An unusually complex venom system in araneophagous palp-footed spiders (Palpimanidae)

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  An unusually complex venom system in araneophagous palp-footed spiders (Palpimanidae) Venoms are key adaptive traits in many animal lineages, yet their structural and functional diversity in spiders remains poorly investigated. Here, we present an initial characterization of the venom system of palp-footed spiders (Palpimanidae), a family specialized in hunting other spiders. Using micro-computed tomography, we found that the venom glands of the single species examined, Palpimanus gibbulus , exhibit a complex, multi-lobed morphology that is unusual among araneomorph spiders. Proteo-transcriptomic analyses of two Palpimanus venoms ( P. gibbulus and P. cyprius ) revealed highly diverse putative toxin repertoires comprising hundreds of peptides and proteins, including numerous novel putative neurotoxins, cytotoxins, enzymes, and allergens. Five major families of cysteine-rich palpitoxins were identified as the dominant putative neurotoxic components in both species, displaying con...

Comparative microscopic anatomy of Schizomida – 2. The rostrosoma and the pharyngeal suction pump

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Comparative microscopic anatomy of Schizomida – 2. The rostrosoma and the pharyngeal suction pump

Abstract

This paper tests hypotheses of independent parallel evolution of the rostrosoma among euchelicerate taxa by analyzing the microscopic anatomy and histology of the rostrosoma of Uropygi (Schizomida and Thelyphonida) and comparing it with the morphology of the snout region in other euchelicerates. The study employs analysis of multiple histological serial sections, μCT-imaging, and graphical as well as computer-based 3D reconstruction. Results of the study are that Thelyphonida and Schizomida share the same morphology of the rostrosoma. The rostrosoma of both groups contains a unique arrangement of musculature that is functionally interpreted as pre-oral suction pump. This is followed by a pharyngeal suction pump. The muscles of the pharyngeal suction pump attach to the epistome and the epipharyngeal sclerite. Neither Schizomida nor Thelyphonida possess a postcerebral suction pump as reported earlier. The microscopic anatomy of the rostrosoma of both taxa is unique and does not compare with any of the other euchelicerates, thus supporting the idea of independent evolutionary origin of the rostrosoma. Thelyphonida, Amblypygi and Scorpiones share the occurrence of a large epipharyngeal/epistomal sclerite with associated musculature, which is a feature that lines up with the Arachnopulmonata concept. A comparison with all Euchelicerata taxa shows that the snout region is formed by homologous morphological elements but the specific arrangement, additions and reductions shape the formation of the rostrosoma, so that parallel evolution of homologous parts of the arachnid ground pattern can be assumed that has formed those elements into convergent morphologies.


Starck, J. M. (2024). Comparative microscopic anatomy of Schizomida – 2. The rostrosoma and the pharyngeal suction pump. Arthropod Structure & Development, 81, 101372. https://doi.org/10.1016/j.asd.2024.101372