Costs increase as ritualized fighting progresses within and between phases in the sierra dome spider, Neriene litigiosa

Magnitudes and patterns of energy expenditure in animal contests are seldom measured, but can be critical for predicting contest dynamics and understanding the evolution of ritualized fighting behaviour. In the sierra dome spider, males compete for sexual access to females and their webs. They show three distinct phases of fighting behaviour, escalating from ritualized noncontact display (phase 1) to cooperative wrestling (phase 2), and finally to unritualized, potentially fatal fighting (phase 3). Using CO2 respirometry, we estimated energetic costs of male-male combat in terms of mean and maximum metabolic rates and the rate of increase in energy expenditure. We also investigated the energetic consequences of age and body mass, and compared fighting metabolism to metabolism during courtship. All three phases involved mean energy expenditures well above resting metabolic rate (3.5 X, 7.4 X and 11.5 X). Both mean and maximum energy expenditure became substantially greater as fights escalated through successive phases. The rates of increase in energy use during phases 2 and 3 were much higher than in phase 1. In addition, age and body mass affected contest energetics. These results are consistent with a basic prediction of evolutionarily stable strategy contest models, that sequences of agonistic behaviours should be organized into phases of escalating energetic costs. Finally, higher energetic costs of escalated fighting compared to courtship provide a rationale for first-male sperm precedence in this spider species. (C) 2004 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.

The functions of societies and the evolution of group living: Spider societies as a test case

Many models have been advanced to suggest how different expressions of sociality have evolved and are maintained. However these models ignore the function of groups for the particular species in question. Here we present a new perspective on sociality where the function of the group takes a central role. We argue that sociality may have primarily a reproductive, protective, or foraging function, depending on whether it enhances the reproductive, protective or foraging aspect of the animal's life (sociality may serve a mixture of these functions). Different functions can potentially cause the development of the same social behaviour. By identifying which function influences a particular social behaviour we can determine how that social behaviour will change with changing conditions, and which models are most pertinent. To test our approach we examined spider sociality, which has often been seen as the poor cousin to insect sociality. By using our approach we found that the group characteristics of eusocial insects is largely governed by the reproductive function of their groups, while the group characteristics of social spiders is largely governed by the foraging function of the group. This means that models relevant to insects may not be relevant to spiders. It also explains why eusocial insects have developed a strict caste system while spider societies are more egalitarian. We also used our approach to explain the differences between different types of spider groups. For example, differences in the characteristics of colonial and kleptoparasitic groups can be explained by differences in foraging methods, while differences between colonial and cooperative spiders can be explained by the role of the reproductive function in the formation of cooperative spider groups. Although the interactions within cooperative spider colonies are largely those of a foraging society, demographic traits and colony dynamics are strongly influenced by the reproductive function. We argue that functional explanations help to understand the social structure of spider groups and therefore the evolutionary potential for speciation in social spiders.

Discovery of an MIT-like atracotoxin family: Spider venom peptides that share sequence homology but not pharmacological properties with AVIT family proteins

This project identified a novel family of six 66-68 residue peptides from the venom of two Australian funnel-web spiders, Hadronyche sp. 20 and H. infensa: Orchid Beach (Hexathelidae: Atracinae), that appear to undergo N- and/or C-terminal post-translational modifications and conform to an ancestral protein fold. These peptides all show significant amino acid sequence homology to atracotoxin-Hvf17 (ACTX-Hvf17), a non-toxic peptide isolated from the venom of H. versuta, and a variety of AVIT family proteins including mamba intestinal toxin 1 (MIT1) and its mammalian and piscine orthologs prokineticin 1 (PK1) and prokineticin 2 PK2). These AVIT family proteins target prokineticin receptors involved in the sensitization of nociceptors and gastrointestinal smooth muscle activation. Given their sequence homology to MITI, we have named these spider venom peptides the MIT-like atracotoxin (ACTX) family. Using isolated rat stomach fundus or guinea-pia ileum organ bath preparations we have shown that the prototypical ACTX-Hvf17, at concentrations up to 1 mu M, did not stimulate smooth muscle contractility, nor did it inhibit contractions induced by human PK1 (hPK1). The peptide also lacked activity on other isolated smooth muscle preparations including rat aorta. Furthermore, a FLIPR Ca2+ flux assay using HEK293 cells expressing prokineticin receptors showed that ACTX-Hvf17 fails to activate or block hPK1 or hPK2 receptors. Therefore, while the MIT-like ACTX family appears to adopt the ancestral disulfide-directed beta-hairpin protein fold of MIT1, a motif believed to be shared by other AVIT family peptides, variations in the amino acid sequence and surface charge result in a loss of activity on prokineticin receptors. (c) 2005 Elsevier Inc. All rights reserved.

