Meeting Abstract
Animal movements and the muscles that produce those movements are tightly interrelated, as behavioral movements require muscular contractions, and in turn, the use of a muscle can influence the structural and biochemical traits of the muscle. For example, continuously active muscles generally have a higher percentage of fatigue-resistant fibers than muscles used periodically, and muscles used more frequently are often composed of larger fibers. Yet, these traits are rarely examined across species. Here, we test the hypothesis that the types of fibers that compose a muscle (fast or slow twitch; oxidative or glycolytic) and their size evolve in association with the frequency or duration of the contractions of that muscle, using three closely-related pairs of Anolis lizard species. The lizards in each pair share a suite of morphological and ecological specializations to a particular microhabitat, but differ dramatically in the frequency and duration for which the dewlap (a throat fan used in aggressive and courtship displays) is extended. We collected behavioral field data on dewlap use for each species, and then collected the ceratohyoid (CH), the muscle responsible for dewlap extensions, from each species to determine the composition and size of CH fibers. We found a negative correlation between dewlap frequency and duration, such that species either display the dewlap quickly and often, or rarely but for longer durations. We found that species that extend the dewlap rarely and slowly have a higher proportion of slow oxidative fibers, the type associated with endurance, in the CH. We are now determining whether CH fiber size interacts with their type to produce dewlap extension, to understand how behavior and the physiological traits that underlie it have coevolved.
