, and western NV) where these species are found together
on pluvial sand dunes. Multiple lines of molecular evidence suggest that
interspecific gene flow is occurring at some of these sites, perhaps in
a unidirectional manner (i.e., H. amicus genes are found in H.
cf. signatus, but the reverse is not true). This gene flow is taking
place despite obvious morphological and size differences between the taxa,
and despite preliminary evidence for fine-scale microhabitat differences.
These findings provide novel insights into processes of speciation and character
evolution in these jumping spiders. (Added 5 / 15 / 2002) |
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| Population divergence under sexual
selection in Habronattus pugillis (Salticidae) |
Authors and Institutions
| Wayne Maddison |
University of Arizona |
| Eileen Hebets |
University of Arizona |
| Susan Masta |
San Francisco State University |
|
|
Abstract: Montane populations of Habronattus pugillis
Griswold in southern Arizona, isolated by intervening desert, show many
fixed differences in male courtship characters (ornamentation and behavior).
A gene genealogy for mitochondrial DNA was reconstructed, and showed partial
but not complete differentiation among the mountain ranges. The shared retention
of some polymorphisms in mitochondrial genes contrasts against the fixation
of ifferences in the courtship characters, which are presumably under control
of nuclear genes. This contrast is statistically significant and points
to the courtship divergence being due to selection, given that under a neutral
model nuclear genes would be expected to show considerably more polymorphism
than mitochondrial genes. To explore the nature of selection on courtship
traits, we studied the reaction of females of two mountain ranges (Santa
Rita and Atascosa) to their own males and "foreign" males. These
two ranges are strikingly different in male traits: Santa Rita males have
a brown and white face, and engage in a slow display with palp circling
and leg waving, while Atascoca males have a silver face, and have a vigorous
sidling display. Atascosa females showed no strong preference, but Santa
Rita females accepted the "foreign" Atascosa males significantly
more frequently than their own males. This is consistent with the predictions
of a model of sexual selection by antagonistic coevolution (e.g. males exploiting
female sensory biases and females evolving resistance) but not with those
of a model of Fisherian runaway sexual selection.
(Added
5 / 13 / 2002) |
| Evidence for an ontogenetic shift in
retreat structure and placement in the Neotropical tarantula Ephebopus
murninus (Araneae: Theraphosidae) |
| Authors:Sam Marshall and Rick West |
Institution: Hiram College |
|
| Abstract: The theraphosid genus Ephebopus Simon,
1892, currently contains four Neotropical tarantula species which share
several unusual traits: they possesses a field of urticating hairs on the
prolateral surface of their pedipalpal femora, they are fossorial members
of an arboreal subfamily (the Aviculariinae), and they possess spatulate
tarsi and metatarsi, traits usually associated with an arboreal lifestyle.
We studied the retreat structure and placement of Ephebopus murinus
(Walckenaer, 1837) in a forest in French Guiana. We found that early-instar
spiderlings construct arboreal retreats in low vegetation, and only shifted
to a burrowing lifestyle when well grown. We also studied the placement
of the retreats and found that there were no obvious macrohabitat variables
that might determine retreat location. We suggest that the fossorial lifestyle
of subadult/adult E. murinus has evolved secondarily, and that this
might explain the burrow architecture, which is unique among New World theraphosids.
(Added 5 / 15 / 2002) |
| Microhabitat preferences of the scorpion,
Centruroides vittatus |
| Author: C. Neal McReynolds |
Institution: Texas A&M International University |
|
| Abstract: Microhabitat use by Centruroides vittatus
(Scorpiones: Buthidae) includes climbing vegetation. This study is to establish
if C. vittatus have preferences in the microhabitat selected. The
scorpions use of microhabitat did vary significantly at different research
sites on the campus of Texas A&M International University in the Tamaulipan
Biotic Province. The perennial plants selected by scorpions were compared
to the relative abundance of these plant species at the different research
sites. The relative abundance of perennial plants varied significantly at
different sites with the following species common: blackbrush, Acacia
rigidula; desert Christmas cactus, Opuntia leptocauli; prickly
pear cactus, Opuntia engelmannii; guajillo, Acacia berlandieri;
soapbush, Guaiacum angustifolium; and leatherstem, Jatropha dioica.