Modulation of insect Cav channels by peptidic spider toxins

Insects have a much smaller repertoire of voltage-gated calcium (Ca-v) channels than vertebrates. Drosophila melanogaster harbors only a single ortholog of each of the vertebrate Ca(v)1, Ca(v)2, and Ca(v)3 subtypes, although its basal inventory is expanded by alternative splicing and editing of Ca-v channel transcripts. Nevertheless, there appears to be little functional plasticity within this limited panel of insect Ca-v channels, since severe loss-of-function mutations in genes encoding the pore-forming a, subunits in Drosophila are embryonic lethal. Since the primary role of spider venom is to paralyze or kill insect prey, it is not surprising that most, if not all, spider venoms contain peptides that potently modify the activity of these functionally critical insect Ca-v channels. Unfortunately, it has proven difficult to determine the precise ion channel subtypes recognized by these peptide toxins since insect Ca-v channels have significantly different pharmacology to their vertebrate counterparts, and cloned insect Ca-v channels are not available for electrophysiological studies. However, biochemical and genetic studies indicate that some of these spider toxins might ultimately become the defining pharmacology for certain subtypes of insect Ca-v channels. This review focuses on peptidic spider toxins that specifically target insect Ca-v channels. In addition to providing novel molecular tools for ion channel characterization, some of these toxins are being used as leads to develop new methods for controlling insect pests. (c) 2006 Elsevier Ltd. All rights reserved.

Impact of ocean acidification and warming on the larval development of the spider crab Hyas araneus from different latitudes (54° vs 79°N), 2010

The combined impacts of future scenarios of ocean acidification and global warming on the larvae of a cold-eurythermal spider crab, Hyas araneus L., were investigated in one of its southernmost populations (living around Helgoland, southern North Sea, 54°N) and one of the northernmost populations (Svalbard, North Atlantic, 79°N). Larvae were exposed at temperatures of 3, 9 and 15°C to present day normocapnia (380 ppm CO2) and to CO2 conditions expected for the near or medium-term future (710 ppm by 2100 and 3000 ppm CO2 by 2300 and beyond). Larval development time and biochemical composition were studied in the larval stages Zoea I, II, and Megalopa. Permanent differences in instar duration between both populations were detected in all stages, likely as a result of evolutionary temperature adaptation. With the exception of Zoea II at 3°C and under all CO2 conditions, development in all instars from Svalbard was delayed compared to those from Helgoland, under all conditions. Most prominently, development was much longer and fewer specimens morphosed to the first crab instar in the Megalopa from Svalbard than from Helgoland. Enhanced CO2 levels (710 and particularly 3000 ppm), caused extended duration of larval development and reduced larval growth (measured as dry mass) and fitness (decreasing C/N ratio, a proxy of the lipid content). Such effects were strongest in the zoeal stages in Svalbard larvae, and during the Megalopa instar in Helgoland larvae.

