Home About us Contact
|
Home About us Contact | ||
|
|
||
Spiders
Kinds of Spiders Terms modified by Spiders Selected AbstractsSPIDER: A decade of measuring ultrashort pulsesLASER PHYSICS LETTERS, Issue 4 2008M.E. Anderson Abstract It was ten years ago in Rochester, New York that the first SPIDER was built. This simple acronym belies the subtleties of its inner workings; Spectral Phase Interferometry for Direct Electric-field Reconstruction (the "f" in field conveniently missed the cut) is a device that measures ultrashort pulses, utilizing spectral shearing interferometry and directly recovering the spectral phase. The very first SPIDER apparatus occupied nearly half an optical table, used a scanning monochromator, and had no computerized inversion routine. In the intervening decade, SPIDER has grown up. It has found a strong foothold in ultrafast laboratories throughout the world. Multiple groups have found useful new applications with this vital measurement tool, while others have contributed to the improvement of SPIDER itself, reaching to ever shorter pulses, new wavelength regimes, and making devices more sensitive, robust, smaller and faster. It also adapts to a field of research that changes rapidly. It was first designed to track and quantify the remaining spectral phase in a pulse to perfect its compression. In ten years, with the advent of pulse shapers, the real benefits of field diagnostics are becoming apparent. We have shifted away from the race towards the shortest IR pulse to a wide use of complex shaped pulses in almost every spectral range from far IR to XUV. But the quest of the shortest pulse is not over and new compression techniques utilize really broad spectra that are highly structured. All these applications provide new challenges for characterization techniques. (© 2008 by Astro Ltd., Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source] A NEW SEA SPIDER (ARTHROPODA: PYCNOGONIDA) WITH A FLAGELLIFORM TELSON FROM THE LOWER DEVONIAN HUNSRÜCK SLATE, GERMANYPALAEONTOLOGY, Issue 5 2006MARKUS POSCHMANN Abstract:, A new Lower Devonian sea spider (Arthropoda: Pycnogonida) from the Hunsrück Slate, Germany, is described as Flagellopantopus blocki gen. et sp. nov. This is only the sixth fossil pycnogonid species to be described. Its most remarkable and unique aspect is the long, flagelliform telson. Although our fossil apparently lacks chelifores (an apomorphy), the retained telson and the segmented trunk end behind the last pair of legs resolve F. blocki to a fairly basal position in the pycnogonid stem lineage. It probably lies between Palaeoisopus problematicus Broili, which has a lanceolate telson and the most trunk segments of any sea spider, and all other Silurian,Recent Pycnogonida. Our new material shows that at least two fossil pycnogonids retained a telson, albeit with very different morphologies, and further supports the idea that a greater diversity of body plans existed among the Palaeozoic pycnogonid taxa. [source] SOCIALITY IN THERIDIID SPIDERS: REPEATED ORIGINS OF AN EVOLUTIONARY DEAD ENDEVOLUTION, Issue 11 2006Ingi Agnarsson Abstract Evolutionary ,dead ends' result from traits that are selectively advantageous in the short term but ultimately result in lowered diversification rates of lineages. In spiders, 23 species scattered across eight families share a social system in which individuals live in colonies and cooperate in nest maintenance, prey capture, and brood care. Most of these species are inbred and have highly female-biased sex ratios. Here we show that in Theridiidae this social system originated eight to nine times independently among 11 to 12 species for a remarkable 18 to 19 origins across spiders. In Theridiidae, the origins cluster significantly in one clade marked by a possible preadaptation: extended maternal care. In most derivations, sociality is limited to isolated species: social species are sister to social species only thrice. To examine whether sociality in spiders represents an evolutionary dead end, we develop a test that compares the observed phylogenetic isolation of social species to the simulated evolution of social and non-social clades under equal diversification rates, and find that sociality in Theridiidae is significantly isolated. Because social clades are not in general smaller than their nonsocial sister clades, the spindly phylogenetic pattern,many tiny replicate social clades,may be explained by extinction rapid enough that a nonsocial sister group does not have time to diversify while the social lineage remains extant. In this case, this repeated origin and extinction of sociality suggests a conflict between the short-term benefits and long-term costs of inbred sociality. Although benefits of group living may initially outweigh costs of inbreeding (hence the replicate origins), in the long run the subdivision of the populations in relatively small and highly inbred colony lineages may result in higher extinction, thus an evolutionary dead end. [source] RESISTANCE OF SPIDERS TO CRETACEOUS-TERTIARY EXTINCTION EVENTSEVOLUTION, Issue 11 2003David Penney Abstract Throughout Earth history a small number of global catastrophic events leading to biotic crises have caused mass extinctions. Here, using a technique that combines taxonomic and numerical data, we consider the effects of the Cenomanian,Turonian and Cretaceous,Tertiary mass extinctions on the terrestrial spider fauna in the light of new fossil data. We provide the first evidence that spiders suffered no decline at the family level during these mass extinction events. On the contrary, we show that they increased in relative numbers through the Cretaceous and beyond the Cretaceous,Tertiary extinction event. [source] Fine Structural Analysis of the Silk Apparatus in the Funnel-web Spider, Agelena limbata (Araneae: Agelenidae)ENTOMOLOGICAL RESEARCH, Issue 4 2002Jong-Gu PARK ABSTRACT Silk apparatus of the funnel-web spider, Agelena limbata was located at the ventral end of the abdominal part, and was composed of internal silk glands and external spinnerets. Among the three pairs of spinnerets, the posterior pairs were highly elongated along the body axis. By the light and electron microscopic inspections, it was found that four types of silk glands were connected through the typical spinning tubes of each spinneret. Anterior spinnerets comprise 2 pairs of the ampullate and 125 to 150 pairs (female) or 110 to 114 (male) of pyriform glands. Another 2 pairs of ampullate glands in both sexes, 5 to 8 pairs of tubuliform glands in females, and 20 to 26 pairs (female) or 15 to 17 pairs (male) of aciniform glands were connected on the median spinnerets. Additional 8 to 10 pairs of tubuliforms in female and 41 to 53 pairs (female) or 27 to 32 pairs (male) of aciniform glands were on the posterior spinnerets, respectively. While the ampullate and tubuliform glands were connected with the spigot-type spinning tubes, the pyriform and aciniform glands with that of spool-type tubes. It has been