Meeting Abstract
39.5 Friday, Jan. 4 Functional morphology and physiology of tail vibration in snakes MOON, B. *; TULLIS, A. ; Univ. Louisiana at Lafayette; Univ. Puget Sound BradMoon@louisiana.edu
Rattling by rattlesnakes is one of the fastest vertebrate movements and involves some of the highest contraction frequencies sustained by vertebrate muscle. In this project, we studied the evolution of these high-performance muscles by comparing the tail vibration frequencies and activities of the enzymes citrate synthase (an indicator of aerobic capacity) and lactate dehydrogenase (an indicator of anaerobic capacity) in the tail muscles of rattlesnakes (Crotalus atrox and others), their nearest relatives (Agkistrodon contortrix, and A. piscivorus), and more distant relatives (Elaphe obsoleta, Lampropeltis getula, Coluber constrictor and others). We found wide variation in tail vibration frequencies, and a clear relationship between muscle aerobic capacity and vibration frequency. We also observed wide variation in tail morphology and the kinematics of tail vibration. In this stage of the project, we are quantifying the morphology and kinematics of tail vibration and testing for relationships among muscle physiology, tail morphology, kinematics, and mechanics. Specifically, we are testing whether the aerobic capacity of tail muscles and duration of tail vibration bouts are associated with the moment of inertia and mechanical work of tail vibration. In most of the study species, only the distal-most 10 or so vertebrae of the tail are involved in short bursts of tail vibration, which indicates that pitvipers and many colubrids vibrate homologous parts of the tail. However, the masses (and hence moments of inertia) and displacements involved in tail vibration differ among species. For example, some species with very long tails (Coluber constrictor and Masticophis sp.) vibrate much or all of the tail for moderate durations, which indicates that tail vibration has evolved differently, or perhaps independently, in diverse lineages. We will quantify this variation and its relationship to muscle aerobic capacity.
