Social behaviour of spitting spiders (Araneae: Scytodidae) from Singapore

The social organization of Scytodes sp., a spitting spider from Singapore, was investigated in the field and in the laboratory. The characteristics considered were colony structure, maternal care, prey capture, prey sharing, adults provisioning with prey and how feeding regime influences the level of tolerance expressed by juveniles that were living together. The characteristics of this species were compared with those of other Scytodes species that have been studied previously. Based on our findings, we conclude that in this species, social organization is 'periodic-social', with extended maternal care, this being a type of 'subsociality'. The females of Scytodes sp. wrapped their eggs in a silk egg sac and used their chelicerae to hold the eggs until they hatched. Spiderlings tended to remain in their mother's web until the fourth instar (i.e. after the third moult) but they were also highly aggressive and cannibalistic towards conspecifics after the third instar. Females carried prey to their spiderlings and either fed alongside the brood or left them to feed alone. Spiderlings also captured large prey cooperatively by spitting onto, biting and feeding on it together. The occurrence of cannibalism among her juveniles did not appear to be influenced by whether the adult female was present or not, nor did it appear to be influenced by prey abundance.     

Determination of the maximum and minimum lethal temperatures (LT50) for Loxosceles intermedia Mello-Leitão, 1934 and L. laeta (Nicolet, 1849) (Araneae, Sicariidae)

In this study, the maximum and minimum lethal temperatures (LT₅₀) of L. intermedia and L. laeta were determined in two treatments: gradual heating (25–50°C) and cooling (25°C to −5°C), and 1 h at a constant temperature. In gradual temperatures change, L. intermedia mortality started at 40°C and the LT₅₀ was 42°C; for L. laeta, mortality began at 35°C and the LT₅₀ was 40°C. At low temperatures, mortality was registered only at −5°C for both species. In the constant temperature L. intermedia showed a maximum LT₅₀ at 35°C and L. laeta at 32°C; the minimum LT for both species was −7°C.     

Sound is involved in multimodal communication of Loxosceles intermedia Mello-Leitão, 1934 (Araneae; Sicariidae)

Signals of different modalities are involved during courtship of the brown spider Loxosceles intermedia. A spine on the pedipalp is rubbed against the grooves on the retrolateral region of the chelicerae producing stridulatory signals, which have a dominant frequency of the airborne component range around 770 Hz for females and around 170 Hz for males. These values are significantly lower for the substrate-borne component. The sound pressure level of stridulatory signals lies below 50 dB and the velocity values below 1 mm/s. The copulation frequency does not depend on the presence of pedipalps in females; however, in males the removal of pedipalps decreases the courtship frequency. During courtship, females vibrate their abdomens after being touched by the courting male, producing tremulatory signals with the dominant frequency below 100 Hz, sound pressure level below 60 dB and velocity below 3 mm/s. This vibration may function as a sign of the akinesia state since it precedes the introduction of the embolus. Cuticular compounds probably determine the recognition of the male by the female. Data from the present study corroborate the generalist nature of L. intermedia in which signals of different modalities are used during courtship.     

Identification,cloning and functional characterization of a novel dermonecrotic toxin (phospholipase D) from brown spider (Loxosceles intermedia) venom

Brown spider bites are associated with lesions including dermonecrosis, gravitational spreading and a massive inflammatory response, along with systemic problems that may include hematological disturbances and renal failure. The mechanisms by which the venom exerts its noxious effects are currently under investigation. It is known that the venom contains a major toxin (dermonecrotic toxin, biochemically a phospholipase D) that can experimentally induce dermonecrosis, inflammatory response, animal mortality and platelet aggregation. Herein, we describe cloning, heterologous expression, purification and functionality of a novel isoform of the 33 kDa dermonecrotic toxin. Circular dichroism analysis evidenced correct folding for the toxin. The recombinant toxin was recognized by whole venom serum antibodies and by a specific antibody to a previously described dermonecrotic toxin. The identified toxin was found to display phospholipase activity and dermonecrotic properties. Additionally, the toxin caused a massive inflammatory response in rabbit skin dermis, evoked platelet aggregation, increased vascular permeability, caused edema and death in mice. These characteristics in combination with functional studies for other dermonecrotic toxins illustrate that a family of dermonecrotic toxins exists, and includes a novel member with high activity that may be useful for future structural and functional studies.     