The plants selected by the scorpions at the different sites were significantly
different from the expected frequencies that were based on the relative
abundance of plant species. Scorpions did show a preference for some plant
species (e.g., blackbrush and strawberry cactus), but their relative abundance
did influence the plants selected. Two possible reasons for a microhabitat
preference can be higher abundance of prey on some plant species (blackbrush)
or as a refuge from predators and high temperatures during the day (strawberry
cactus). Future research will establish the effect of prey abundance and
microclimate on the microhabitat preferences of C. vittatus. (Added
5 / 15 / 2002) |
| Spiders collected from mangrove forest
in Mexico |
| Author: Francisco Medina and Areli Santos |
Institution: Universidad Nacional Autónoma
de México |
|
| Abstract: 1582 spiders were collected at 4 localities
of a mangrove forest during an expedition to Reserva La Encrucijada in the
coast of Chiapas state, Mexico, last April. Spiders were directly collected
from mangrove roots, foliage and ground where available, within a 3 hour
collecting effort replicated at day and night. Theridiidae was the most
abundant family among the web-spinning spiders with 495 specimens collected,
while among the wandering spiders, Ctenidae was the most abundant family
with 147 specimens. In contrast with the latter, comprised only of two genera
with one species each, Theridiidae showed greater diversity with 5 genera
and about 6 species identified as of yet. Up to now, 18 other families have
been identified out of the whole mangrove sample, including Senoculidae,
Dictynidae, Lycosidae, Oxyopidae, Scytodidae, Pisauridae, Corinnidae, Tetragnathidae
and Deinopidae. This is considerably more numerous compared with 5 families
recorded on the scarce information about this type of ecosystem from other
mangrove forests around the world (Australia, Singapore and United States).
All the families reported on such references are represented here, with
the only exception of one Barychelid from Australia, considered restricted
to that zone and in danger of extinction. These data are part of a major
study on mangrove spiders of the coast of Chiapas, Mexico. (Added 5 /
16 / 2002) |
| Representing Behavior: A case study
using Habronattus courtship |
| Authors: Peter Midford and Wayne Maddison |
Institution: University of Arizona |
|
| Abstract: Traditionally, the behavioral repertoire of
a species was collected and categorized in a descriptive document called
an ethogram. An ethogram is a catalog of terms for behavior patterns with
descriptions of those patterns. In the past two decades, the field of computer
science called knowledge representation has developed several methods for
representing everyday knowledge, such as behavior. The best developed of
these methods is the construction of machine "ontologies". An
ontology contains a hierarchical set of terms or concepts and a set of relations
among them. Terms are "defined" by their relationships with other
terms. Ontology-based representations of complex behavior may offer several
advantages over conventional ethograms. To illustrate the strengths and
weaknesses of each method, we constructed both an ethogram and an ontological
representation of courtship behavior in the Salticid Habronattus clypeatus.
We then extended the data set to H. californicus. We will present
both the ethogram and ontology-based representation of courtship behavior
for each species. (Added 5 / 14 / 2002) |
| Systematics of Neotropical Erigonine
Spiders (Araneae: Linyphiidae, Erigoninae): Are We Making Progress? |
| Authors: Jeremy Miller and Gustavo Hormiga |
Institution: The Smithsonian Institution and
George Washington University |
|
| Abstract: We present a new hypothesis of relationships
among erigonine spiders based mainly on morphological characters. We have
added taxa and characters to a previous analysis of erigonine relationships
by Hormiga (2000). Hormiga encoded 43 taxa including 31 erigonines for 73
characters. We have added 37 erigonine taxa to this matrix. All 80 taxa
are coded for 162 informative characters. Most of the characters in Hormiga's
analysis are included, sometimes in modified form. Nearly all of the taxa
added for the current analysis represent Neotropical genera. We evaluate
progress in our effort to understand erigonine phylogeny by studying the
impact of new taxa and characters on the relationships hypothesized in the
original study. To approach this, we prune all new taxa from the new analysis
and identify groups with identical composition in both Hormiga's (2000)
original cladogram and the pruned tree based on new characters and taxa.