also revealed that the tubuliform glands were only observed in female spiders, however the flagelliform and aggregate glands which had the function of adhesive thread production in orb-web spiders were not observed at both sexes of this spiders. [source] Social Environment and Feeding State Influence Movement Decisions in a Web-building SpiderETHOLOGY, Issue 10 2009Maxence Salomon It is well recognized that feeding rate has a major influence on the amount of movement between microhabitats for many animals. However, the role of other extrinsic and intrinsic factors, and particularly how these factors may interact, is not well understood. This three-part study examines the movement decisions of a web-building spider, Latrodectus hesperus, by assessing microhabitat tenacity in established spiders and by testing how the presence of conspecific neighbours and the combined influence of individual feeding state (determined by prior feeding experience) and neighbour presence influence microhabitat residence time in unestablished spiders. The results show that naturally established spiders did not leave their microhabitats readily, emphasizing the importance of choosing a profitable location. Unestablished spiders stayed longer in microhabitats occupied by conspecifics than in unoccupied ones, and there was practically no cannibalism even though neighbours shared webs. Furthermore, feeding state and neighbour presence showed an interactive effect on microhabitat residence time. When spiders were housed alone, microhabitat residence time increased with feeding state. However, in the presence of conspecifics, spiders had a low propensity to move, regardless of feeding state. Together, these results demonstrate the combined importance of grouping dynamics and feeding state in shaping movement decisions. [source] Scent of a Woman , The Effect of Female Presence on Sexual Cannibalism in an Orb-Weaving Spider (Araneae: Araneidae)ETHOLOGY, Issue 7 2009Stefan H. Nessler Post-mating sexual cannibalism occurs as a regular element of mating behaviour in a number of spider species. Frequencies of cannibalism, however, are highly variable between and within species. In Argiope bruennichi, males apparently differ in their motivation to escape a female attack but causes for this variability are unknown. We observed that the probability of sexual cannibalism is positively correlated with male age, i.e. the number of days that passed between male maturation and copulation. The mating season in this species is short with 3,4 wk and males mostly mature days before the females, whose maturation phase is longer. Consequently, as the season progresses, the availability of virgin females increases, quickly reaches a peak and then rapidly declines. In addition, the age of still unmated males increases with the season and both of these factors can potentially affect the degree of sexual cannibalism. To separate these factors, males were collected in their penultimate stage and kept until mating either with or without contact to female pheromones. Thereby, we experimentally manipulated the male's perception of female presence. Within each treatment, we formed three male age groups: (1) 2,6 d, (2) 12,16 d and (3) 22,28 d. Our results demonstrate that the probability of cannibalism was independent of male age but was explained by the treatment of males: males exposed to virgin female pheromones were significantly more likely to be cannibalised than males that were kept without female pheromones. This suggests that males change their reproductive strategy according to perceived mating prospects. [source] Male Competition over Access to Females in a Spider with Last-Male Sperm PrecedenceETHOLOGY, Issue 5 2003Daniela Schaefer Agonistic behaviour between male cellar spiders (Pholcus phalangioides) was investigated to test whether (1) size difference determines which male achieves access to the female, (2) males are able to monopolize access to the female until egg laying and whether (3) female resource value increases before egg laying because of last-male sperm precedence. We further investigated whether (4) there is variation in time and energy spent on courtship and copulation depending on the degree of sperm competition, i.e. with or without rival present. In three experimental settings we introduced two males of either different or similar sizes, or a single male to a female. The mating units were constantly video-observed until the females produced their first egg sac. Experience, ownership and female resource value in terms of body size was controlled. Our results show that larger males achieve almost exclusive access to females. Size symmetrical settings resulted in increased fighting activity and duration but dominance did not influence mating success. If copulations were disturbed by the rival male, copulations were terminated earlier in symmetrical settings compared with asymmetrical settings. In 94.8% of trials only one copulation took place, suggesting that the copulating male successfully monopolized access to the female. Males confronted with a rival copulated longer but courted significantly shorter than lone males. Although the last male to copulate sires 88% of the offspring in P. phalangioides, neither fighting nor courtship activity increased before the female laid a batch of eggs. This suggests that males have no indication of the timing of oviposition. [source] Contemporary use of embolic protection devices in saphenous vein graft interventions: Insights from the stenting of saphenous vein grafts trial,CATHETERIZATION AND CARDIOVASCULAR INTERVENTIONS, Issue 2 2010Neeraj Badhey MD Abstract Background: We sought to evaluate the contemporary use of embolic protection devices (EPDs) in saphenous vein graft (SVG) interventions. Methods: We examined EPD use in the stenting of saphenous vein grafts (SOS) trial, in which 80 patients with 112 lesions in 88 SVGs were randomized to a bare metal stent (39 patients, 43 grafts, and 55 lesions) or paclitaxel-eluting stent (41 patients, 45 grafts, and 57 lesions). Results: An EPD was used in 60 of 112 lesions (54%). A Filterwire (Boston Scientific) was used in 70% of EPD-treated lesions, Spider (ev3, Plymouth, Minnesota) in 12%, Proxis (St. Jude, Minneapolis, Minnesota) in 12%, and Guardwire (Medtronic, Santa Rosa, California) in 7%. Of the remaining 52 lesions, an EPD was not utilized in 13 lesions (25%) because the lesion was near the distal anastomosis, in 14 lesions (27%) because of an ostial location, in one lesion (2%) because of small SVG size, in two in-stent restenosis lesions (4%) because of low distal embolization risk, and in 22 lesions (42%) because of operator's preference even though use of an EPD was feasible. Procedural success was achieved in 77 patients (96%); in one patient a Filterwire was entrapped requiring emergency coronary bypass graft surgery and two patients had acute stent thrombosis. Conclusion: In spite of their proven efficacy, EPDs were utilized in approximately