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 conserved sequence motifs but distinct species-specific expression profiles. Our discovery of an unusual venom gland architecture in P. gibbulus and the diverse venom repertoires of the two araneophagic Palpimanus species broadens our understanding of the morphological and molecular diversity of spider venom systems.