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

Abstract

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.

Spidroins and Silk Fibers of Aquatic Spiders

“…A previous study of spidroins from one semi-aquatic spider, D. triton , did not detect modifications associated with wet environments 37 . However, now with spidroin sequences from additional species, we observed a dramatically higher concentration of hydrophobic amino acid motifs in Sp sequences in the water-associated A. aquatica , D. marina , and D. triton (20–38% GV) compared to the terrestrial B. longinqua and S. mimosarum (2–4% GV).…”

“…Thus, we named each of them with only “Sp” for “Spidroin” and no indicator of type, such as the “Am,” “Cr,” “Py,” or “Tu” of AmSp, CrSp, PySp, and TuSp following the nomenclature of previous works with undetermined spidroin types (e.g. 1,37,59,61 ). Maximum likelihood analyses shows one of the Sp sequences ( B. lon _Sp_N_vB) groups with a S. mimosarum spidroin ( S. mim _Sp2b) and their clade is positioned outside a diverse clade that includes pyriform, flagelliform, and cribellar spidroins (Fig.…”

“…Alternatively, if environment is a major selective force shaping spidroin sequences, spidroins from the water-associated spiders A. aquatica and D. marina could share more similarities. Furthermore, A. aquatica and D. marina spidroins may share similarities with those of another semi-aquatic spider, Dolomedes triton 37 (Pisauridae).…”

1000 spider silkomes: Linking sequences to silk physical properties

“…Pioneering work by Gatesy et al (14) identified and analyzed spidroin sequences from several spider lineages, including basal spider groups, thus enabling a glimpse into the complex evolution of spidroin sequences. Subsequently, there have been a large number of studies that have explored the subject of spidroin sequence diversity and evolution, including focused studies on various spidroin paralogs (15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29), and those from more phylogenetic perspective (7,(30)(31)(32)(33)(34), predominantly based on the conserved terminal sequences. On the other hand, the mechanical properties of silk fibers are governed largely through the repetitive regions that dominate the silk protein sequence, and the study on the diversity of spidroin repetitive regions, particularly in the more evolutionarily divergent taxa, has been limited to date.…”

Free-standing spider silk webs of the thomisid Saccodomus formivorus are made of composites comprising micro- and submicron fibers

“…The water repellent effect of the basket web may be partly due to the mesh-like surface of the web, which led to reduced physical interactions with water droplets, similar to the rough surface of non-wetting lotus plant leaves 40 . High hydrophobicity has also been observed in the silk used to form egg cases in other spider species 41 , 42 . The basket web further showed no overall stickiness, indicating the absence of aggregate-like silks, which provide the flagelliform silk of orb webs with adhesiveness for prey capturing 5 , 43 .…”