The role of UV in crab spider signals: effects on perception by prey and predators

Australian crab spiders Thomisus spectabilis sit on the petals of flowers and ambush prey such as honeybees. White-coloured T. spectabilis reflect in the UV (UV+ spiders) and previous research has shown that their presence, curiously, attracts honeybees to daisies. We applied an UV-absorber (Parsol®) to create UV-absorbing (UV–) spiders that did not reflect any light below 395 nm wavelength. These physical changes of visual signals generated by crab spiders caused honeybees to avoid flowers with UV– spiders on their petals. They also affected the perception of UV– spiders by honeybees and a potential avian predator (blue tits). Compared to UV+ spiders, UV– spiders produced less excitation of the UV-photoreceptors in honeybees and blue tits, which translated into a reduced UV-receptor contrast and a reduced overall colour contrast between UV– spiders and daisy petals. Our results reveal that a clean physical elimination of reflection in the UV range affects perception in predators and prey and ultimately changes the behaviour of prey.7 page(s

Similarities in Evasive Behavior of Wolf Spiders (Araneae: Lycosidae), American Toads (Anura: Bufonidae) and Ground Beetles (Coleopterea: Carabidae)

(excerpt) While collecting newly metalnorphosed American toads, Bufo anlericanus Holbrook, we have observed that they exhibited evasive behavior similar to that of adults of the wolf spiders, Pardosa saxatilis (Hentz), Pirata insularis Emerton, Pirata arerzicola Emerton, Pirata piratica (Oliver), and adults of the ground beetle, Elaplrrus ruscarius Say. When pursued or disturbed, the spiders, beetles and toads ran across the pound rapidly for short distances (ca. 1-50 cm). They then stopped abruptly and remained motionless. If they were further pursued, this escape sequence was repeated in the same or another direction. Toads and spiders occasionally moved to shallow water to avoid capture. Spiders ran across the water surface whereas the toads swam partially submerged. N\u27e observed this resemblance in evasive behavior on numerous occasions at ponds on the south edge of Carbondale, Illinois (spiders and toads), 1 krn west of Grinnell, Iowa (spiders and toads), and 1.5 km west of Bloomington, Illinois (spiders, toads and beetles). (Specimens were collected for identification from the latter site.

Molecular Spiders in One Dimension

Molecular spiders are synthetic bio-molecular systems which have "legs" made of short single-stranded segments of DNA. Spiders move on a surface covered with single-stranded DNA segments complementary to legs. Different mappings are established between various models of spiders and simple exclusion processes. For spiders with simple gait and varying number of legs we compute the diffusion coefficient; when the hopping is biased we also compute their velocity.Comment: 14 pages, 2 figure

Spiders as surrogate species in ecological monitoring, habitat classification and reserve selection : a thesis presented in partial fulfilment of the requirements for the degree of Masters of Science in Ecology at Massey University, Palmerston North, New Zealand

The use of invertebrates in the monitoring of terrestrial ecosystems was investigated using spiders as a focal group. In a review of previous literature, spiders were found to meet the majority of criteria required of suitable ecological indicators, including high diversity and abundance, a widespread distribution, easy sampling and sorting, relatively low random fluctuation in population sizes and community composition, a range of dispersal abilities, measurable response to habitat change and representation of other taxa. The main weaknesses of spiders as ecological indicators were the lack of taxonomic expertise and sparse knowledge of baseline biology. However, these disadvantages could be rectified and it was concluded that spiders are suitable for further investigation as ecological indicators, involving field trials and hypothesis testing. The spider communities in the litter, herb and shrub layer of eight sites representing four habitat types within a forest successional series were sampled in Pouiatoa State Forest in Northern Taranaki. There were no distinct trends in spider richness or abundance across the successional series. However, spider species and family composition both reflected the successional stage from which they were taken. Site classifications using DCA and cluster analysis were similar when using either plant or spider data. Spider communities demonstrated potential for use in habitat classification of terrestrial ecosystems. Spiders and seven other ground-active invertebrate groups were sampled with pitfall traps from fourteen forest remnants within the Rangitikei Ecological Region to test whether spiders were able to act as indicators of plant and invertebrate diversity. Within-site richness (α-diversity) of spiders was strongly correlated with that of all other invertebrates combined, but spiders were not good predictors of between-site richness (²- diversity) of all other invertebrates. Correlation between the α- and β-diversities of plants and invertebrates were low, indicating that maximising plant diversity in reserve selection might not maximise invertebrate diversity. It is recommended that ground-active invertebrates be included in surveys of potential forest reserves. Spiders are a useful surrogate group for invertebrate communities and could be more widely used in the assessment, monitoring and management of terrestrial ecosystems

Special Adaptations of Orb Weavers and Prey

Orb weaving spiders have devised both webs and special devices for capturing prey. The prey have also evolved mechanisms for eluding spiders and for living with them. Some of the mechanisms involved are discussed in this paper

