New Insight Into the Evolutionary Arms Race Between Spider Egg Sac Pseudoparasitoids and Active Maternal Care by the Spiders

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  New Insight Into the Evolutionary Arms Race Between Spider Egg Sac Pseudoparasitoids and Active Maternal Care by the Spiders ABSTRACT Pseudoparasitoids can lead to high mortality in spider egg sacs, and in some cases, they reduce the reproductive success of a spider female to zero. On the other hand, a species that develops within the spider's egg sac uses a limited resource derived from a single egg sac for its larval development. Therefore, the most crucial behaviour that increases the fitness of free-living pseudoparasitoid females is choosing the best host for their offspring. We analysed various points of the counter-adaptations of the spider egg sac pseudoparasitoid and spiders exhibiting active maternal care, utilising the ichneumonid  Hidryta fusiventris  (Thomson, 1873) and the wolf spider  Pardosa lugubris  (Walckenaer, 1802). We showed that the oviposition decision of  H. fusiventris  is based on the spider's egg sac size and that the fema...

Diversification of spider silk properties in an adaptive radiation of Hawaiian orb-weaving spiders

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Diversification of spider silk properties in an adaptive radiation of Hawaiian orb-weaving spiders

Introduction: The design of biological structures and the materials composing those structures are intimately connected to performance in biological systems. Spider webs present an excellent example of how design and materials interact during their function in capturing prey. Major shifts in how spider webs capture prey have occurred due to evolutionary changes in both web architecture and silk properties. However, these shifts are mostly described for long timescales deep within the spider’s tree of life. Hawaiian Tetragnatha presents an opportunity to ask if such shifts can occur at much shorter timescales because web design diverges significantly among closely related species on the same island while also converging with more distant relatives on other islands. Here, we provide an initial test of whether or not silk properties diversified during the recent adaptive radiation of Hawaiian Tetragnatha.

Methods: We obtained radial and capture spiral silk from orb webs for spiders on two islands and tested their tensile and adhesive properties. We also used solution-state NMR to compare the composition of low molecular weight compounds in the glue because of their influence on capture spiral stickiness.

Results: Results showed differences in the stiffness of radial silk among four populations of Hawaiian Tetragnatha, while extensibility remained unchanged. Although not statistically different, radial strength and toughness varied twofold among species. Stickiness varied threefold among the four populations of orb weavers. No conspicuous qualitative differences in the low molecular weight compound composition of aggregate glue were found, suggesting that differences in capture spiral stickiness were due to the amount or arrangement of glue droplets on threads.

Discussion: While our sampling is modest, our data provide the first evidence that silk properties can evolve measurably over the relatively short timescales of the adaptive radiation of Hawaiian Tetragnatha spiders.


M., A., Jain, D., Dhinojwala, A., & Blackledge, T. A. (2024). Diversification of spider silk properties in an adaptive radiation of Hawaiian orb-weaving spiders. Frontiers in Arachnid Science, 3, 1386353. https://doi.org/10.3389/frchs.2024.1386353