We also reanalyze the original set of taxa using the expanded set of characters.
Finally, we use a new method, Continuous Jackknife Function analysis (Miller,
in prep.) to assess our progress toward a stable phylogenetic hypothesis.
Continuous Jackknife Function analysis uses character removal and a reference
hypothesis to evaluate the stability of the hypothesis under test. The results
are presented as a graph of the number of clades recovered after character
removal and reanalysis against the percent probability of character removal.
Stable phylogenies are expected to take the form of a decreasing asymptotic
curve with a high rate of clade recovery. (Added 5 / 8 / 2002) |
| A Comparative Study of Landscape Influences
on Spider Migration into Homes |
| Author: Carol O'Meara |
Institution: Denver Museum of Nature &
Science / CSU |
|
| Abstract: During 1999 and 2000, sixty percent of the
clients complaining to Colorado State University Cooperative Extension in
Boulder County about spiders in their homes claimed that their homes were
infested with more spiders than their neighbors living next door. The aim
of this study is to determine whether the complexity of landscaping around
a home decreases or increases the number of spiders entering the house.
To study this, a two-year survey of homes with simple and complex landscapes
is being conducted. Urban homeowners make decisions about the extent and
type of landscaping they plant around a house and this variation in landscape
structure may influence spider migration into homes on a house to house
basis. This study includes 20 houses with 5 glue traps each collected on
a monthly basis. Overall, 100 traps per month are collected with a total
of 2400 traps over the course of this survey. The sampled homes include
10 homes with simple landscapes and 10 homes with complex landscapes. For
the purposes of this survey, simple landscapes are those in which up to
30% of the square footage of the plantable property (not covered by buildings)
is in herbaceous or woody plantings. The remainder may be covered by turf,
mulch, rock, cement, or exposed soil. Complex landscapes have greater than
60% of the plantable area in herbaceous or woody plantings. Fourteen months
of data will be discussed, and there appears to be a correlation between
complex landscapes and higher numbers of spiders in homes. (Added 5 /
9 / 2002) |
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| Spiders of Québec (an identification
guide) |
| Authors: Pierre Paquin and Nadine Dupérré |
Institution: San Diego State University |
|
| Abstract: The spider fauna of the province of Québec
actually lists 623 species and the occurence of another 147 is suspected
(Paquin et al. 2001). We are here presenting a monograph that will
be a major tool for the identification of spiders species of Eastern North
America. It includes illustrated keys to families and genera (except Linyphiidae)
and genitalias of all species are fully illustrated. We have used comparable
angles within each genera to allow an easier recognition of diagnostic characters.
The book contains 180 plates (4 species each) presented in a 8.5 x 11 format
with a spiral binding to facilitate handling in the lab. Samples of key
and plates are given. (Added 5 / 31 / 2002) |
| Spatial and Temporal Distribution of
Sympatric Species of Agelenopsis and Barronopsis |
| Author: Marius Pfeiffer |
Institution: University of Texas at Arlington |
|
Abstract: Much work has been done to determine the importance
of interspecific competition in moderation of population and distribution
of numerous species. Within arachnida recent results have suggested that
interspecific competition is not a major ecological force. Additional investigation
of natural systems, both passive and manipulative is required for clarification
of ambiguities.
A two year survey study was undertaken to
determine spatial and temporal distribution of sympatric populations of
the genera Agelenopsis and Barronopsis along a road boundary
in a riparian habitat. The objective of the study was to determine, indirectly,
if the potential for interspecific competition exists between ecologically
similar members of closely related genera. Significant overlap of spatial,
temporal or substrate use characteristics is considered as suggestive of
competitive potential. Significant partitioning of any of these characteristics
is considered as indirect evidence for avoidance of competition (Ghost of
Competition Past). Ten 5x20m quadrats were surveyed three times per year
for the first year and for the spring of 2002. Species, size, 3 axis positional
data, substrate and activity were noted for all identifiable animals. Results
so far suggest temporal segregation of life histories and spatial segregation
among species and based on animal size within species. (Added 5 / 15
/ 2002) |
Systematics of Island and Mainland Populations
of B. californicum
(Araneae,
Ctenizidae) |
| Authors: Martin Ramirez and Brian Cashin |
Institution: Loyola Marymount University |
|
| Abstract: Bothriocyrtum californicum is a large
California trapdoor spider. B. californicum samples were collected
from six mainland sites in Los Angeles, Orange and San Diego Counties, as
well as from Santa Catalina and Santa Cruz Islands, and were assayed for
variability at 11 allozyme loci. Estimates of genetic variability for B.
