Advancing the systematics of Araneae: ultraconserved elements phylogenomics demonstrates the non-monophyly of Miturgidae Simon, 1886 and supports the Familial Rank of Systariidae Deeleman-Reinhold, 2001

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  Advancing the systematics of Araneae: ultraconserved elements phylogenomics demonstrates the non-monophyly of Miturgidae Simon, 1886 and supports the Familial Rank of Systariidae Deeleman-Reinhold, 2001 Abstract The systematic status of the family Miturgidae Simon, 1886 and related subfamilies has long been problematic, primarily due to challenges in interpreting morphological characters and limited molecular sampling. In this study, we reconstruct the phylogeny of Miturgidae using ultraconserved elements and estimate its divergence time. Our results suggest that Systariinae does not belong to Miturgidae, but rather is sister to all other families of the Dionycha B clade. Consequently, we elevate it to family rank as Systariidae Deeleman-Reinhold, 2001 and discuss its morphological synapomorphies. Furthermore, our analyses place Miturgidae as the sister clade to Viridasiidae + Selenopidae under multiple phylogenetic methods. Divergence time estimates indicate an ancient origin of...

Changes in the material properties of spider glue droplet proteins accompanied shifts in prey capture biomechanics as cobweb spiders diverged from their orb weaving ancestors

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Changes in the material properties of spider glue droplet proteins accompanied shifts in prey capture biomechanics as cobweb spiders diverged from their orb weaving ancestors

Abstract

Although descended from orb weavers, spiders in the family Theridiidae spin cobwebs whose sticky prey capture gumfoot lines extend from a silk tangle to a surface below. When a crawling insect contacts glue droplets at the bottom of a gumfoot line, the line's weak pyriform anchor releases, causing the taut line to contract, pulling the insect from the surface and making its struggles to escape ineffective. To determine if this change in prey capture biomechanics was accompanied by a change in the material properties of theridiid glue, we characterized the elastic modulus and toughness of the glue droplet proteins of four theridiid species at 20% - 90% relative humidity and compared their properties with those of 13 orb weaving species in the families Tetragnathidae and Araneidae. Compared to orb weavers, theridiid glue proteins had low extensions per protein volume and low elastic modulus and toughness values. These differences are likely explained by the loss of tension on a gumfoot line when its anchor fails, which may prioritize glue droplet adhesion rather than extension. Similarities in theridiid glue droplet properties did not reflect these species’ evolutionary relationships. Instead, they appear associated with differences in web architecture. Two species that had stiffer gumfoot support lines and longer and more closely spaced gumfoot lines also had stiffer glue proteins. These lines may store more energy, and, when their anchors release, require stiffer glue to resist the more forceful upward thrust of a prey.

Opell, B. D., Kelly, S. D., Morris, S. A., & Correa-Garhwal, S. M. (2024). Changes in the material properties of spider glue droplet proteins accompanied shifts in prey capture biomechanics as cobweb spiders diverged from their orb weaving ancestors. Acta Biomaterialia. https://doi.org/10.1016/j.actbio.2024.05.043