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...

Geographical distribution and new records of Ariamnes longissimus keyserling, 1891 (Araneae, Theridiidae) in South America

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Geographical distribution and new records of Ariamnes longissimus keyserling, 1891 (Araneae, Theridiidae) in South America

Abstract

Ariamnes longissimus plays a relevant ecological role as a predator, yet its distribution remains underestimated, reflecting knowledge gaps. This study updates its distribution, reports new occurrences, and discusses biogeographic implications. Primary and secondary data (118 records) were compiled, georeferenced, and mapped according to biomes and political divisions. We report the first occurrence in Bahia (Northeast Brazil) and in the Cerrado. The species occurs in Argentina, Peru, and 10 Brazilian states, predominantly in the Atlantic Forest (78%) and Pampas (16%), with additional records in the Amazon and Cerrado. The concentration of records in southern and southeastern Brazil (94%) suggests either sampling bias or historical barriers, whereas its rarity in the Cerrado and absence in the Caatinga/Chaco indicate an association with humid environments. This distribution may be linked to paleoecological corridors between the Amazon and Atlantic Forest during humid periods of the Miocene–Pleistocene. We conclude that the distribution of A. longissimus is broader than previously expected but remains underestimated, with ecological plasticity evidenced by its occurrence across multiple biomes.


SOARES, D. S., MUNIZ, J. I., MARTINS, M. D. C., SILVA, A. D. D., & ALENCAR, C. E. R. D.. (2026). Geographical distribution and new records of Ariamnes longissimus keyserling, 1891 (Araneae, Theridiidae) in South America. Anais Da Academia Brasileira De Ciências, 98(2), e20250891. https://doi.org/10.1590/0001-3765202620250891