half of SVG interventions in the SOS trial. Availability of a proximal protection device could allow protection of ,25% of unprotected lesions, yet operator discretion appears to be the major determinant of EPD use. © 2010 Wiley-Liss, Inc. [source] The influence of scale and patchiness on spider diversity in a semi-arid environmentECOGRAPHY, Issue 4 2002Mary E. A. Whitehouse Semi-arid scrubland in the Middle East consists of a soil crust matrix overlain with patches of perennial shrubs. To understand factors influencing biodiversity in this vulnerable landscape we need to understand how this mosaic of habitats influences associated fauna. Spiders are particularly abundant in this habitat so we asked if spider diversity differed between habitat patches and if different patch types contained either a subset of the regional species pool or specific species guilds. We also asked whether changes in the fractal nature of the microphytic and macrophytic patch mosaic altered spider diversity in this habitat. We found that the semi-arid scrubland at Sayeret Shaked Park (Israel) contains different spider communities that require patches of a certain quality to develop fully. Different patch types contain communities of different species, but the community structure of the patches is similar. We suggest that large-scale environmental factors typical of the site as a whole influence coarse-grained community structure, while small-scale differences between patch types result in the specialisation of species to different patch types. [source] Sublethal responses of wolf spiders (Lycosidae) to organophosphorous insecticidesENVIRONMENTAL TOXICOLOGY, Issue 5 2002S. Van Erp Abstract The activities of cholinesterase (ChE) and glutathione S -transferase (GST) enzymes were assessed in the wolf spider (Lycosa hilaris) as biomarkers of organophosphate contamination in agricultural ecosystems. Spiders were exposed to simulated field rates of two commercially available organophosphorous insecticides [Basudin (diazinon) and Lorsban (chlorpyrifos)] under laboratory conditions. In terms of survival, chlorpyrifos and diazinon were more toxic to male than to female wolf spiders, but gender-specific differences in ChE activities were not evident. Cholinesterase activity in male spiders was inhibited to 14% and 61% of control activity by Basudin and Lorsban, respectively. Gluthathione S -transferase activity was not affected by either pesticide. Mortality and biomarker responses in the wolf spider were further investigated following the application of Basudin to pasture. Wolf spiders were deployed into field mesocosms; after 24 h mortality was 40%, and surviving spiders displayed significant inhibition of ChE activity (87%) compared with controls. Cholinesterase activity in spiders exposed for subsequent 24- or 48-h time periods was monitored until it returned to control levels 8 days post-application. Inhibition of ChE activity after a single application of Basudin indicate the potential use of this enzyme in wolf spiders as a biomarker for evaluating organophosphate contamination. © 2002 Wiley Periodicals, Inc. Environ Toxicol 17: 449,456, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/tox.10078 [source] Does the Giant Wood Spider Nephila pilipes Respond to Prey Variation by Altering Web or Silk Properties?ETHOLOGY, Issue 4 2007I-Min Tso Recent studies demonstrated that orb-weaving spiders may alter web architectures, the amount of silk in webs, or the protein composition of silks in response to variation in amount or type of prey. In this study, we conducted food manipulations to examine three mechanisms by which orb-weaving spiders may adjust the performance of webs to variation in prey by altering the architectures of webs, making structural changes to the diameters of silk threads, and manipulating the material properties or amino acid composition of silk fibers. We fed Nephila pilipes two different types of prey, crickets or flies, and then compared orb structure and the chemical and physical properties of major ampullate (MA) silk between groups. Prey type did not affect orb structures in N. pilipes, except for mesh size. However, MA silk diameter and the stiffness of orbs constructed by spiders fed crickets were significantly greater than for the fly group. MA fibers forcibly silked from N. pilipes fed crickets was significantly thicker, but less stiff, than silk from spiders fed flies. Spiders in the cricket treatment also produced MA silk with slightly, but statistically significantly, more serine than silk from spiders in the fly treatment. Percentages of other major amino acids (proline, glycine, and glutamine) did not differ between treatments. This study demonstrated that orb-weaving spiders can simultaneously alter some structural and material properties of MA silk, as well as the physical characteristics of webs, in response to different types of prey. [source] HAVE MALE AND FEMALE GENITALIA COEVOLVED?EVOLUTION, Issue 9 2005A PHYLOGENETIC ANALYSIS OF GENITALIC MORPHOLOGY AND SEXUAL SIZE DIMORPHISM IN WEB-BUILDING SPIDERS (ARANEAE: ARANEOIDEA) Abstract Sexual size dimorphism (SSD) can strongly influence the evolution of reproductive strategies and life history. If SSD is extreme, and other characters (e.g., genitalic size) also increase with size, then functional conflicts may arise between the sexes. Spiders offer an excellent opportunity to investigate this issue because of their wide range of SSD. By using modern phylogenetic methods with 16 species of orb-weaving spiders, we provide strong evidence for the "positive genitalic divergence" model, implying that sexual genitalic dimorphism (SGD) increases as SSD increases. This pattern is supported by an evolutionary mismatch between the absolute sizes of male and female genitalia across species. Indeed, our findings reveal a dramatic reversal from male genitalia that are up to 87X larger than female genitalia in size-monomorphic species to female genitalia that are up to 2.8X larger in extremely size-dimorphic species. We infer that divergence in SGD could limit SSD both in spiders, and potentially in other taxa as well. Further, male and female body size, as well as male and female genitalia size, are decoupled evolutionarily. Finally, we show a negative scaling (hypoallometry) of male and female genitalic morphology within sexes. Evolutionary forces specific to each sex, such as larger female size (increased fecundity) or smaller male size (enhanced mate-searching ability), may be balanced by stabilizing selection on relative genitalic size. [source] Guanine-Based Biogenic Photonic-Crystal Arrays in Fish and SpidersADVANCED FUNCTIONAL MATERIALS, Issue 2 2010Avital Levy-Lior Abstract Biological photonic systems composed of anhydrous guanine crystals evolved separately in several taxonomic groups. Here, two such systems found in fish and spiders, both of which make use of anhydrous guanine crystal plates to produce structural colors, are examined. Measurements of