Loxosceles niedeguidonae (Araneae, Sicariidae) a new species of brown spider from Brazilian semi-arid region

A new species of recluse spider, Loxosceles niedeguidonaesp. n., is described from the Parque Nacional Serra da Capivara, State of Piauí, Brazil. This is the first endemic species described from Brazilian semi-arid environment. The species is included in gaucho group of Gertsch (1967) due to its spermathecal shape and is considered close to Loxosceles chapadensis Bertani, Fukushima & Nagahama, 2010 by the unusual long male palpal tibia, a character not common for species of this group. An updated key for Loxosceles species of gaucho group is presented.     

The evolution of sociality in the spitting spider, Scytodes fusca (Araneae: Scytodidae)—evidence from observations of intraspecific interactions

The intraspecific behaviour of the communal-territorial spitting spider, Scytodes fusca , from North Queensland, Australia, is described from laboratory observations. This spider is tolerant of most conspecific intruders on the web but adults, particularly females, do display aggression to other adults by charging, chasing and spitting. During courtship, both the male and the female tap on the web. Courtship in S. fusca is similar to that of a non-social scytodid Scytodes thoracica. Males often stay with the female for a time after mating. Adults appear to be more cannibalistic toward third than toward first and second instar juveniles, This finding is discussed in relation to the mechanisms of intraspecific recognition. The social behaviour of S. fusca is compared with that of other scytodids and the possible evolution of sociality in S. fusca from the parent offspring association is discussed.     

Scavenging by spiders (Araneae) and its relationship to pest management of the brown recluse spider

Experiments reported in Sandidge (2003; Nature 426: 30) indicated that the brown recluse spider, Loxosceles reclusa Gertsch & Mulaik, preferred to scavenge dead prey over live prey and that the spiders were not detrimentally affected when fed insecticide-killed crickets. Extrapolations made in subsequent media coverage disseminating the results of this research made counter-intuitive statements that pesticide treatment in houses would increase brown recluse populations in homes. This information was presented as if the scavenging behavior was specialized in the brown recluse; however, it was more likely that this behavior has not been well studied in other species. To provide a comparison, the current laboratory study examined the likelihood of non-Loxosceles spiders to scavenge dead prey. Of 100 non-Loxosceles spiders that were tested (from 11 families, 24 genera, and at least 29 species from a variety of spider hunting guilds), 99 scavenged dead crickets when offered in petri dishes. Some of the spiders were webspinners in which real-world scavenging of dead prey is virtually impossible, yet they scavenge when given the opportunity. Therefore, scavenging is a flexible opportunistic predatory behavior that is spread across a variety of taxa and is not a unique behavior in brown recluses. These findings are discussed in relation to pest management practices.     

Siamspinops, a new selenopid spider genus from Southeast Asia (Arachnida, Araneae)

Examination of a collection of selenopid spiders from Southeast Asia resulted in recognition of a new genus, Siamspinops gen. nov., which is erected to accommodate four new Southeast Asian species. Siamspinops spinosissimus sp. nov. (the type species; the male and female are described), S. spinosus sp. nov. (female) and S. allospinosus sp. nov. (female) are recorded from Thailand, S. spinescens sp. nov. (female) from the Malay Peninsula.     

Tracking a medically important spider: climate change, ecological niche modeling, and the brown recluse (Loxosceles reclusa)

Most spiders use venom to paralyze their prey and are commonly feared for their potential to cause injury to humans. In North America, one species in particular, Loxosceles reclusa (brown recluse spider, Sicariidae), causes the majority of necrotic wounds induced by the Araneae. However, its distributional limitations are poorly understood and, as a result, medical professionals routinely misdiagnose brown recluse bites outside endemic areas, confusing putative spider bites for other serious conditions. To address the issue of brown recluse distribution, we employ ecological niche modeling to investigate the present and future distributional potential of this species. We delineate range boundaries and demonstrate that under future climate change scenarios, the spider's distribution may expand northward, invading previously unaffected regions of the USA. At present, the spider's range is centered in the USA, from Kansas east to Kentucky and from southern Iowa south to Louisiana. Newly influenced areas may include parts of Nebraska, Minnesota, Wisconsin, Michigan, South Dakota, Ohio, and Pennsylvania. These results illustrate a potential negative consequence of climate change on humans and will aid medical professionals in proper bite identification/treatment, potentially reducing bite misdiagnoses.     