Seawater carbonate chemistry and biological processes during experiments with spider crab Hyas araneus, 2009

Future scenarios for the oceans project combined developments of CO2 accumulation and global warming and their impact on marine ecosystems. The synergistic impact of both factors was addressed by studying the effect of elevated CO2 concentrations on thermal tolerance of the cold-eurythermal spider crab Hyas araneus from the population around Helgoland. Here ambient temperatures characterize the southernmost distribution limit of this species. Animals were exposed to present day normocapnia (380 ppm CO2), CO2 levels expected towards 2100 (710 ppm) and beyond (3000 ppm). Heart rate and haemolymph PO2 (PeO2) were measured during progressive short term cooling from 10 to 0°C and during warming from 10 to 25°C. An increase of PeO2 occurred during cooling, the highest values being reached at 0°C under all three CO2 levels. Heart rate increased during warming until a critical temperature (Tc) was reached. The putative Tc under normocapnia was presumably >25°C, from where it fell to 23.5°C under 710 ppm and then 21.1°C under 3000 ppm. At the same time, thermal sensitivity, as seen in the Q10 values of heart rate, rose with increasing CO2concentration in the warmth. Our results suggest a narrowing of the thermal window of Hyas araneus under moderate increases in CO2 levels by exacerbation of the heat or cold induced oxygen and capacity limitation of thermal tolerance.

Erection induced by Tx2-6 toxin of Phoneutria nigriventer spider: expression profile of genes in the nitric oxide pathway of penile tissue of mice

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Artificial Skin - Culturing of Different Skin Cell Lines for Generating an Artificial Skin Substitute on Cross-Weaved Spider Silk Fibres

Background: In the field of Plastic Reconstructive Surgery the development of new innovative matrices for skin repair is in urgent need. The ideal biomaterial should promote attachment, proliferation and growth of cells. Additionally, it should degrade in an appropriate time period without releasing harmful substances, but not exert a pathological immune response. Spider dragline silk from Nephila spp meets these demands to a large extent. Methodology/Principal Findings: Native spider dragline silk, harvested directly out of Nephila spp spiders, was woven on steel frames. Constructs were sterilized and seeded with fibroblasts. After two weeks of cultivating single fibroblasts, keratinocytes were added to generate a bilayered skin model, consisting of dermis and epidermis equivalents. For the next three weeks, constructs in co-culture were lifted on an originally designed setup for air/liquid interface cultivation. After the culturing period, constructs were embedded in paraffin with an especially developed program for spidersilk to avoid supercontraction. Paraffin cross-sections were stained in Haematoxylin & Eosin (H&E) for microscopic analyses. Conclusion/Significance: Native spider dragline silk woven on steel frames provides a suitable matrix for 3 dimensional skin cell culturing. Both fibroblasts and keratinocytes cell lines adhere to the spider silk fibres and proliferate. Guided by the spider silk fibres, they sprout into the meshes and reach confluence in at most one week. A well-balanced, bilayered cocultivation in two continuously separated strata can be achieved by serum reduction, changing the medium conditions and the cultivation period at the air/liquid interphase. Therefore spider silk appears to be a promising biomaterial for the enhancement of skin regeneration.

Interactions between Spider Silk and Cells - NIH/3T3 Fibroblasts Seeded on Miniature Weaving Frames

