Meeting Abstract

54.3  Jan. 6  The evolution of high-performance tail muscles in snakes MOON, B.R.*; TULLIS, A; University of Louisiana at Lafayette ; University of 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. Specifically, the shaker muscles in the tails of rattlesnakes can sustain contraction frequencies up to 100 Hz for minutes to hours. To study the evolution of these high-performance muscles, we compared the 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 and their relatives. Rattlesnake tail muscles contracted at the highest frequencies and had the highest aerobic capacity, but only moderate anaerobic capacity. In other species that vibrate their tails, contraction frequencies and enzyme activities varied. Among species, there appears to be a clear relationship between muscle contraction frequency and aerobic capacity, but not between contraction frequency and anaerobic capacity. Furthermore, moderate to high aerobic capacities in the tail muscles probably gradually in viperid snakes, well before the evolution of rattlesnakes, rattles, and highly specialized shaker muscles. We are currently testing whether aerobic capacity is associated with the duration of tail vibration bouts or with the different levels of mechanical energy output that occur with different tail morphologies.