the photonic-crystal structures using cryo-SEM show that the crystal plates in both fish skin and spider integument are ,20-nm thick. The reflective unit in the fish comprises stacks of single plates alternating with ,230-nm-thick cytoplasm layers. In the spiders the plates are formed as doublet crystals, cemented by 30-nm layers of amorphous guanine, and are stacked with ,200,nm of cytoplasm between crystal doublets. They achieve light reflective properties through the control of crystal morphology and stack dimensions, reaching similar efficiencies of light reflectivity in both fish skin and spider integument. The structure of guanine plates in spiders are compared with the more common situation in which guanine occurs in the form of relatively unorganized prismatic crystals, yielding a matt white coloration. [source] The effects of morphology and substrate diameter on climbing and locomotor performance in male spidersFUNCTIONAL ECOLOGY, Issue 2 2010John Prenter Summary 1.,Spiders are the most sexually size dimorphic terrestrial animals and the evolution of this dimorphism is controversial. Patterns of sexual size dimorphism (SSD) in spiders have been related to individual performance and size. In 2002 Moya-Laraño, Halaj & Wise proposed the ,gravity hypothesis' to explain patterns of sexual size dimorphism in spiders whereby species building webs high in the vegetation are predicted to show greater SSD than those that build lower down. They advocated an advantage in climbing speed in smaller males searching for females in high places. The gravity hypothesis predicts a negative relationship between male size and climbing speed. In 2007 Brandt & Andrade questioned this interpretation and proposed that the pattern of SSD in spiders is better explained by an advantage for larger males of low-dwelling species to run faster along the ground. 2.,We induced male spiders to run a standard distance up vertical poles of different diameters to examine the predicted relationship between size and climbing speed. We tested two species of extremely size-dimorphic orb-web spiders, Argiope keyserlingi and Nephila plumipes, that differ in the height at which females tend to build webs, and one species of jumping spider, Jacksonoides queenslandica, with low levels of size dimorphism. We also examined morphological determinants of horizontal motility by inducing males to run along a raceway. 3.,Substrate diameter was consistently found to influence climbing performance. In N. plumipes, climbing speed was slowest on the widest diameter substrate. In A. keyserlingi, size-adjusted leg length and substrate diameter interacted to determine climbing speed, while in J. queenslandica, there was an interaction between body size and substrate diameter on climbing speed. In the effect of substrate diameter, we have identified a potential bias in previous tests of the gravity hypothesis. 4.,Our results do not support the prediction of the gravity hypothesis. There was no evidence of a negative relationship between body size and climbing speed in the two orb-web species with high levels of SSD. Our results are also not consistent with a recent modification of the gravity hypothesis that suggests a curvilinear relationship between climbing speed and size. 5.,Body size was positively associated with maximum running speed only in the cursorial hunter J. queenslandica. For this spider, results are more consistent with Brandt & Andrade's explanation for variation in SSD in spiders, that larger males are selected for superior running ability in low-dwelling species, rather than selection for smaller size for climbing to females in high-dwelling species. [source] Assessment of rampant genitalic variation in the spider genus Homalonychus (Araneae, Homalonychidae)INVERTEBRATE BIOLOGY, Issue 2 2009Sarah C. Crews Abstract. Animal genitalia are often complex and thought to vary little within species but differ between closely related species making them useful as primary characters in species diagnosis. Spiders are no exception, with nearly all of the 40,462 (at the time of this writing) described species differentiated by genitalic characteristics. However, in some cases, the genitalia of putative species are not uniform, but rather vary within species. When intraspecific variation overlaps interspecific variation, it can be difficult (if not impossible) to place a name on a specimen. The quantification of shape variation in genitalia has not often been attempted, probably because until recently it was not a methodologically and computationally simple process. In the two currently recognized species of the spider genus Homalonychus, genitalic variation is rampant in both male and female structures, with some parts of the genitalia (e.g., the retrolateral tibial apophysis) differing in each specimen examined. In this study, geometric morphometric analysis employing landmark data is used to quantify both intra- and interspecific variation in this genus. The large amount of variation is condensed into two or three groups depending on the structures examined, and these groups correspond to either the two species or to previously established mitochondrial DNA clades within one of the species. The results also show that analyses of female structures do not separate the groups as readily as the analyses of the male structures. The large amount of variation present in some structures is not correlated with geography or population genetic structure. [source] Nutritional value of cannibalism and the role of starvation and nutrient imbalance for cannibalistic tendencies in a generalist predatorJOURNAL OF ANIMAL ECOLOGY, Issue 1 2006DAVID MAYNTZ Summary 1Cannibalism is considered an adaptive foraging strategy for animals of various trophic positions, including carnivores. However, previous studies on wolf spiders have questioned the high nutritional value of cannibalism. We therefore analysed two different aspects of nutritional quality of conspecifics in the wolf spider Pardosa prativaga: their value for survival, growth and development; and the growth efficiency of feeding on conspecifics. We also measured the propensity for cannibalistic attacks and the consumption rate of conspecifics in an experiment where hunger level and nutrient balance were manipulated. In all experiments, cannibalism was compared with predation on fruit flies as control prey. 2The growth experiment gave ambiguous results regarding the nutritional quality of conspecifics. Spiders on pure cannibalistic diets split into two distinct groups, one performing much better and the other much worse than spiders on fruit fly diets. We discuss the possibility that the population is dimorphic in its cannibalistic propensity, with the latter group of individuals showing a high level of inhibition against cannibalistic attacks in spite of a high nutritional value of cannibalism. 