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Just add water and age! Cribellate silk stickiness increases at high humidity across ontogeny in the Tasmanian cave spider, Hickmania troglodytes

Dakota Piorkowski (1), Niall Doran (2), Chen-Pan Liao (1), Chung-Lin Wu (3), Sean Blamires (4) & I-Min Tso (1)

(1) Department of Life Science, Tunghai University, Taichung, Taiwan, ROC
(2) Bookend Trust, Hobart, Tasmania, Australia
(3) Centre for Measurement Standards, Industrial Technology Research Institute, Hsinchu, Taiwan, ROC (4) Evolution & Ecology Research Centre, The University of New South Wales, Sydney, Australia


Cribellate silk is a composite of puffy cribellar nano-fibrils that surround strong axial fiber generates van der Waals and hygroscopic forces that adhere and entangle captured prey in webs. Maintaining attachment of prey to the web is of high importance to the spider, as it needs to locate and subdue struggling prey within seconds. Therefore, understanding how biotic and abiotic factors, such as ontogeny and humidity, influence the adhesive performance of these threads can provide insights into the preferred foraging habitats and capture abilities, particularly for spiders living in harsh environments. We tested the adhesive performance of cribellate silk from the Tasmanian cave spider, H. troglodytes (Family: Austrochilidae); an ancient spider with a long lifespan that lives in caves of near complete atmospheric water saturation. We found that silks tested at high humidity (>90% RH) generated more force at detachment and performed more work of adhesion than silks tested at lower humidity (~45% RH). Interestingly, we also found adhesive properties to increase with ontogeny, which we speculate is due to increased number of cribellar fibrils as shown in other species, but only when tested at high humidity. Our results demonstrate a unique case where the extreme conditions of the cave environment enhance the performance of a phenotypic feature in a spider. Furthermore, our findings highlight the importance of the incorporation and use of water in a capture silk system typically seen as a “dry” adhesive.

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Dakota Piorkowski, Niall Doran, Chen-Pan Liao, Chung-Lin Wu, Sean Blamires & I-Min Tso