Venom phenotype conservation suggests integrated specialization in a lizard-eating snake

Biological specialization reduces the size of niche space while increasing efficiency in the use of available resources. Specialization often leads to phenotypic changes via natural selection aligning with niche space constraints. Commonly observed changes are in size, shape, behavior, and traits associated with feeding. One often selected trait for dietary specialization is venom, which, in snakes, often shows variation dependent on diet across and within species. The Neotropical Blunt-headed Treesnake (Imantodes cenchoa) is a highly specialized, rear-fanged, arboreal, lizard hunter that displays a long thin body, enlarged eyes, and a large Duvernoy's gland. However, toxin characterization of I. cenchoa has never been completed. Here, we use RNA-seq and mass spectrometry to assemble, annotate, and analyze the venom gland transcriptomes of four I. cenchoa from across their range. We find a lack of significant venom variation at the sequence and expression levels, suggesting venom conservation across the species. We propose this conservation provides evidence of a specialized venom repertoire, adapted to maximize efficiency of capturing and processing lizards. Importantly, this study provides the most complete venom gland transcriptomes of I. cenchoa and evidence of venom specialization in a rearfanged snake, giving insight into selective pressures of venom across all snake species.

Automated summary

Biological specialization reduces niche space size and increases resource efficiency. Venom is a commonly selected trait for dietary specialization in snakes. This study analyzes the venom gland transcriptomes of the Neotropical Blunt-headed Treesnake (Imantodes cenchoa) and finds evidence of specialized venom adapted for efficient lizard capture and processing. The study provides important insights into venom specialization in rear-fanged snakes and selective pressures of venom across all snake species.