Snake venom is an ecologically critical functional trait, primarily applied for foraging and accordingly shaped by selective pressures. Recent insights underpinned the high variability of snake venoms down to the intraspecific level, with regional, ontogenetic, and seasonal variation being mostly investigated. In contrast, sex-based venom variation has received considerably less attention so far, and its influence on venom compositions is poorly described. Here, we compare venom profiles and bioactivity from pooled male and female samples of Central European adders (Vipera berus) to provide insights into potential sex-based venom variation in this species. Proteomics, paired with SDS-PAGE and RP-HPLC, revealed highly similar venom profiles. Likewise, phospholipases A2 and proteases activity profiling, as well as bioassays targeting the effects of venom on the coagulation cascade and the viability of different mammalian cell lines revealed similar activity spectra. Our results do not suggest a noteworthy extent of sex-based intraspecific venom variation in V. berus. We further discuss our data in light of the species' venom composition at larger geographic scales and its clinical relevance. This work contributes to a clearer framework for understanding venom biology in the world's most widespread medically relevant venomous snake.

This study investigated the individual variation in the procoagulant toxicity of Vipera aspis venoms collected from multiple Swiss localities, in addition to the neutralisation capacity of three currently available antivenoms. Functional coagulation assays revealed quantifiable geographic differences in venom potency and clotting kinetics. Mechanistic analyses demonstrated that V. aspis venoms exert their procoagulant effects primarily through Factor Va-dependent action of the coagulation cascade, leading to accelerated thrombin generation and clot formation. These findings highlight the complexity of venom-host interactions, showing that Factor Va acts as a multifactorial cofactor that mediates both Factor X and Factor VII activation and varies between individual specimens. From a clinical perspective, this toxicological variability underscores the challenges or relying on a single antivenom for effective treatment across the vast range of a single species. Understanding the molecular basis of these pathophysiological variations through proteomic or transcriptomic profiling will be critical for developing antivenoms with improved neutralising efficacy. Beyond its clinical toxicology relevance, this work provides novel insight into the ecological and evolutionary forces shaping venom diversity in medically important species and identifies procoagulant enzymes from V. aspis venom as promising lead candidates for therapeutic development.