3The food utilization experiment confirmed the high nutritional quality of conspecifics, as cannibalistic spiders had the same growth rate as spiders fed insect prey in spite of a much lower consumption rate. 4Inhibition against cannibalistic attacks was demonstrated in medium-sized juveniles: only half of the spiders attacked a prescribed victim of 50% the size of their opponents, and the latency for those that did attack was more than half an hour, compared with a few minutes for spiders fed fruit flies. 5Nutrient-imbalanced spiders utilized an alternative insect diet less efficiently than balanced spiders, whereas no difference was present in efficiency of utilizing conspecifics. This result indicates that spiders can remedy at least part of a nutrient imbalance through cannibalism. 6As spiders can escape nutritional imbalance as well as restore energy reserves through cannibalism, we predicted both nutrient imbalance and hunger to stimulate cannibalism. This prediction was confirmed only with respect to hunger. Nutrient-imbalanced spiders had reduced cannibalistic consumption, perhaps due to lowered predatory aggressiveness as a result of bad condition. [source] The effects of plant structure on the spatial and microspatial distribution of a bromeliad-living jumping spider (Salticidae)JOURNAL OF ANIMAL ECOLOGY, Issue 1 2005GUSTAVO Q. ROMERO Summary 1In several regions of South America, the neotropical jumping spider Psecas chapoda inhabits and reproduces strictly on the bromeliad Bromelia balansae. Previous studies reported that this spider is more frequent on bromeliads in grasslands than on those growing in forests, and on larger plants, but only when the bromeliads are without inflorescence. Upon blooming, B. balansae fold their leaves back, thereby changing the plant architecture from a tri-dimensional to a bi-dimensional flattened shape, and our hypothesis is that this alteration affects the spider's habitat-selection decisions. 2In the present study, we examined experimentally the effects of inflorescence, plant size and blockade of the axil of the leaves (spider shelters) of forest bromeliads on the colonization of a bromeliad by P. chapoda. By using sticky traps, we also compared prey availability in grassland and forest. 3Plants with simulated inflorescence were colonized at a lower frequency than those without inflorescence simulation. Grassland bromeliads in which the rosettes were blocked with dry leaves were colonized less frequently than open bromeliads, whereas forest bromeliads from which dry leaves had been removed were not colonized. Spiders generally abandoned bromeliads in which three-quarters of the length of the leaves had been removed, although females with eggsacs remained on these plants. Prey availability (biomass and number) was up to 18 fold higher in the grassland than in the forest. These results suggest that microhabitat structure and prey availability shape the spatial distribution of P. chapoda populations. 4Our findings suggest that Psecas chapoda can evaluate, in fine detail, the physical state of its microhabitat, and this unusual spider,plant association is readily destabilized by changes in the microhabitat (i.e., it is strictly dependent on the size and morphology of the host plant). This study is one of the few to report a strict association between a spider species and its host plant, and also one of the few to examine the effects of habitat and microhabitat structure on the spatial distribution of active hunters on plants. [source] Aged pesticide residues are detrimental to agrobiont spiders (Araneae)JOURNAL OF APPLIED ENTOMOLOGY, Issue 8 2008S. Pekár Abstract Spiders are among the most abundant arthropods in agroecosystems, playing an important role as natural enemies of various pests. In this study we evaluated residual activity of selected pesticides on the mortality and behaviour of four spider species (Dictyna uncinata, Pardosa palustris, Philodromus cespitum and Theridion impressum). We used three pesticides: a herbicide Command (clomazone), and insecticides Decis (deltamethrin) and Nurelle (chlorpyrifos and cypermethrin). Mortality was recorded after exposure of spiders to fresh (2-h), 5, 10, 15 and 20-day-old residues. For each residue mortality was evaluated after 24,72 h. Residual effect differed between preparations and, in some cases, between spiders. All of the Nurelle residues (fresh to 20-day-old) caused 100% mortality in all spider species. Residues of Command were rather harmless (causing <20% mortality) to all spider species as the herbicide activity declined with age. Residues of Decis had species-specific effects as the mortality varied between 0 and 90%. In Dictyna the mortality gradually declined with the age of residues, while in Pardosa the mortality increased. In Philodromus and Theridion the mortality declined up to 10-day-old residues and then increased so that 20-day-old residues caused almost as high mortality as the new ones. Exposure to pesticide residues immediately affected the movement of Pardosa spiders. Residues of Decis and Nurelle decreased spider locomotion, while those of Command increased locomotion in comparison with the control. In another experiment, we studied repellence of fresh pesticide residues to Pardosa spiders. In comparison with the control, spiders stayed a similar time on the surface treated with Command, but four times less on Decis and nine times less on Nurelle-treated surfaces, respectively. In conclusion, aged insecticide residues possess a high activity and can cause long-term decline in the abundance and prolonged behavioural disturbance of spiders in agroecosystems. [source] Contrasting responses of arable spiders to the landscape matrix at different spatial scalesJOURNAL OF BIOGEOGRAPHY, Issue 1 2008Martin H. Schmidt Abstract Aim, Animal communities can be influenced by the composition of the surrounding landscape through immigration. Depending on habitat preferences, however, the effect of the landscape matrix can be positive or negative and can vary with scale. We tested this idea with arable spiders and tried to infer dispersal distances from relationships between local density and landscape composition at different spatial scales. Location, Thirty-eight landscapes around the cities of Göttingen and Giessen, Germany. Methods, Spiders were captured with pitfall traps in one field of winter wheat in each landscape. Landscape composition around the fields was characterized at 11 scales from 95 m to 3 km radius by land-use mapping and subsequent GIS analysis. Correlation tests were performed between landscape composition and local densities or species richness. Results, In both study regions, local species richness was enhanced by non-crop habitats on a landscape scale. The overall densities of wolf spiders (Lycosidae), long-jawed spiders (Tetragnathidae), crab spiders (Thomisidae), and dwarf sheet spiders (Hahniidae) increased significantly in landscapes with high percentages of non-crop habitats. Out of the 40 species tested, 19 responded positively to the percentage of non-crop habitats in the surrounding landscape, and