californicum are comparable to those of other non-social spiders. A
phylogeny for these populations shows that the Otay Mesa population is basal
in the phylogeny and the remaining populations are placed in two monophyletic
groups: populations of central/northern Los Angeles Co.; and populations
from inland Los Angeles Co. to coastal Orange Co. The fact that most populations
fall into these two groups may be associated with geologic changes that
occurred in this region beginning in the Pliocene. During this time the
Los Angeles basin was flooded, which coupled with the northward extension
of the Sea of Cortez, severely restricted the movement of organisms to and
from Baja California at its northern end until the Pleistocene. This San
Gorgonio Barrier has been implicated as a historic biogeographic obstacle
for the movements of vertebrate taxa and may be the cause of the evolution
of northern and southern mainland groups of B. californicum. (Added
5 / 14 / 2002) |
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| The Recluse Community Project: The
project designed with the people in mind |
| Author: Jamel Sandidge |
Institution: University of Kansas |
|
| Abstract: The brown recluse spider Loxosceles reclusa
is implicated in medical emergencies in North America each year, leaving
many people with open wounds and unsightly scars (necrotic arachnidism),
and an intense fear of spiders (loxoscelism). Presently, there are no reliable
diagnostic tests to positively identify brown recluse bites. There is no
widely distributed antivenom or medically proven treatment, which presents
a serious medical dilemma. Controlling infestations has proven to be difficult,
and is thought to be impossible. Despite the large number of medical research
articles on the components, activity, and destructiveness of Loxosceles
reclusa venom, none are devoted directly to exploring the crucial and
most essential element of the system -- the spider populations themselves.
The Recluse Community Project is a three-year project consisting of four
primary areas: public education and awareness, population biology, molecular
population genetics, and biological invasion and population monitoring.
The immediate and most critical components of this project are to increase
our limited knowledge of the behavior, population dynamics and genetics
of this clinically significant spider for the benefit of all. These factors
may help to reduce the probability of accidental envenomations and associated
medical emergencies by providing a clear description of species movements,
periods of activity, and patterns of biological invasion. This research
is original in that is takes public paranoia, issues of public health and
safety, as well as an intense fear of the unknown to solicit public involvement
while creating a public fascination for science. (Added 5 / 17 / 2002) |
| Who preys on the ultimate predator:
Life history strategies of the vinegaroon, Mastigoproctus giganteus |
| Author: Justin Schmidt |
Institution: Southwestern Biological Institute |
|
Abstract: Vinegaroons, large generalist ambush predators,
are often considered curiosities rather than major factors shaping communities.
In some areas they likely are the most important predator in the system,
and, importantly, prey on large numbers of other top predators including
scorpions, sulpugids, and lycosids. Vinegaroons are famous for their defensive
capabilities, especially their acid-rich spray. A natural question: if vinegaroons
are dominant predators, who preys on them, and what factors are limiting
in their life history?
To understand the forces shaping the biology of vinegaroons, prey records
from hundreds of hours in the field were analyzed and manipulative laboratory
tests were conducted. No vinegaroon of any size or instar was ever observed
to be preyed upon in the field and no remnants (pedipalp/leg fragments)
were discovered. Laboratory investigations suggest adults die in their overwintering
cells rather than being predated. Immatures are rarely seen in the field
and might be the vulnerable link in the life cycle. Staged encounters revealed
that the defenses of even the first instar free-living immatures are only
rarely overcome by predators. Predators most able to endure the acid spray
of immatures were large adult lycosids, and carabid beetles and tarantulas.
