The first genus with four sac-like structures in the vulva in the cobweb spider subfamily Theridiinae Sundevall, 1833 (Araneae: Theridiidae)

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  The first genus with four sac-like structures in the vulva in the cobweb spider subfamily Theridiinae Sundevall, 1833 (Araneae: Theridiidae) Abstract The morphological characters of copulatory organs are the most important basis in spiders for identification. In theridiids, a vulva with four sac-like structures is mostly associated with the subfamily Hadrotarsinae but has never been recorded in Theridiinae. Based on specimens collected from subtropical forest canopies in China, a new Theridiinae genus that has four sac-like structures in the vulva is described: Sactheridion gen. nov., with the type species S. chuan gen. & sp. nov. from Sichuan Province, China. Photos, diagnosis, description, and a distribution map of the new genus and new species are provided. Hu, C., Yao, Z., Liu, J. & Xu, X. (2026) The first genus with four sac-like structures in the vulva in the cobweb spider subfamily Theridiinae Sundevall, 1833 (Araneae: Theridiidae). Zootaxa, 5884 (1), 167–175. http...

Exaptation of an evolutionary constraint enables behavioural control over the composition of secreted venom in a giant centipede

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Exaptation of an evolutionary constraint enables behavioural control over the composition of secreted venom in a giant centipede

Abstract

Venoms are biochemical arsenals that have emerged in numerous animal lineages, where they have co-evolved with morphological and behavioural traits for venom production and delivery. In centipedes, venom evolution is thought to be constrained by the morphological complexity of their venom glands due to physiological limitations on the number of toxins produced by their secretory cells. Here we show that the uneven toxin expression that results from these limitations have enabled Scolopendra morsitans to regulate the composition of their secreted venom despite the lack of gross morphologically complex venom glands. We show that this control is probably achieved by a combination of this heterogenous toxin distribution with a dual mechanism of venom secretion that involves neuromuscular innervation as well as stimulation via neurotransmitters. Our results suggest that behavioural control over venom composition may be an overlooked aspect of venom biology and provide an example of how exaptation can facilitate evolutionary innovation and novelty.

Schendel, V., Hamilton, B.R., Robinson, S.D. et al. Exaptation of an evolutionary constraint enables behavioural control over the composition of secreted venom in a giant centipede. Nat Ecol Evol (2024). https://doi.org/10.1038/s41559-024-02556-9