five responded negatively. Depending on the species, the spatial scales with the highest explanatory power ranged from 95 m to 3 km radius around the study fields, potentially reflecting dispersal distances. Main conclusions, Arable spider species showed contrasting responses to the landscape context with respect both to the direction and to the spatial scale of the relationship. The variation in landscape requirements among species ensures high spider densities in a wide range of situations, which contributes to ecosystem resilience. However, species richness of arable spiders depends on heterogeneous landscapes with high percentages of non-crop habitats. [source] Spiders as potential indicators of elephant-induced habitat changes in endemic sand forest, Maputaland, South AfricaAFRICAN JOURNAL OF ECOLOGY, Issue 2 2010Charles R. Haddad Abstract Elephant impacts on spider assemblages, and the potential use of spiders as indicators of habitat changes was assessed in central Maputaland, South Africa. Three habitats, namely undisturbed sand forest, elephant disturbed sand forest and mixed woodland, were sampled. To ensure a thorough representation of all spider guilds, spiders were collected by tree beating, sweep netting, active searching, leaf litter sifting and pitfall traps. In total, 2808 individual spiders, representing 36 families, 144 determined genera and 251 species were collected. Spider abundance was highest in the undisturbed sand forest (n = 1129, S = 179), followed by elephant disturbed sand forest (n = 1006, S = 165) and mixed woodland (n = 673, S = 171). Assemblages of the two sand forests were more similar than to the mixed woodland assemblage. Active hunting species were indicators of the more open vegetation of elephant disturbed sand forest (six active hunters, no web-builders) and mixed woodland (ten active hunters, one web-builder), whereas web-builders are indicators of the dense, complex vegetation structure of undisturbed sand forest (six web-builders, three active hunters). Elephant-induced changes to the vegetation structure in this high diversity, high endemism region result in changes in the composition of spider assemblages, and may need to be mitigated by management intervention. Résumé L'impact des éléphants sur les assemblages d'araignées, et l'utilisation éventuelle des araignées comme indicateurs de changements des habitats, ont étéévalués dans le centre du Maputaland, en Afrique du Sud. Trois habitats ont étééchantillonnés, à savoir la forêt sableuse intacte, la forêt sableuse perturbée par des éléphants et la forêt mixte. Pour garantir une représentation complète de toutes les guildes d'araignées, on a récolté des araignées en frappant sur les arbres, en agitant des filets, en pratiquant une recherche active, en tamisant la litière de feuilles, et avec des pièges. Au total, on a récolté 2 808 araignées; représentant 36 familles, 144 genres déterminés et 251 espèces. L'abondance d'araignées était la plus grande dans la forêt sableuse non perturbée (n = 1129, S = 179), suivie par la forêt sableuse perturbée par les éléphants (n = 1006, S = 165), puis par la forêt mixte (n = 673, S = 171). Les assemblages des deux forêts sableuses étaient plus semblables entre eux qu'avec celui de la forêt mixte. Les espèces d'araignées qui chassent activement étaient des indicateurs de la végétation plus ouverte de la forêt perturbée par les éléphants (six chasseurs actifs, aucun constructeur de toile) et de la forêt mixte (dix chasseurs actifs, un constructeur de toile), alors que les constructeurs de toile étaient des indicateurs de la structure dense et complexe de la végétation de la forêt sableuse intacte (six constructeurs de toile, trois chasseurs actifs). Les éléphants induisaient des changements dans la structure de la végétation de cette région à la diversitéélevée et d'un fort endémisme, ce qui entraînait des modifications de la composition des assemblages d'araignées. Cela pourrait devoir être atténué par une intervention de la gestion. [source] Spiders (Araneae) associated with downed woody material in a deciduous forest in central Alberta, CanadaAGRICULTURAL AND FOREST ENTOMOLOGY, Issue 4 2001Christopher M. Buddle Abstract 1,Spiders (Araneae) were collected on and near downed woody material (DWM) in a Populus -dominated forest to determine if spiders utilize wood surfaces, and to ascertain the importance of DWM habitat and wood elevation for spider assemblages. 2,Over 10 000 spiders representing 100 species were collected. Although more spiders were collected on the forest floor, spider diversity was higher in traps located on wood surfaces than on the forest floor, and 11 species were collected more frequently on wood surfaces. 3,Spiders utilized DWM at different stages in their development. Female Pardosa mackenziana (Keyserling) (Lycosidae) carrying egg sacs were caught most often on the surface of DWM, possibly to sun their egg sacs. Additionally, the proportion of immature spiders was higher on the wood surface than on the forest floor. 4,Spiders collected on logs with and without bark were compared to assemblages collected on telephone poles to assess what features of DWM habitat may be important. Web-building species were seldom collected on telephone poles, suggesting that they depend on the greater habitat complexity provided by DWM. In contrast, hunting spiders did not distinguish between telephone poles and logs. 5,Fewer spiders and a less diverse fauna utilized elevated compared to ground-level wood. Additionally, Detrended Correspondence Analysis revealed that the spider community from elevated wood was distinguishable from the spider community from ground-level wood, and from the forest floor spider community. [source] Silk feeding as an alternative foraging tactic in a kleptoparasitic spider under seasonally changing environmentsJOURNAL OF ZOOLOGY, Issue 3 2004Tadashi Miyashita Abstract Spiders of the genus Argyrodes are kleptoparasites that steal prey from other web spiders. Recent studies have shown that in addition to stealing prey, they occasionally eat the silk of the host spider webs. How Argyrodes alters the two foraging tactics in the field is still unknown. The foraging behaviour of Argyrodes flavescens was observed in the south-western part of Japan where prey availability changes greatly with season. Silk-eating behaviour was commonly observed when insect prey availability on host webs was low, but when prey was abundant, only prey-stealing behaviour was observed. Spiders spent more time feeding on silk than on prey when prey was scarce. Moreover, in the season when most individuals fed on silk, only a small portion of individuals consumed prey. These results suggest that silk eating is an important alternative foraging tactic under seasonally changing environments. [source] State-dependent prey type preferences of a kleptoparasitic spider Argyrodes flavescens (Araneae: Theridiidae)JOURNAL OF ZOOLOGY, Issue 3 2003Teck Hui Koh Spiders from the theridiid