Prey use of the fishing spider Dolomedes triton (Pisauridae,Araneae): an important predator of the neuston community

Summary Prey of feeding juvenile and adult Dolomedes triton (Walckenaer 1837) were sampled over two seasons on three small ponds in central Alberta, Canada. Prey were mainly insects active at the water surface with truly aquatic species making up about 14% of the diet. Throughout the season aquatic and semi-aquatic Heteroptera represented about 30% of the prey. Diptera and adult Odonata were also important prey items but their abundance in the diet was more variable seasonally. Of the 625 prey items recorded nearly 50% were represented by taxa taken no more than once by spiders in one of the five size classes (adult females, adult males, large, intermediate and small juveniles). Large spiders did not take the smallest prey available, although small and intermediate-sized spiders fed on nearly the full size range taken by larger spiders. Cannibalism was common, accounting for 5% of the observations, with females and large juveniles as the most frequently observed cannibals. We hypothesize that intraguild predation (including cannibalism) could be an important coevolutionary force structuring phenology, population dynamics and microhabitat use of the predatory guild of the neuston community.     

High aquatic niche overlap in the newts Triturus cristatus and T. marmoratus (Amphibia,Urodela)

We studied spatial niche metrics of large-bodied newts (Triturus cristatus and T. marmoratus) in three breeding ponds in western France. Adults and larvae were sampled with underwater funnel traps. Larvae were identified to the species with diagnostic microsatellite DNA markers. The distribution of adult T. cristatus and T. marmoratus across pond regions differed in one out of six cases, no differences were observed between larvae (two ponds studied). Niche overlap and niche breadth indices across resource states defined as pond regions or individual traps were high (Schoener's C: pond regions 0.60–0.98, traps 0.35–0.71; Levins' B: pond regions 0.71–0.98, traps 0.35–0.76). Adults of large-bodied newts significantly differed in resource use from small-bodied newts (T. helveticus). The results are discussed in view of the occurrence of interspecific breeding attempts, and the unpredictable ecological characteristics of newt breeding ponds.     

Thermal biology of zebrafish (Danio rerio)

Zebrafish has become one of the most important animal models in research. Most of the variables studied using zebrafish are influenced by water temperature. The objective of this review was to analyze the published data on the thermal biology of the zebrafish. The paper first provides a brief introduction to zebrafish ecology and thermal tolerance, and continues with a review of the influence of temperature on several physiological variables, including development, growth, metabolism, reproduction, behavior, circadian biology and toxicology. Although a number of papers have already studied the effects of temperature on the zebrafish biology, knowledge in this field is still scarce, especially compared with other model organisms such as the rat, and therefore further research should be encouraged.     

Coexistence and competition within Acartia (Copepoda,Calanoida) congeners from Lebanese coastal water: niche overlap measurements

Annual succession and ecological niche formation among six dominant coexisting species of the genus Acartia were studied between 1979 and 1989. The coexisting species: A. discaudata, A. clausi, A. grani, A. italica, A. josephinae and A. latisetosa formed dense populations at different periods in Jounieh harbour (Central Lebanon, eastern Mediterranean). Using numerical data analysis, I defined and measured niche hyperspaces and niche overlaps of these species. Although both spatial and temporal segregation occurred between congeners, the amount of niche overlap was estimated in relation to the availability, use, and abundance of natural resources. The hydrobiological factors prevailing in the port were considered resource states. They include eight parameters: water temperature and salinity, dissolved oxygen, mineral phosphate, nitrate, chlorophyll-a concentration, plankton biomass, and species diversity of the plankton community. Some competition occurred between the co-existing species and an attempt is made to estimate this. As a result of this competition different ecological niches have developed for each species. Niche overlaps, their hyperspaces, and niche breadth between the congeners are estimated and computed using several indices, such as those based on Levin's and Lloyd's formulae. Two groups of Acartia congeners are defined: a group of spring affinity formed by A. clausi, A. discaudata, and A. grani and a second group involving A. italica, A. josephinae and A.-latisetosa, showing a spring-summer tendency. These coexisting species exhibited certain strategies in their opportunistic behaviours, in order to adapt to a highly variable marine environment, such as the one found in Jounieh port.     

Effect of temperature on hatching and nest site selection in the Green lynx spider, Peucetia viridans (Araneae:Oxyopidae)

1.

Thirty-seven Peucetia viridans egg sacs were incubated at 15, 17.5, 20, 25, 30, 32.5 or 35 °C. Hatching time was inversely proportional to temperature, and no hatching occurred at the extremes (15, 17.5 and 35 °C).