Venomics of the six-eyed sand spider, Sicarius rugosus (Araneae: Sicariidae), from the neotropical dry forest of Costa Rica

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  Venomics of the six-eyed sand spider, Sicarius rugosus (Araneae: Sicariidae), from the neotropical dry forest of Costa Rica Abstract Background Sicarius rugosus , the only member of the genus that inhabits Central America, is phylogenetically related to South American  Sicarius  spiders. These originated from a common ancestor with sister African species. Like  Loxosceles ,  Sicarius  exhibits venom phospholipase D activity due to a group of toxins known collectively as SicTox. Methods A gel-assisted, bottom-up, proteomic analysis was performed to characterize the venom composition of  S. rugosus . Hyaluronidase activity was determined using zymography. Results We identified several SicTox sequences, all classified as β-clade paralogs and sharing unique peptides with proteins from  S. patagonicus ,  S. peruensis,  and other species. Enzymes such as metalloproteinases, including putative astacins, carboxypeptidases, and angiotensin-conv...

Extreme sexual size dimorphism correlates with proxies of postcopulatory sexual selection across selected Dolomedes fishing spiders

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Extreme sexual size dimorphism correlates with proxies of postcopulatory sexual selection across selected Dolomedes fishing spiders

Abstract

Sexual size dimorphism (SSD) and mating system diversity are key factors shaping reproductive evolution, yet their relationships with post-mating sexual selection remain incompletely understood. Here, we use a comparative framework across multiple species of Dolomedes fishing spiders to examine how mating systems, sperm production strategies, and proxies of postcopulatory selection relate to SSD. We quantified testes size and spermatogenesis in three closely related species— D. tenebrosus, D. okefinokensis, and D. scriptus —that differ in mating system and SSD. Dolomedes tenebrosus, a monogynous species with extreme female-biased SSD (eSSD) and male self-sacrifice, showed evidence of termination of spermatogenesis at maturity, indicating a terminal investment strategy. Dolomedes okefinokensis exhibited a similar pattern, suggesting convergent evolution toward monogyny. In contrast, D. scriptus, with moderate SSD and a polygynous system, maintained continuous spermatogenesis, consistent with repeated mating opportunities. Expanding to 13 Dolomedes species, we found a strong positive association between eSSD, monogyny, and spermatogenesis termination, alongside increased spermophor volume in eSSD species. These findings suggest that eSSD is associated with both a terminal male reproductive strategy and intensified investment in sperm transfer structures. Together, our results highlight an integrated evolutionary link between sexual size dimorphism, mating system, and male reproductive investment across Dolomedes spiders.

Linde, M., Donke, E., Schwartz, S. K., Hebets, E., & Michalik, P. Extreme sexual size dimorphism correlates with proxies of postcopulatory sexual selection across selected Dolomedes fishing spiders. Evolution. https://doi.org/10.1093/evolut/qpag041