genus Argyrodes exhibit considerable variation in foraging tactics. However, little is known about the conditions under which Argyrodes spiders switch foraging tactics. Argyrodes flavescens (Pickard-Cambridge) is commonly found in the webs of another spider Nephila pilipes (Fabricius) in Singapore. In this study, a series of prey-choice tests were conducted for A. flavescens, both in the presence and absence of N. pilipes, to investigate the state-dependent prey type preference of A. flavescens. It was found that, in the absence of N. pilipes, well-fed A. flavescens took houseflies more than fruit flies, but starved A. flavescens took more fruit flies than houseflies. Whether N. pilipes spiders were present or absent, both well-fed and starved A. flavescens preferred living prey and rarely took wrapped prey of any kind. When well fed, A. flavescens rarely took mealworms. However, when starved, A. flavescens tended to take freshly captured prey, and also tended to feed together with N. pilipes on a housefly or mealworm captured by N. pilipes. Whether A. flavescens were absent or present, both well-fed and starved N. pilipes took mealworm larvae more often than they took houseflies, and they never attacked fruit flies. This is the first study to show that Argyrodes spiders alter their foraging tactics depending on hunger level, prey type, or the presence of the host. In doing so, Argyrodes spiders may maximize their energy gain and minimize predation risk in different circumstances. [source] Spiders in Upper Cretaceous Amber from New Jersey (Arthropoda: Araneae)PALAEONTOLOGY, Issue 4 2002David Penney The oldest described fossils of the extant spider families Segestriidae, Oonopidae, Oecobiidae, Dictynidae and Linyphiidae, previously known from the Tertiary, are presented from Upper Cretaceous amber of New Jersey. The third and oldest known specimen of the fossil spider family Lagonomegopidae is also described and provides further palaeontological evidence of a common Laurasian fauna. The extant genera Segestria and Oecobius are taken back a further 52 and 69,74 myr respectively in the fossil record. These fossils predict the presence of the Caponiidae, Tetrablemmidae, Orsolobidae, Dysderidae, Hersiliidae, Eresidae, Pimoidae, Scytodoidea s.l., cyatholipoids, theridioids and symphytognathoids in the Cretaceous. They also extend the known geological range of extant spider families through and beyond the end,Cretaceous extinction. This event, which affected numerous marine and some terrestrial organisms, probably had little effect on the Araneae. [source] Can ant-eating Zodarion spiders (Araneae: Zodariidae) develop on a diet optimal for euryphagous arthropod predators?PHYSIOLOGICAL ENTOMOLOGY, Issue 2 2009STANO PEKÁR Abstract Little attention is paid to the behavioural and physiological adaptations of ant-eating predators. It is expected that there should be a strong selection for traits related to prey handling, leading to the evolution of morphological, behavioural and nutritional adaptations. Such adaptations may then entail trade-offs in handling and utilization of alternative prey. To investigate behavioural as well as nutritional adaptations and the occurrence of the corresponding trade-offs in two ant-eating spiders of the genus Zodarion [Zodarion atlanticum Pekár & Cardoso and Zodarion germanicum (C. L. Koch)], spiders are reared on two diets: ants (i.e. their preferred prey) and fruit flies (i.e. an alternative prey that is nutritionally optimal for euryphagous spiders). Food consumption is observed and several fitness-related life-history parameters are measured. Although spiders readily accept ants, more than one-third of 35 spiders refuse to consume fruit flies and starve. Furthermore, severe hunger does not induce these individuals to accept fruit flies. Starving spiders die before moulting to the second stadium. Spiders that eat fruit flies increase only little and slowly in weight, and all of these die during the first two stadia. By contrast, spiders on an ant diet increase dramatically in weight, and develop up to the fourth stadium. These data indicate that fruit flies are not suitable for Zodarion, supporting the hypothesis that there are behavioural and nutritional trade-offs. Taking into account the results of previous studies, it is suggested that nutritional trade-offs are generally important for stenophagous spiders. [source] Spider sex pheromones: emission, reception, structures, and functionsBIOLOGICAL REVIEWS, Issue 1 2007A. C. Gaskett Abstract Spiders and their mating systems are useful study subjects with which to investigate questions of widespread interest about sexual selection, pre- and post-copulatory mate choice, sperm competition, mating strategies, and sexual conflict. Conclusions drawn from such studies are broadly applicable to a range of taxa, but rely on accurate understanding of spider sexual interactions. Extensive behavioural experimentation demonstrates the presence of sex pheromones in many spider species, and recent major advances in the identification of spider sex pheromones merit review. Synthesised here are the emission, transmission, structures, and functions of spider sex pheromones, with emphasis on the crucial and dynamic role of sex pheromones in female and male mating strategies generally. Techniques for behavioural, chemical and electrophysiological study are summarised, and I aim to provide guidelines for incorporating sex pheromones into future studies of spider mating. In the spiders, pheromones are generally emitted by females and received by males, but this pattern is not universal. Female spiders emit cuticular and/or silk-based sex pheromones, which can be airborne or received via contact with chemoreceptors on male pedipalps. Airborne pheromones primarily attract males or elicit male searching behaviour. Contact pheromones stimulate male courtship behaviour and provide specific information about the emitter's identity. Male spiders are generally choosy and are often most attracted to adult virgin females and juvenile females prior to their final moult. This suggests the first male to mate with a female has significant advantages, perhaps due to sperm priority patterns, or mated female disinterest. Both sexes may attempt to control female pheromone emission, and thus dictate the frequency and timing of female mating, reflecting the potentially different costs of female signalling and/or polyandry to both sexes. Spider sex pheromones are likely to be lipids or lipid soluble, may be closely related to primary metabolites, and are not necessarily species specific, although they can still assist with species recognition. Newer electrophysiological techniques coupled with chemical analyses assist with the identification of sex pheromone compounds. This provides opportunities for more targeted behavioural experimentation, perhaps with synthetic pheromones, and for theorising about the biosynthesis and evolution of chemical signals generally. Given the