Composite structure of silken threads and a proteinaceous hydrogel which form the diving bell wall of the water spider Agyroneta aquatica

Dietrich Neumann,Armin Kureck

doi:10.1186/2193-1801-2-223

Abstract

The unique ability of Argyroneta aquatica to form a diving bell web was re-examined using a new approach in a structurally simplified environment. The spiders generated sheet-webs from stiff, anchored threads and bundles of fine threads crossing each other, to which a hydrogel was added in several places. Due to the hydrophilic property of the web, small air bubbles could not pass this composite and remained perfectly spherical at the contact point. As revealed using Coomassie Brilliant Blue, the hydrogel and the silken threads are proteinaceous. The spider uses the web as a diving bell by transporting air bubbles to a small area underneath such a sheet-web, and by additional spinning activities. As revealed by light microscopy, the composite of threads and hydrogel is free of any meshes. In contrast, scanning electron microscopy shows only remnants of the hydrogel.

Highlights

The palearctic diving bell spider, Argyroneta aquatica (Clerck 1757) (Araneae: Cybaeidae) is the only spider which lives and hunts submerged among water plants in ponds, ditches and lakes
The spherical form of air bubbles caught under a sheet-web or inside a new bell indicated that the value of the effective contact angle θe at the point of the three phase contact water/air/sheet-web was close to zero, confirming a physical argument according to which the surface of the wall must be hydrophilic (Woermann 2010)
The proteinaceous hydrogel, which is described here for the first time, corresponds in its properties to an ensemble of hydrophilic macromolecules forming a network in water

Summary

Introduction

The palearctic diving bell spider, Argyroneta aquatica (Clerck 1757) (Araneae: Cybaeidae) is the only spider which lives and hunts submerged among water plants in ponds, ditches and lakes. By means of its plastron, the spider transports air from the water surface to a submersed horizontal sheet-web, forming and filling the bell (Braun 1931, Wesenberg-Lund 1939, Crome 1951, Heinzberger 1974, Masumoto et al 1998, Nuridsany and Pérennou 2004). Both sexes can make diving bells, but the sexes meet and copulate in the bell of the more sessile and smaller female; eggs are kept in a separate bell. This diving bell functions as a physical gill

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