However, even with these predators, success was achieved mainly when the
attack was such that the defensive spray was avoided. The results suggest
that vinegaroon life history is limited by low reproductive potential, abiotic
factors, shortage of food, and some predation on first and second instar
individuals by a few species of large spiders or insects. (Added 4 /
18 / 2002) |
| A Glimpse into the Diversity and Endemism
of Malagasy Spiders |
| Author: Diana Silva |
Institution: California Academy of Sciences |
|
| Abstract: Madagascar is an island in the Indian Ocean
separated from Africa since the late Cretaceous, approx. 130 mya. This island,
often referred as a "museum of living fossils" for harboring very
old phylogenetic lineages, has been the focus of major conservation efforts
due to 1) its high levels of endemism for various groups of plants and animals,
and 2) the highly threatened status of numerous taxa as a result of deforestation
of native habitats and introduced exotic species, among other factors. Through
multidisciplinary efforts of various research centers, such as the California
Academy of Sciences, a sampling protocol including a wide range of techniques
has been designed to document the biodiversity of Madagascar. This report
shows the family composition of all spiders recorded from this island after
two years of intensive field work, the species richness of the spider communities,
and comparisons of the species diversity and distribution patterns of such
families as the ctenids (57 spp), gnaphosids (33 spp), lycosids (15 spp),
mimetids (12 spp), and sparassids (64 spp). Although available data do not
allow comprehensive phylogenetic analyses for most spider families, a cladistic
analysis for the Ctenidae suggests that the Malagasy ctenids comprise two
lineages; one of them, the viridasines, appear to be the most basal lineage
of the family. (Added 5 / 14 / 2002) |
| A Survey of the terrestrial non-insect
macroarthropods of Toft Point Natural Area, Wisconsin |
| Authors: Bruce Snyder and Michael Draney |
Institution: University of Wisconsin Green Bay |
|
Abstract: Toft Point Natural Area is a National Natural
Landmark owned and managed by the University of Wisconsin Green Bay
and is located on the Lake Michigan shore of Wisconsin's Door Peninsula.
With twelve different biotic communities on 700 acres, Toft Point is biologically
diverse. We attempted a preliminary survey of the terrestrial non-insect
macro-arthropods, which include most of the non-aquatic arthropods except
insects and mites; specifically, arachnids (spiders and harvestmen), myriapods
(centipedes and millipedes), and terrestrial isopods (crustaceans). We sampled
on May 2, July 17, and September 22, 2001. One concentrated, spatially integrated
litter sample was collected at each of five habitats during each date; these
were then Berlese extracted. A timed hand collection was also used, consisting
of 0.5 person-hour/site/date, using a combination of techniques, including
sweeping herbaceous vegetation, brushing/beating woody vegetation, and hand
searching with aspirators within vegetation and at ground level, including
turning over rocks and logs.
The 35 samples collected covered
nine different habitats. Three of the twelve isopod species known in Wisconsin
were found at Toft Point. Five families of myriapods were found, including
Polyzoniids rarely found in Wisconsin. 91 species of spiders in 17 families
were found, including 60 new to Toft Point, 46 new to Door County, and 10
new Wisconsin state records. These include two southern and two western
range extensions. The Polyzoniids and eight of the state records were collected
by leaf litter extraction, mostly from wetland habitats. (Added 5 / 7
/ 2002) |
| Molecular Phylogenetic Analysis of North
American Grass-spiders (Araneae: Agelenidae) |
| Author: Joseph Spagna and Rosemary Gillespie |
Institution: U.C. Berkeley |
|
| Abstract: The family Agelenidae (Koch 1837) is large
(42 genera, 490 described species) and a number of spiders from this family
have been used as models for toxicological and behavioral research. Despite
this use, to date little phylogenetic work has been done on these taxa,
thus there is little information on the evolutionary context of this research.
