How to assess musculature and performance in a constricting snake? A case study in the Colombian rainbow boa (Epicrates cenchria maurus)

Abstract

The ability of a living organism to perform specific actions such as prey capture or predator avoidance is a critical feature that should affect individual fitness. Snakes have an elongate morphology that lacks the regional variation associated with girdles found in limbed vertebrates. In this context, this group offers interesting opportunities to study specific forms and functions. In this study, we examined musculature in a medium-sized boid snake, the Colombian rainbow boa Epicrates cenchria maurus, by combining two methods: magnetic resonance imaging (MRI) and calliper measurements after axial palpation. The MRI demonstrated an important development of epaxial musculature consistent with the predatory mode of constriction. We showed that MRI and palpation data were strongly correlated, indicating that musculature is an easily measurable phenotypic feature in the studied species. The calliper method was then applied in combination with assessments of physical performance (constriction and defence capabilities) in a group of snakes after a prolonged fast and again after a re-feeding period. A clear relationship was detected between dorsal musculature and both maximal traction and constriction forces. Re-feeding significantly increased dorsal musculature and traction capabilities. While musculature assessments are classically difficult to achieve among tetrapods, this study suggests that snakes are interesting models for examining variation in musculature and performance in natural and experimental conditions.