intriguing biology of spiders, and the critical role of chemical signals for spiders and many other animal taxa, a deeper understanding of spider sex pheromones should prove productive. [source] Foliage Density of Branches and Distribution of Plant-Dwelling Spiders,BIOTROPICA, Issue 3 2005Andréa Lúcia Teixeira De Souza ABSTRACT We compared the abundance of foliage-living spiders among seven widespread plant species comprising a gradient of levels of structural complexity in a tropical savannah-like region in southeastern Brazil. Spider abundance among plant species was positively related to the foliage density of their branches. A field experiment using artificial branches was carried out to isolate foliage density effects on spider abundance, thus controlling both biomass and texture effects. Artificial branches were attached to branches of three plant species with similar foliage density, Baccharis dracunculifolia, Diplusodon virgatus, and Microlicia fasciculata. Two treatments were set up: artificial branches with higher foliage density attracted more spiders than those with lower foliage density. The guild structure of hunting spiders was compared among vegetative branches of three plant species with different levels of foliage density: B. dracunculifolia, D. virgatus, and Bidens gardneri. Stalker, and ambusher spiders were more abundant on branches of B. dracunculifolia, which had the highest foliage density. Foliage-runners constituted the dominant guild on D. virgatus and B. gardneri, which have lower foliage density branches. Our results suggest that branch architecture is the most important factor determining the abundance of plant-dwelling spiders in the study area independently of branch biomass, leaf surface area or texture. RESUMO A abundância de aranhas foi comparada entre sete espécies de plantas, que formam um gradiente de níveis de complexidade estrutural, descrito através do número de folhas por unidade de volume do ramo, numa região de cerrado no sudeste do Brasil. A abundância de aranhas entre as espécies de plantas foi positivamente relacionada com a densidade de folhas de seus ramos. Um experimento de campo, usando ramos artificiais, foi conduzido para isolar o efeito da densidade de folhas dos efeitos de biomassa. Ramos artificiais foram amarrados a ramos de três especies de plantas com densidade foliar semelhante, Baccharis dracunculifolia, Diplusodon virgatus and Microlicia fasciculata. Dois tratamentos foram usados, ramos artificiais com alta densidade de folhas atraíram mais aranhas do que os com baixa densidade de folhas. A distribuição de guildas de aranhas errantes foi comparada entre ramos de três espécies de plantas com diferentes níveis de densidade de folhas, B. dracunculifolia, D. virgatus e Bidens gardneri. Aranhas saltadoras (Oxyopidae e Salticidae) e de tocaia (Thomisidae) foram mais abundantes nos ramos de B. dracunculifolia, cujos ramos possuíam uma maior densidade de folhas. Aranhas caçadoras noturnas foi a guilda dominante em D. virgatus e B. gardneri. Nossos resultados sugerem que a arquitetura de ramos pode ser o fator mais importante que determina a abundância de aranhas que habitam plantas, independentemente da biomassa, área superficial de folhas e textura dos ramos. [source] Spatial Distribution Patterns of Jumping Spiders Associated with Terrestrial BromeliadsBIOTROPICA, Issue 4 2004Gustavo Q. Romero ABSTRACT The jumping spiders Eustiromastix native, Psecas sumptuosus, and Uspachus sp. n. (Salticidae) live on terrestrial bro-meliads in areas with different phytophysiognomies in southeastern and northeastern Brazil. To understand these spider,plant interactions, we investigated if (1) these spiders were associated specifically with bromeliads, (2) the spiders utilized particular bromeliad species, and (3) plant size and density of bromeliads affected spider distribution. The jumping spiders were not found outside bromeliads, indicating a strict spider,plant association. Eustiromastix and Uspachus occupied bromeliads in open areas, whereas Psecas was found on forest bromeliads. Eustiromastix occurred at a higher frequency on larger bromeliads and in patches with higher bromeliad density. This is one of the few studies to demonstrate specific relationships between jumping spiders and a particular plant type. RESUMO As aranhas saltadoras Eustiromastix native, Psecas sumptuosus e Uspachus sp. n. (Salticidae) vivem sobre bromélias terrestres em áreas com diferentes fitofisionomias no sudeste e nordeste do Brasil. Para compreender estas interaçóes aranha-planta, nós investigamos se (1) estas aranhas estavam associadas especificamente a bromélias, (2) as aranhas utilizam espécies particulares de bromélias e (3) tamanho e densidade das bromélias afetam a distribuiçáo das aranhas. As aranhas saltadoras não foram encontradas fora das bromélias, indicando uma associaçáo estrita entre aranha e planta. Eustiromastix e Uspachus ocuparam bromelias em areas abertas enquanto Psecas foi encontrada em bromélias de floresta. Eustiromastix ocorreu em maior freqüéncia sobre bromélias maiores e em manchas com maior densidade de bromélias. Este estudo é um dos poucos a demonstrar relaço,es especificas entre aranhas saltadoras e um tipo particular de planta. [source] Effects of an organophosphorous insecticide on survival, fecundity, and development of Hylyphantes graminicola (Sundevall) (Araneae: Linyphiidae)ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 11 2006Lingling Deng Abstract The effects of an organophosphorous insecticide, methamidophos, on fecundity and development of the spider Hylyphantes graminicola (Sundevall) (Araneae: Linyphiidae) were assessed under laboratory conditions. Susceptibility of adults of both sexes to the insecticide and its influence on fecundity of females and development of offspring were investigated. At 48 h after topical application in adults, the median lethal dose (LD50) and 10% lethal dose (LD10) were 0.35 and 0.12 ,g/spider, respectively, for males and 0.52 and 0.16 ,g/spider, respectively, for females. Methamidophos had detrimental effects on fecundity of females; number of eggs per clutch, total egg mass, and clutch size decreased significantly. The hatching rate of eggs from LD10-treated females was slightly higher than the rate in the controls, but the hatching rate of eggs from LD50-treated females was lower than the rate in the controls. However, no significant differences were observed in hatching time and development time across treatments. Development time of spiderlings from LD50-treated females was significantly longer than the time in the controls, and body sizes of the first spiderlings from insecticide-treated females were larger than those in the controls. However, matured offspring were smaller than those in the controls. It was concluded that methamidophos has long-term effects on H. graminicola, and that this may affect the development of spider populations in the field. [source] | |||||||||||||||||||||||||||||||||||||||||||