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Wolf Spiders (wolf + spider)

Distribution by Scientific Domains

Life Sciences	53%

Selected Abstracts

Sublethal responses of wolf spiders (Lycosidae) to organophosphorous insecticides

ENVIRONMENTAL TOXICOLOGY, Issue 5 2002
S. 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]

Interdemic variation of cannibalism in a wolf spider (Pardosa monticola) inhabiting different habitat types

ECOLOGICAL ENTOMOLOGY, Issue 2 2006
Jeroen Vanden Borre
Abstract., 1.,Cannibalism was investigated in the wolf spider Pardosa monticola (Clerck) using spiders collected from four populations with varying densities, inhabiting two different coastal dune habitat types. Sampled individuals were paired randomly and tested immediately for their cannibalism propensity. 2.,The occurrence of cannibalism was found to be influenced by the size (cephalothorax width) of both the smaller and the larger spider of a pair. Larger size differences enhanced cannibalism. 3.,Cannibalism rates were not significantly different in spiders from high-density compared with low-density populations. Cannibalism rates showed, however, large variability between habitat types, with higher rates in spiders from dune grasslands than from dune slacks. This is suggested to result from differences in prey availability throughout the growing season between both habitat types. 4.,Different size classes of spiders did not use different microhabitats, indicating that microhabitat segregation as a cannibalism-avoidance behaviour is absent in this species. [source]

Effects of hunger level and nutrient balance on survival and acetylcholinesterase activity of dimethoate exposed wolf spiders

ENTOMOLOGIA EXPERIMENTALIS ET APPLICATA, Issue 3 2002
Lars-Flemming Pedersen
Abstract The influence of two nutritional factors (food quantity and quality) on the responses of a wolf spider, Pardosa prativaga (L.K.), to a high dose of the insecticide dimethoate, was investigated in a fully factorial experimental design. Spider groups with different (good and bad) nutrient balance were created by feeding them fruit flies of either high or low nutrient content for 28 days. Both groups were then split into satiated and 14 days starved subgroups. Each of these was further divided into insecticide treated and control halves. Survivorship and acetylcholinesterase (AChE) activity measured on the survivors were used as response variables. Survivorship after topical dimethoate exposure (LD50; 48 h) was influenced by spider body weight, nutrient balance, and starvation. Furthermore, AChE activity was significantly inhibited by dimethoate exposure. A significant interaction between nutrient balance, starvation, and dimethoate exposure revealed synergistic effects of starvation and nutrient imbalance on AChE inhibition by dimethoate in surviving spiders. These results show that the tolerance of non-target arthropods to dimethoate may vary depending on the nutritional history of the animal. [source]

Sublethal responses of wolf spiders (Lycosidae) to organophosphorous insecticides

Effects of Predation Risk on Vertical Habitat Use and Foraging of Pardosa milvina

ETHOLOGY, Issue 12 2006
Hillary C. Folz
Animals face the risk of predation while engaging in regular activities, such as foraging, mate-seeking, and reproducing. In order to avoid predation, prey can modify behavior to prevent capture. Pardosa milvina may climb in response to chemotactile cues of Hogna helluo, a larger cooccurring wolf spider, to avoid predation. The purpose of this study was to test the effects of the location of predator cues on the climbing response of P. milvina and to test how this antipredator behavior affected foraging success. In experimental arenas, when cues were on the bottom of the containers, P. milvina moved upward, and when cues were on the walls, individuals moved downward. These results suggest that P. milvina respond to H. helluo cues with general avoidance and do not automatically climb in response to the cues. As H. helluo spend most of their time on the ground, P. milvina may avoid predation by spending more time climbing in areas with H. helluo cues. The presence of predator cues significantly decreased foraging by P. milvina. But within the predator cue treatments, climbing ability had no effect on foraging, possibly due to the short height of the feeding arenas. Future studies are needed to determine if climbing by P. milvina in response to cues of H. helluo has direct and indirect negative effects on herbivores in the field. [source]

Development, growth, and egg production of Ageneotettix deorum (Orthoptera: Acrididae) in response to spider predation risk and elevated resource quality

ECOLOGICAL ENTOMOLOGY, Issue 1 2004
Bradford.
Abstract., 1.,Predation risk to insects is often size- or stage-selective and usually decreases as prey grow. Any factor, such as food quality, that accelerates developmental and growth rates is likely to reduce the period over which prey are susceptible to size-dependent predation. 2.,Using field experiments, several hypotheses that assess growth, development, and egg production rates of the rangeland grasshopper Ageneotettix deorum (Scudder) were tested in response to combinations of food quality and predation risk from wolf spiders to investigate performance variation manifested through a behaviourally mediated path affecting food ingestion rates. 3.,Grasshoppers with nutritionally superior food completed development , 8,18% faster and grew 15,45% larger in the absence of spiders, in comparison with those subjected to low quality food exposed to spider predators. Growth and development did not differ for grasshoppers feeding on high quality food when predators were present in comparison with lower quality food unimpeded by predators. Responses indicated a compensatory relationship between resource quality and predation risk. 4.,Surviving grasshoppers produced fewer eggs compared with individuals not exposed to spiders. Because no differences were found in daily egg production rate regardless of predation treatment, lower egg production was attributed to delayed age of first reproduction. Results compare favourably with responses observed in natural populations. 5.,Risk of predation from spiders greatly reduced growth, development, and ultimately egg production. Increased food quality counteracts the impact of predation risk on grasshoppers through compensatory responses, suggesting that bottom-up factors mediate effects of spiders. [source]

Effects of hunger level and nutrient balance on survival and acetylcholinesterase activity of dimethoate exposed wolf spiders

Sublethal responses of wolf spiders (Lycosidae) to organophosphorous insecticides

Nutritional value of cannibalism and the role of starvation and nutrient imbalance for cannibalistic tendencies in a generalist predator

JOURNAL OF ANIMAL ECOLOGY, Issue 1 2006
DAVID 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]

Contrasting responses of arable spiders to the landscape matrix at different spatial scales

JOURNAL OF BIOGEOGRAPHY, Issue 1 2008
Martin 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]

Generalist predators in organically and conventionally managed grass-clover fields: implications for conservation biological control

ANNALS OF APPLIED BIOLOGY, Issue 2 2008
K Birkhofer
Abstract Organically managed agroecosystems rely in part on biological control to prevent pest outbreaks. Generalist predators (Araneae, Carabidae and Staphylinidae) are a major component of the natural enemy community in agroecosystems. We assessed the seasonal dynamics of major generalist predator groups in conventionally and organically managed grass,clover fields that primarily differed by fertilisation strategy. We further established an experiment, manipulating the abundant wolf spider genus Pardosa, to identify the importance of these predators for herbivore suppression in the same system and growth period. Organic management significantly enhanced ground-active spider numbers early and late in the growing season, with potentially positive effects of plant cover and non-pest decomposer prey. However, enhancing spider numbers in the field experiment did not improve biological control in organically managed grass,clover fields. Similar to the survey results, reduced densities of Pardosa had no short-term effect on any prey taxa; however, spider guild structure changed in response to Pardosa manipulation. In the presence of fewer Pardosa, other ground-running spiders were more abundant; therefore, their impact on herbivore numbers may have been elevated, possibly cancelling increases in herbivore numbers because of reduced predation by Pardosa. Our results indicate positive effects of organic farming on spider activity density; however, our survey data and the predator manipulation experiment failed to find evidence that ground-running spiders reduced herbivore numbers. We therefore suggest that a positive impact of organic fertilisers on wolf spiders in grass,clover agroecosystems may not necessarily improve biological control when compared with conventional farming. [source]