Agonistic behaviour of female Tegenaria atrica in the presence of different aged spiderlings

The agonistic behaviour of adult female T. atrica increases with increasing age of spiderlings until 80 days post-emergence, then decreases. In all cases, cannibalism of spiderlings increases markedly after completion of their pre-dispersal period with a correlation between the switch of behaviour, from tolerance to cannibalism, and a modification of individual’s cuticular compounds. Experiments that compare spiderlings weight and mobility indicate that female agonistic behaviour are always low with spiderlings in pre-dispersal period, and high with spiderlings in post-dispersal period. Female reproductive state and the weight/mobility of spiderlings are not the only factors controlling the adult female’s agonistic behaviour towards spiderlings on her web, as tactochemical information plays an important role in modulating agonistic behaviour after close contact between female spiders and spiderlings. The agonistic behaviour of females appears to correspond with a change in the increase of polar compound levels (methylesters and fatty acids) and the decrease of apolar compound levels (hydrocarbons) in spiderlings of different ages.     

Assignment of the three disulfide Bridges of huwentoxin-I, a neurotoxin from the spiderSelenocosmia huwena

The positions of the disulfide bonds of huwentoxin-I, a neurotoxin from the spiderSelenocosmia huwena, have been determined. The existence of three disulfide bonds in the native toxin was demonstrated by mass spectroscopy and the lack of reactivity with a thiol reagent. The assignment procedure involved a combination of tryptic digestion of the native toxin and sequence analysis of both intact andin situ S-carboxymethylated toxin.In situ carboxymethylation is shown to be a useful procedure in sequencing of cysteine- and cystine-containing peptides. Sequence analysis of the intact, cross-linked toxin indicated that no amino acid phenylthiohydantoin (PTH) derivative is seen for the first half-cystine in a cross-linked pair, but that the PTH of dehydroalanine, which can be detected at 313 nm, is seen at the position of the second half-cystine. By sequencing disulfide cross-linked tryptic fragments, the three disulfide linkages in huwentoxin-I could be assigned as Cys₂-Cys₁₇, Cys₉-Cys₂₂, and Cys₁₆-Cys₂₉.     

A countrywide survey of colour morph frequencies in the spider Enoplognatha ovata (Glerck) (Araneae: Theridiidae): evidence for natural selection

Data on the frequencies of the main colour morphs ( lineata, redimita and ovata ) of Enoplognatha ovata have been collected from a total of 454 Ordnance Survey 10 km squares distributed throughout Great Britain. Only c. 0.5% of samples were monomorphic, for lineata in each case. Multiple regression analysis has been used to assess possible associations between morph frequencies and principal components derived from nine environmental variables. The distribution of morph frequencies is not random but shows weak clines associated with certain climatic factors. These large scale clines indicate the action of natural selection although very local variations in morph frequencies may result from selection and/or drift.     

The consequences of adult foraging success on the components of lifetime fitness in a semelparous,sit and wait predator

Summary We evaluated the role of adult foraging success in the lifetime fitness of female crab spidersMisumena vatia. Misumena are semelparous, sit and wait predators that hunt for insect prey on flowers, in this study primarily on inflorescences (umbels) of milkweedAsclepias syriaca. We used path analysis to integrate previously performed experimental and observational studies, thereby establishing the magnitude, correlations and causal relationships of key foraging and life history variables and their roles in lifetime fitness. A path proceeding from maternal hunting patch choice through maternal mass, clutch mass and number of dispersal-age young was the dominant element and explained a large part of the variation. Other paths that incorporated parasitism of the egg mass and predation of young leaving the nests made only small impacts on variation. No trade-offs were found, primarily because a single factor, maternal mass (a maternal effect) resulting from foraging success, provided major benefits for successive life history stages. Since differences in the numbers of eggs, egg loss and mortality at dispersal resulted almost entirely from differences in maternal mass, they are controlled by the maternal generation and, thus, are appropriately attributed to the lifetime fitnesses of the mothers, rather than to those of their offspring.     

Rotational-echo Double-resonance in Complex Biopolymers: a Study of Nephila Clavipes Dragline Silk

Rotational-Echo Double-Resonance (REDOR) NMR on strategically 13C and 15N labeled samples is used to study the conformation of the LGXQ (X = S, G, or N) motif in the major ampullate gland dragline silk from the spider Nephila clavipes. A method is described for calculating REDOR dephasing curves suitable for background subtractions, using probability distributions of nitrogen atoms surrounding a given carbon site, which are developed from coordinates in the Brookhaven Protein Data Bank. The validity of the method is established by comparison to dephasings observed from natural abundance 13C peaks for G and A. Straightforward fitting of universal REDOR dephasing curves to the background corrected peaks of interest provide results which are not self-consistent, and a more sophisticated analysis is developed which better accounts for 15N labels which have scrambled from the intended positions. While there is likely some heterogeneity in the structures formed by the LGXQ sequences, the data indicate that they all form compact turn-like structures.     

蜘蛛听毛的电镜观察

选用新蛛类的9种蜘蛛作为研究的对象，通过听毛的电镜观察探讨听毛在不同类群的差异。研究结果表明：管网蛛科的北京马蹄蛛的毛窝和听毛显然与中纺类，原蛛类和新蛛类中其他科的种类均不相同。拟壁钱科的居室拟壁钱（有筛器蜘蛛）和北国壁钱（无筛器蛛蛛）的毛窝和听毛的结构相差悬殊，很难看出亲缘上的关系，刺瓣似隙蛛和机敏漏斗蛛的毛窝差别大，无法表明它们之间近缘，园蛛科和肖蛸科种类的听毛窝和听毛数目表明两者之间近缘。