Background: Several materials have been used for tissue engineering purposes, since the ideal matrix depends on the desired tissue. Silk biomaterials have come to focus due to their great mechanical properties. As untreated silkworm silk has been found to be quite immunogenic, an alternative could be spider silk. Not only does it own unique mechanical properties, its biocompatibility has been shown already in vivo. In our study, we used native spider dragline silk which is known as the strongest fibre in nature. Methodology/Principal Findings: Steel frames were originally designed and manufactured and woven with spider silk, harvesting dragline silk directly out of the animal. After sterilization, scaffolds were seeded with fibroblasts to analyse cell proliferation and adhesion. Analysis of cell morphology and actin filament alignment clearly revealed adherence. Proliferation was measured by cell count as well as determination of relative fluorescence each after 1, 2, 3, and 5 days. Cell counts for native spider silk were also compared with those for trypsin-digested spider silk. Spider silk specimens displayed less proliferation than collagen-and fibronectin-coated cover slips, enzymatic treatment reduced adhesion and proliferation rates tendentially though not significantly. Nevertheless, proliferation could be proven with high significance (p<0.01). Conclusion/Significance: Native spider silk does not require any modification to its application as a biomaterial that can rival any artificial material in terms of cell growth promoting properties. We could show adhesion mechanics on intracellular level. Additionally, proliferation kinetics were higher than in enzymatically digested controls, indicating that spider silk does not require modification. Recent findings concerning reduction of cell proliferation after exposure could not be met. As biotechnological production of the hierarchical composition of native spider silk fibres is still a challenge, our study has a pioneer role in researching cellular mechanics on native spider silk fibres.

Infestation rates of the pedunculated barnacle Octolasmis lowei (Cirripedia: Poecilasmatidae) on the spider crab Libinia spinosa (Decapoda: Majoidea)

The prevalence and infestation intensities of Octolasmis lowei in the bronchial chambers of Libinia spinosa were evaluated according to the host's sex, size, and moult condition. Epibionts were classified as cyprid larvae, non-ovigerous or ovigerous according to their developmental stage. A median intensity of infestation of 21 epibionts/host was found (range = 1-644; Q(3) = 81). Epibiont prevalence values (88%) were higher on ovigerous female hosts than on males (55%) or on non-ovigerous females (31%). Intensity of infestation was positively correlated with host size in both sexes for non-ovigerous and ovigerous epibionts. No preference between host sex by cyprid larvae was observed, nor any correlation between cyprid abundance and host size. Cyprid larvae abundance was positively correlated with settled epibionts on both host sexes. The duration of the intermoult phase was the main factor linked to the establishment of sessile epibionts. These observations are important in relation to crabs that have a terminal moult, because these animals cannot eliminate their epibionts in future moults, thus increasing the importance of density-dependent mechanisms on epibiont establishment; in that way, prevalence of infestation alone can underestimate the real impact of infestation on the host's life cycle.

Taxonomy, phylogeography and myrmecophily of the spider genus Mastigusa (Araneae, Cybaeidae)

The genus Mastigusa Menge, 1854 includes small entelegyne spiders represented by extant and fossil species presenting characteristic features in male and female genitalia. The genus has a palearctic distribution, being present in Europe, North Africa, and the Near East, and shows ecological plasticity, with free-living, cave- dwelling and myrmecophile populations. The taxonomic history of the genus has been problematic, both regarding its phylogenetic placement and the delimitation of the species it includes. Three extant species are currently recognized, but the characters used to discriminate them have been inconsistent, leading to confusion about their identification and distribution. In the present thesis we addressed the taxonomic issues regarding Mastigusa by combining molecular and morphological data in an integrative taxonomy approach. For the first time, we included the genus in a molecular phylogenetic matrix solving a long going debate regarding its familiar placement, obtaining a well-supported placement in the family Cybaeidae. We used multi-locus molecular phylogenetic and DNA barcoding techniques as a starting point for identifying divergent lineages within the genus and revise the taxonomic status of the three known Mastigusa species, identifying a new species from the Iberian Peninsula, Algeria and the United Kingdom: M. raimondi sp. n. This taxonomic revision allowed a phylogeographic and ecological study of Mastigusa across its distribution range, carried out using phylogenetics and ecological niche modelling techniques, aiming at a comparison of the lifestyles and ecological requirements of the different species on a geographic scale. The Italian Alps were finally used as a testing ground for investigating the ecology and host preference of myrmecophile Mastigusa arietina populations living in association with ant species belonging to the Formica rufa species group. Spiders were found in association with five different Formica species, demonstrating little specificity and the tendency of associating with the locally present host species.