Zoological Institute and Museum, University of Greifswald, Loitzer Straße 26, D-17489 Greifswald, Germany.
Department of Life Sciences, Tunghai University, Taichung, Taiwan.
Sci Rep. 2019 Jun 24;9(1):9092. doi: 10.1038/s41598-019-45552-x.
Web-building spiders are an extremely diverse predatory group due to their use of physiologically differentiated silk types in webs. Major shifts in silk functional properties are classically attributed to innovations in silk genes and protein expression. Here, we disentangle the effects of spinning behavior on silk performance of the earliest types of capture threads in spider webs for the first time. Progradungula otwayensis produces two variations of cribellate silk in webs: ladder lines are stereotypically combed with the calamistrum while supporting rail lines contain silk that is naturally uncombed, spun without the intervention of the legs. Combed cribellate silk is highly extensible and adhesive suggesting that the reserve warp and cribellate fibrils brings them into tension only near or after the underlying axial fibers are broken. In contrast, these three fiber components are largely aligned in the uncombed threads and deform as a single composite unit that is 5-10x stronger, but significantly less adhesive, allowing them to act as structural elements in the web. Our study reveals that cribellate silk can occupy a surprisingly diverse performance space, accessible through simple changes in spider behavior, which may have facilitated the impressive diversification of web architectures utilizing this ancient silk.
织网蜘蛛是一个非常多样化的捕食群体，因为它们在网中使用生理上分化的丝类型。丝功能特性的主要转变经典归因于丝基因和蛋白表达的创新。在这里，我们首次解开了蜘蛛织网中最早类型的捕获线的纺丝行为对丝性能的影响。Progradungula otwayensis 在网中产生两种变化的栉状丝：梯线刻板地用栉梳梳理，而支撑轨线包含自然未梳理的丝，没有腿的干预而纺制。梳理栉状丝具有很高的延展性和粘性，表明储备经丝和栉状纤维仅在底层轴纤维断裂附近或之后才被拉紧。相比之下，这些三根纤维成分在未梳理的线中基本对齐，并作为一个单一的复合单元变形，该单元强度高 5-10 倍，但粘性显著降低，使其能够作为网中的结构元件发挥作用。我们的研究表明，栉状丝可以占据一个惊人多样化的性能空间，通过蜘蛛行为的简单改变即可获得，这可能促进了利用这种古老丝的令人印象深刻的蛛网结构多样化。
