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

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.