From Scorpion Venom to Infection Research: The Promise of Opis16a (Blog Entry)

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  Opistophthalmus carinatus , a southern African scorpion whose venom contains opistoporin 1, the parent peptide from which researchers derived the shorter antimicrobial peptide Opis16a. Credit: Dan Lee / CC0 1.0 From Scorpion Venom to Infection Research: The Promise of Opis16a A synthetic peptide inspired by a southern African scorpion’s venom shows activity against drug-resistant bacteria—but its potential as a wound treatment remains under investigation. Scorpion venom is a complex mixture of biologically active molecules. While many are studied for their effects on ion channels and the nervous system, others offer a different research opportunity: understanding how peptides can damage bacterial cells. One such candidate is Opis16a , a synthetic, 16-amino-acid fragment derived from opistoporin 1, a peptide originally isolated from the venom of Opistophthalmus carinatus . Research highlighted by Nature Africa suggests that this shortened molecule combines broad antibacterial acti...

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