Evolution of sociality in Anelosimus Spiders

Most spiders are solitary and aggressive towards cohorts, but some have been found to live in groups and forage communally, even sharing in brood care. The benefits of group living outweigh the costs of inbreeding for these spiders, but how sociality has developed in arachnids is yet unknown. In this study I test the neoteny hypothesis for the origin of sociality in spiders in the Anelosimusgenus, which contains many of the known social spiders. The neoteny hypothesis predicts that due to retaining juvenile traits and maturing at an earlier morph, social spiders will have smaller body sizes than their solitary relatives. Using a novel phylogenetic tree of Anelosimusspecies and other outgroups, I used correlative ancestral reconstruction of traits along with analyses of variance to see if body size decreased with an increase in social level. The tree contained 8 evolutionary replicas of sociality (9 social species, 8 independent evolutions of sociality), therefore making it the perfect platform to test the neoteny hypothesis. There was no difference in body size between sociality levels, and the neoteny hypothesis was rejected. I did however, find evidence that social spiders have smaller clutch sizes, as well as a female-biased sex ratio. This supports the hypothesis that social species evolved small clutch sizes with more females to combat extreme oscillations in their population size, and tells us more about how their sociality may have come to be

Cooperative effects enhance the transport properties of molecular spider teams

Molecular spiders are synthetic molecular motors based on DNA nanotechnology. While natural molecular motors have evolved towards very high efficiency, it remains a major challenge to develop efficient designs for man-made molecular motors. Inspired by biological motor proteins such as kinesin and myosin, molecular spiders comprise a body and several legs. The legs walk on a lattice that is coated with substrate which can be cleaved catalytically. We propose a molecular spider design in which n spiders form a team. Our theoretical considerations show that coupling several spiders together alters the dynamics of the resulting team significantly. Although spiders operate at a scale where diffusion is dominant, spider teams can be tuned to behave nearly ballistic, which results in fast and predictable motion. Based on the separation of time scales of substrate and product dwell times, we develop a theory which utilizes equivalence classes to coarse-grain the microstate space. In addition, we calculate diffusion coefficients of the spider teams, employing a mapping of an n-spider team to an n-dimensional random walker on a confined lattice. We validate these results with Monte Carlo simulations and predict optimal parameters of the molecular spider team architecture which makes their motion most directed and maximally predictable

SPIDERS: Selection of spectroscopic targets using AGN candidates detected in all-sky X-ray surveys

SPIDERS (SPectroscopic IDentification of eROSITA Sources) is an SDSS-IV survey running in parallel to the eBOSS cosmology project. SPIDERS will obtain optical spectroscopy for large numbers of X-ray-selected AGN and galaxy cluster members detected in wide area eROSITA, XMM-Newton and ROSAT surveys. We describe the methods used to choose spectroscopic targets for two sub-programmes of SPIDERS: X-ray selected AGN candidates detected in the ROSAT All Sky and the XMM-Newton Slew surveys. We have exploited a Bayesian cross-matching algorithm, guided by priors based on mid-IR colour-magnitude information from the WISE survey, to select the most probable optical counterpart to each X-ray detection. We empirically demonstrate the high fidelity of our counterpart selection method using a reference sample of bright well-localised X-ray sources collated from XMM-Newton, Chandra and Swift-XRT serendipitous catalogues, and also by examining blank-sky locations. We describe the down-selection steps which resulted in the final set of SPIDERS-AGN targets put forward for spectroscopy within the eBOSS/TDSS/SPIDERS survey, and present catalogues of these targets. We also present catalogues of ~12000 ROSAT and ~1500 XMM-Newton Slew survey sources which have existing optical spectroscopy from SDSS-DR12, including the results of our visual inspections. On completion of the SPIDERS program, we expect to have collected homogeneous spectroscopic redshift information over a footprint of ~7500 deg$^2$ for >85 percent of the ROSAT and XMM-Newton Slew survey sources having optical counterparts in the magnitude range 17<r<22.5, producing a large and highly complete sample of bright X-ray-selected AGN suitable for statistical studies of AGN evolution and clustering.Comment: MNRAS, accepte

Preliminary Survey of the Terrestrial Isopods (Isopoda), Millipedes (Diplopoda), Harvestmen (Opiliones), and Spiders (Araneae) of Toft Point Natural Area, Door County, Wisconsin

Toft Point Natural Area is a National Natural Landmark owned and managed by the University of Wisconsin – Green Bay and located on the Lake Michigan shore of Wisconsin’s Door Peninsula. With twelve biotic communities on 700 acres, Toft Point contains considerable biological diversity. We conducted a preliminary survey of the arachnids (spiders and harvestmen, excluding mites and pseudoscorpions), millipedes (diplopods), and terrestrial isopods (Isopoda: Oniscoidea). Sampling occurred on three dates in 2001 using leaf litter collection with Berlese extraction and a timed collection by hand that incorporated a variety of techniques. Specimens from a 1992 survey and assorted collecting events were also used to compile a species list. The list includes five isopods, four millipedes, six harvestmen, and 113 spiders, including 16 new state records (two millipedes and 14 spiders) and 90 new Door County records. Litter collection and sampling in wetland habitats were both especially productive