Beyond Venom and Constriction: Bite Performance and Trophic Ecology in the Genus Drymarchon

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  Beyond Venom and Constriction: Bite Performance and Trophic Ecology in the Genus Drymarchon Abstract Snakes exhibit extreme cranial kinesis that facilitates ingestion of prey with large cross-sectional area, but this ability is widely predicted to reduce bite performance due to decreased structural rigidity. Consequently, most large-bodied snakes rely on envenomation or constriction to subdue prey prior to ingestion. Species within the genus Drymarchon represent a notable exception: these large, non-venomous, non-constricting snakes routinely consume a wide range of prey, including large and potentially dangerous vertebrates, using only simple seizing and pinioning behaviors. Here, we quantify bite performance in three species of Drymarchon ( D. corais, D. couperi, and D. melanurus ), examine morphological predictors of biting performance, compare biting pressure to constriction pressure in similarly sized snakes, and synthesize dietary records across the genus. Our results sh...

Functional venom activity and antivenom neutralization in rattlesnakes across Baja California and Gulf of California islands

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Functional venom activity and antivenom neutralization in rattlesnakes across Baja California and Gulf of California islands

Abstract

Snake venoms are complex biochemical phenotypes whose composition can diverge dramatically among taxa, yet the functional and biomedical consequences of such variation remain understudied for many lineages. Here, we characterized the functional activities of venom from multiple rattlesnake species distributed across insular and mainland localities in the Baja California Peninsula and Gulf of California. We quantified phospholipase A2 (PLA2), proteolytic, and fibrinogenolytic activities as well as median lethal doses (LD50) for 55 individuals across Crotalus enyo, C. mitchellii, C. pyrrhus sensu lato, and C. ruber. We also evaluated the neutralization efficacy of the commercial polyvalent antivenom Antivipmyn®. Venom functional activities differed significantly among species. Crotalus mitchellii expressed a neurotoxic phenotype characterized by the highest PLA2 activity, the lowest LD50 values, and minimal proteolysis. Crotalus pyrrhus and C. ruber expressed proteolytic phenotypes with high enzymatic activity and ubiquitous dual-chain fibrinogenolysis. Crotalus enyo exhibited intermediate functional activities with moderate enzymatic output and the most efficient antivenom neutralization among species. Although Antivipmyn® neutralized the lethal activity of all venoms, efficacy differed significantly among species in both mass-normalized (mgAV/mgV) and potency-scaled (LD50-equivalents per vial) metrics. Notably, insular and mainland populations within species showed qualitative variation in both functional activities and antivenom responses. These results establish that the focal species possess functionally distinct venom phenotypes with species-specific consequences for antivenom neutralization, underscoring the relevance of venom functional characterization for clinical management of envenomation across the Baja California region.
Hirst, S. R., Neri-Castro, E., Vázquez-García, E., Zarzosa, V., Olvera, F., VanHorn, C. M., Alagón, A., Franz-Chávez, H., Castañeda-Gaytán, G., Parkinson, C. L., Strickland, J. L., Borja, M., & Margres, M. J. (2026). Functional venom activity and antivenom neutralization in rattlesnakes across Baja California and Gulf of California islands. Toxicon, 109266. https://doi.org/10.1016/j.toxicon.2026.109266