A Cuticle, Temperature and Respiration.- I Chelicerate Cuticle Structure.- II Coloration and Chromes.- III Thermal and Water Relations.- IV Behavioural Temperature Regulation.- V Behavioural and Physiological Adaptations to Cold.- VI Respiratory System: Structure and Function.- VII Heart Rate and Physiological Ecology.- VIII Moulting Hormones.- B Glands, Silk and Webs.- I Glandular Aspects of Sexual Biology.- II Communication with Chemicals: Pheromones and Spiders.- III Spider Venoms and Their Effect.- IV Comparative Structure and Histochemistry of Silk-Producing Organs in Arachnids.- V Fine Structure and Function of Capture Threads.- VI Chemistry, Physical Properties, and Synthesis of Araneidae Orb Webs.- VII Ecological Aspects of Spider Webs.- C Feeding Ecology.- I Structure and Function of the Digestive Tract.- II Excretory Organs.- III The Prey of Spiders.- IV Feeding Ecology of Winter-Active Spiders.- V Kleptobiosis in Spiders.- VI Hunger and Starvation.- D Parasites.- I Nematode Parasites of Spiders.- II Spider-Hunting Sphecid Wasps.- III The Biology of Acroceridae (Diptera): True Endoparasitoids of Spiders.- E Environment and Life History.- I Life Cycles and Diapause.- II Dispersal: Ballooning and Other Mechanisms.- III Growth, Foraging and Reproductive Success.- IV The Biorhythms of Spiders.- References.

Ecophysiology of Spiders

Synthetic genes encoding recombinant spider silk proteins have been constructed, cloned, and expressed. Protein sequences were derived from Nephila clavipes dragline silk proteins and reverse-translated to the corresponding DNA sequences. Codon selection was chosen to maximize expression levels in Escherichia coli. DNA "monomer" sequences were multimerized to encode high molecular weight synthetic spider silks using a "head-to-tail" construction strategy. Multimers were cloned into a prokaryotic expression vector and the encoded silk proteins were expressed in E. coli upon induction with IPTG. Four multimer, ranging in size from 14.7 to 41.3 kDa, were chosen for detailed analysis. These proteins were isolated by immobilized metal affinity chromatography and purified using reverse-phase HPLC. The composition and identity of the purified proteins were confirmed by amino acid composition analysis, N-terminal sequencing, laser desorption mass spectroscopy, and Western analysis using antibodies reactive to native spider dragline silk. Circular dichroism measurements indicate that the synthetic spider silks have substantial beta-sheet structure.

Construction, Cloning, and Expression of Synthetic Genes Encoding Spider Dragline Silk

Genetic engineering of fibrous proteins: spider dragline silk and collagen.

THE orb web of the garden spider Araneus diadematus, like those of other ecribellate orb spiders, relies on the remarkable extensibility of its sticky capture spiral to intercept and entrap prey1,2. The spiral strands consist of core fibres and an all-enveloping aqueous coat, which forms into a pattern of droplets3. The core fibres are paired and probably made of typical spider silk4,5. The aqueous solution droplets are more or less evenly spaced6 and are required to allow the special mode of extension of the fibres3,7. Knowledge of the chemical composition and general physical properties of this liquid phase is necessary to understand its function in web mechanics and prey capture8. We have now investigated the chemical composition of this aqueous solution and found the droplets to be a concentrated solution of hygroscopic substances related to neurotransmitters. We offer an explanation as to the function and origin of this solution.

Compounds in the droplets of the orb spider's viscid spiral

A partial cDNA clone, from the 3′ end of the dragline silk gene was isolated from Nephila clavipes major ampullate glands. This clone contains a 1.7-kb insert, consisting of a repetitive coding region of 1.4-kb and a 0.3-kb nonrepetitive coding region; 1.5-kb of the 1.7-kb fragment was cloned into Escherichia coli and a␣43-kDa recombinant silk protein was expressed. Characterization of the purified protein by Western blot, amino acid composition analysis, and matrix-assisted laser desorption ionization/time-of-flight mass spectrometry confirms it to be spider dragline silk.

Purification and Characterization of Recombinant Spider Silk Expressed in Escherichia Coli

The digestive fluid of Argiope was assayed for its proteolytic activity with selected natural and synthetic substrates.



1
Peak proteolytic activity was observed at pH 7.8. This was coincident with the pH of the digestive fluid.

2
Elastolytic and weak chymotryptic activities were detected. Limited activity toward collagen was also observed. Activity toward substrates for trypsin, leucine aminopeptidase and carpboxypeptidase A and B was absent.

3
Evidence demonstrating the in vitro digestion of web fibroin was obtained. The viscid spiral was susceptible to a variety of proteases; the radial fibers to the spider enzyme alone.

4
Of a series of inhibitors studied, EDTA had the greatest effect upon the spider proteases. This effect was temperature dependent.

E. J. Kavanagh

Papers

The alkaline proteases of Argiope and their possible role in web digestion