In the Agelenidae, there are eight genera (Hololena, Rualena, Calilena,
Novalena, Agelenopsis, Barronopsis, Tortolena and Melpomene)
endemic to North and Central America. Cladistic analysis of molecular sequence
data from mitochondrial (cytochrome oxidase 1 and 16S ribosomal DNA) and
nuclear (28S rDNA) genes suggests a monophyletic group confined to the Western
U.S. (Calilena (Hololena (Novalena + Rualena))),
which relates distantly to the more widespread Agelenid genera Agelenopsis
and Tegenaria. Preliminary analysis of distributions of subsets of
morphological and behavioral characters suggests that while differences
between species within each genus is primarily based on genitalic structure,
one of the primary differences between the genera appears to be choice of
web-substrate. I am using these patterns of character changes to examine
ecological and morphological correlates of diversification on temporal and
spatial scales. (Added 5 / 16 / 2002) |
| Response of male Centruroides vittatus
to aerial and substrate-borne chemical signals |
| Authors: Steffany Steinmetz and Douglas Gaffin |
Institution: University
of Oklahoma |
|
| Abstract: From insects to primates, chemical signaling
aids in the success of mate location. In this study we investigated the
possibility that striped scorpions, Centruroides vittatus, use air or ground
based chemical cues as a channel of intraspecific communication. A Y-shaped
arena was constructed to test scorpions' use of olfactory signals to detect
potential mates. A second behavioral choice chamber (similar to that used
by previous investigators) was used to test male scorpions' responses to
female deposits by direct substrate contact. Male scorpions showed no tendency
to move toward females in tests of air-borne chemical transmission. A preliminary
test of male response to female deposits suggested some tendency to move
to the regions previously occupied by a female. However, subsequent trials
showed no bias in male movements relative to potential female deposits.
Under the conditions of these laboratory experiments, males did not appear
to detect females via air or ground based chemicals. We will repeat this
set of experiments during late summer / early fall to test for possible
seasonal effects on mate signaling in C. vittatus. (Added 5 /
12 / 2002) |
| Diagnosis and Therapy of Loxosceles
reclusa (brown recluse spider) bites |
Authors and Institutions
| W. Van Stoecker |
The Dermatology Center, Rolla, MO |
| Hernan Gomez |
University Michigan |
| Jennifer L. Parks |
Univ. Missouri-Rolla |
|
|
| Abstract: Envenomations by North American Loxosceles
spiders, most commonly represented by the brown recluse spider L. reclusa,
are frequently misdiagnosed. This presentation reviews clinical aspects
of envenomations including the typical symptoms, physical findings, and
diagnostic tests. Key therapeutic interventions include the RICE regimen
and dapsone if the area of necrosis exceeds 1 cm^2 Emerging diagnostic tests
include ELISA tests using either polyclonal or monoclonal antibodies. Which
clinical features are most important in making the diagnosis of "necrotic
arachnidism?" What variants are possible and which findings are more
suggestive of clinically similar diagnoses? Very large ulcers, multiple
skin lesions, and early ulceration all lead us to alternate diagnoses. This
presentation will include brief clinical descriptions of the foremost confounding
diagnoses including envenomations by other arthropods, pyoderma gangrenosum
and factitial causes of skin necrosis. We will summarize the approximately
90 documented Loxosceles envenomations in North America, a very small
number considering the thousands of diagnosis of "spider bites"
that are made each year. (Added 5 / 18 / 2002) |
| Trichobothrial mediation of an escape
response: Vertical jumps by Dolomedes triton foil frog attacks |
| Authors: Robert B. Suter and Nura Farah |
Institution: Vassar College |
|
| Abstract: Jumps of fishing spiders (Dolomedes
sp.) from the water surface have been presumed to be evasive behaviors directed
against predators. In an earlier study, we analyzed the jumps of fishing
spiders and demonstrated that jump heights and durations were inadequate
to provide protection against strikes from below by fish. We report here
(1) that attacks from the side by large frogs (Ranidae) are effectively
evaded by the vertical jumps of the spiders, (2) that leg-borne trichobothria
appear to be the primary sensory mediators of the evasive behavior, and
(3) that the kinematics of the air just above the water surface can effectively
mask the attack of a frog. In a quasi-natural laboratory setting, spiders
frequently (in 25 of 30 trials) made no attempt to evade attacks by bullfrogs
and green frogs; but when the spiders did attempt evasion by jumping, they
escaped uninjured in 4 of 5 trials. When we measured the responses of intact
spiders and spiders with disabled trichobothria to sham attacks by a mechanically
propelled, freeze-dried bullfrog, we found that the absence of trichobothrial
input nearly obliterated the evasion response. Preliminary results indicate
that during attacks in which the spiders make no attempt at evasion, the
air movements that signal an attack are probably effectively masked by "noisy"
ambient air. (Added 4 / 15 / 2002) |
| New spiders from California (Araneae:
Amaurobiidae) |
| Author: Darrell Ubick |
Institution: California Academy of Sciences |
|
| Abstract: Three new species of spiders are described
from California. The first is from the southern Sierra foothills in Tulare
County and the other two are from the Mojave region: Granite Mountain (sp
2) and a series of localities from Riverside to Imperial counties (sp 3).
