Meeting Abstract
Muscles used in short, rapid movements experience a different set of physiological challenges than muscles used for slow movements that require endurance, and muscle physiological traits may evolve to support such specialized movements. In this study, we measured the fiber size and type composition of forelimb muscles in a diverse group of lizard species to determine whether these traits were associated with the frequency and type of locomotor and social behaviors (i.e., push-up displays). Using data from field behavioral observations, we classified three species (green anole, Anolis carolinensis; spiny lizard, Sceloporus olivaceus; and curly tail, Leiocephalus carinatus) as “short burst” species, as they are primarily sit-and-wait predators that run and jump to capture prey, and they perform frequent push-up displays during social interactions. We classified three other species (skink, Scincella lateralis; whiptail, Aspidoscelis gularis; and gecko, Hemidactylus turcicus) as “endurance” species, as they are active foragers that perform frequent, slow crawls, and they do not regularly use push-up displays. Using enzyme stains for myosin ATPase and succinate dehydrogenase in sectioned forelimb muscle tissues, we found that short burst species had a higher proportion of tonic muscle fibers (those most involved in maintaining posture and balance) and larger forelimb muscle fibers than the endurance species. While there was a positive correlation between fiber size and the frequency of rapid locomotor movements among species, there was no relationship between push-up displays and muscle fiber size. These results suggest that the behavioral use of forelimb muscles has influenced the evolution of their physiological traits.
