Semi-aquatic spider silks: transcripts, proteins, and silk fibres of the fishing spider, Dolomedes triton (Pisauridae)

To survive in terrestrial and aquatic environments, spiders often rely heavily on their silk. The vast majority of silks that have been studied are from orb-web or cob-web weaving species, leaving the silks of water-associated spiders largely undescribed. We characterize transcripts, proteins, and silk fibres from the semi-aquatic spider Dolomedes triton. From silk gland RNAseq libraries, we report 18 silk transcripts representing four categories of known silk protein types: aciniform, ampullate, pyriform, and tubuliform. Proteomic and structural analyses (scanning electron microscopy, energy dispersive X-ray spectrometry, contact angle) of the D. triton submersible egg sac reveal similarities to silks from aquatic caddisfly larvae. We identified two layers in D. triton egg sacs, notably a highly hydrophobic outer layer with a different elemental composition compared to egg sacs of terrestrial spiders. These features may provide D. triton egg sacs with their water repellent properties.