All three are small cribellate spiders with similar somatic morphologies
and appear related because of synapomorphies of the male genitalia, the
most striking of which are an unusual retrolateral furrow on the cymbium
and a tripartite RTA. It is argued that the species represent two new genera
(1 + (2 + 3)) which are most closely related to Zanomys. This zanomyine
complex is defined on the basis of a shared sexual dimorphism (males with
a laterally expanded carapace) and is the likely sister group of the subfamily
Coelotinae, whose members have a similar retrolateral furrow on the cymbium.
The family placement of this clade is not certain as it shows affinities
to both the Amaurobiidae and Agelenidae. (Added 5 / 13 / 2002) |
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V through X
| A comparison of the diversity of
ground dwelling spiders in old-growth beech-maple with a second-growth forest |
| Authors: Melissa Varrecchia and Maggie Hodge |
Institution: Hiram College |
|
| Abstract: Beech-maple forests were once widespread throughout
Ohio and Indiana, but are now restricted to a few small remnant sites. We
report on preliminary findings of a study designed to measure and compare
species turn-over rates in a pristine 200 acre beech-maple forest and an
adjacent, second growth forest at the J.H. Barrow Field Station in northeast
Ohio. Eight pairs of pitfall traps were sampled in each habitat at weekly
intervals from May-August 2001. Abundance, familial and generic diversity
as well as various phenological patterns will be presented. (Added 5
/ 22 / 2002) |
| Title: The
myth of the brown recluse spider: myth-takes, myth-identifications and
myth-diagnoses |
| Author: Rick Vetter |
Institution: University of California at Riverside |
|
| Abstract: The brown recluse spider, Loxosceles reclusa,
is rarely found outside of its endemic range (southeastern Nebraska to southernmost
Ohio, south to Texas and Georgia). Despite the fact that brown recluses
are extremely rare in non-endemic areas, the general public and the medical
community believe that the spider is common throughout the United States
and is the cause of mysterious wounds of unknown etiology. The annual number
of medical diagnoses of brown recluse bites in many non-endemic states or
regions is tens to hundreds times greater than the historic total of verified
brown recluses from the area. In endemic areas, individual homes can be
infested annually with more brown recluses than can historically be documented
in several American states and often, no one from these Midwestern homes
shows evidence of a bite. The myth of the brown recluse is kept alive by
medical misdiagnoses, misidentifications of harmless common spiders, hyperbolic
news media and erroneous public perception. The danger lies in that because
the diagnosis of "brown recluse spider bite" is so readily accepted
by both the medical community and their patients in non-endemic areas, these
misdiagnoses mask a plethora of medical maladies which manifest themselves
in dermatologic eruptions. Although many of these maladies are innocuous
with no long-term effects, several conditions (such as Lyme disease, anthrax,
necrotizing bacteria, lymphoma, leukemia) can be debilitating or fatal if
the ailment is misdiagnosed and remedy is delayed or incorrect. (Added
3 / 17 / 2002) |
|
| The distribution of the hobo spider,
Tegenaria agrestis, in the United States and Canada |
Authors and Institutions
| Richard S. Vetter |
University of California, Riverside |
| Alan H. Roe |
Utah State University, Logan |
| Robert G. Bennett |
British Columbia Ministry of Forests, Saanichton |
| Craig R. Baird |
University of Idaho, Parma |
| Lynn A. Royce |
Oregon State University, Corvallis |
| William T. Lanier |
Montana State University, Bozeman |
| Arthur L. Antonelli |
Washington State University, Puyallup |
| Paula E. Cushing |
Denver Museum of Nature and Science, Denver CO |
|
|
| Abstract: Since the late 1980s, the hobo spider has
been implicated in necrotic wounds in the northwestern United States and
British Columbia, Canada. Before this, necrotic wounds were blamed on the
brown recluse spider even though there were no recluse populations there.
