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

Abstract

Our understanding of the extraordinary mechanical and physico-chemical properties of spider silk is largely confined to the fibers produced by orb-weaving spiders, despite the diversity of foraging webs that occur across numerous spider families. Crab spiders (Thomisidae) are described as ambush predators that do not build webs, but nevertheless use silk for draglines, egg cases and assembling leaf-nests. A little-known exception is the Australian thomisid Saccodomus formivorus, which constructs a basket-like silk web of extraordinary dimensional stability and structural integrity that facilitates the capture of its ant prey. We examined the physical and chemical properties of this unusual web and revealed that the web threads comprise microfibers that are embedded within a biopolymeric matrix containing additionally longitudinally-oriented submicron fibers. We showed that the micro- and submicron fibers differ in their chemical composition and that the web threads show a remarkable lateral resilience compared with that of the major ampullate silk of a well-investigated orb weaver. Our novel analyses of these unusual web and silk characteristics highlight how investigations of non-model species can broaden our understanding of silks and the evolution of foraging webs.

Stretchable, Bio-Compatible, Antioxidant and Self-Powering Adhesives from Soluble Silk Fibroin and Vegetal Polyphenols Exfoliated Graphite

“…The ratio of the peak area with respect to the total area was used to estimate the percentage content of secondary structures that are summarized in Figure 2 b. According to previous results [ 9 , 32 ], neat RS consists of random coil and α-helices structures while, for the G-RS/T1 and G-RS/T10 samples, part of the random coils is transformed in β-sheets structures ( Figure 2 b). It is noteworthy that tannins interact with proteins, producing stable complexes; therefore, the presence of only random coils in the RS/T samples can be ascribed to the presence of polyphenols that negatively affect the β-sheet and/or α-helices arrangement.…”

From Bioinspired to Bioinformed: Benefits of Greater Engagement From Biologists

“…While differences in dragline silk mechanical properties are also reported among similarly-sized, closely related species (Kerr et al, 2018), the properties of other types of spider silk have been largely ignored. For example, the potential diversity of the tubuliform and aciniform silk used to construct egg cases is poorly understood, but the remarkably rigid, free-standing foraging web of the thomisid spider Saccodomus formivorus also appears to comprise these silks, which could inspire rigid thread designs for tissue engineering (Haynl et al, 2020). This approach of embracing biodiversity can also be expanded to organisms that live in unusual or hostile habitats.…”