Because it is a spider and because it is blamed for causing wounds, the
hobo spider is the subject of much hyperbole. Sources of information are
usually regional in scope or come from non-arachnologists, hence they are
subject to misintrepretation and exaggeration. Along with 7 collaborators,
I coordinated a study to determine where the hobo spider is found. The current
known range is from southern British Columbia to southern Oregon and eastward
to central Montana, western Wyoming and northern Utah. All of Washington
and Idaho are considered within the range of the hobo spider. There are
two reliable isolated populations associated with two houses in Colorado.
This study also mapped out the distribution of the giant house spider, Tegenaria
duellica (synonymizations include T. saeva and T. gigantea)
which is found on the Pacific side of the mountains in British Columbia,
Washington and Oregon, is more common than the hobo spider in most human
population centers where the two species are found, is considered harmless
but is often misidentified as a hobo spider by non-arachnologists. (Added
5 / 10 / 2002) |
| Observations on courtship, mating, maternal
care and subsocial behavior of the East African tarantula Heterothele
villosela (Araneae: Theraphosidae) |
| Author: Amanda Weigand, Barbara Vasquez and
Sam Marshall |
Institution: Hiram College |
|
| Abstract: Spider sociality is a rare phenomenon, being
observed in less than 0.1% of described species. We studied the reproductive
behavior, maternal care, and spiderling social behavior of Heterothele
villosela Strand, 1907, a small theraphosid in the subfamily Ischnocolinae
from East Africa. This genus is phylogenetically enigmatic, having been
recently moved between different genera and even families. The current hypothesized
placement of this genus places it in a poorly-defined group of small and
widely distributed tarantula species. Ours will be the second description
of the sociality in Heterothele, and one of the few studies of the
social behavior any tarantula. We acquired 32 H. villosela collected
in Tanzania from a commercial importer. The spiders were held in 1.0 liter
plastic containers with a bark mulch substratum, a piece of bark for a refuge,
and a small water dish. The spiders are fed twice weekly on domestic crickets.
The cages were held in a humidified, heated room (27oC and 20% rh) with
ambient sunlight for photoperiod. We paired spiders and videotaped the courtship
and/or matings. We generated ethograms of the behaviors observed and compared
successful to unsuccessful courtships. We also observed the interactions
of the females and offspring. (Added 5 / 15 / 2002) |
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Y and Z
| ITS2 rDNA variation of two black widow
species, Latrodectus mactans and Latrodectus hesperus |
| Authors:Daiyuan Zhang, Bill Cook, and Norman
Homer |
Institution: Midwestern State University |
|
Abstract: The taxonomic status of two closely related
species of Latrodectus, L. mactans and L. hesperus,
has been debated for many years. Based on morphological characteristics
and genitallia, some workers consider them valid species and others as subspecies.
The purpose of this project was to determine whether the internal transcribed
spacers 2 (ITS2) of rDNA from the two taxa exhibit sequence differences
which could shed light on their taxonomic relationship.
Individuals
of Latrodectus mactans and Latrodectus hesperus from six populations
were collected and identified based on reported morphological characteristics.
The ITS2 rDNA of 9 individuals were sequenced and analyzed. Results suggest
that: 1) ITS2 sequences in the two taxa exhibit minimal differences. 2)
The assignment of the two taxa to seperate species is not supported by ITS2
sequences comparison. (Added 5 / 8 / 2002) |
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