Meeting Abstract

P1.158  Wednesday, Jan. 4  Evolution of muscle physiology and reproductive behavior in Anolis lizards KHOZEIN, R.T.*; CASTRO, D.J.; MCCARTHER, N.M.; WADE, J.; JOHNSON, M.A.; Trinity University, San Antonio, TX; Trinity University, San Antonio, TX; Trinity University, San Antonio, TX; Michigan State University; Trinity University, San Antonio, TX

Across animal taxa, the morphology and physiology of muscle fibers are generally associated with the frequency and duration of contractions of those muscles, but these traits remain rarely considered in an explicitly phylogenetic context. In this study, we examined muscles involved in copulation and social display to determine evolutionary relationships between muscle contractile speed, endurance, and the behavioral use of these muscles. We used tissues from ten males of each of nine Anolis lizard species (eight Caribbean species and the green anole Anolis carolinensis) to characterize fibers in a copulatory muscle (retractor penis magnus; or RPM) and a muscle involved in dewlap extension (ceratohyoid). We stained these muscle fibers for myosin ATPase, which provides a measure of contraction speed, and succinate dehydrogenase, which provides a measure of aerobic capacity. With these two stains, we distinguished each fiber as fast-glycolytic (FG; used in quick, high intensity movements), fast oxidative glycolytic (FOG) or slow oxidative (SO; used in longer duration movements), or tonic (T; used in slow movements). Consistent with previous work on the green anole, our results show that RPM fibers are strikingly homogenous across species, while fiber type composition of the ceratohyoid is heterogeneous. In a subset of four species, we found that while all the species have the highest proportion of FOG fibers (compared to other fiber types) in the ceratohyoid, SO fibers appear to be more prevalent in species with low rates of dewlap extension. Together, these results suggest that fiber type evolution may be differentially associated with the behavioral use of muscles in this species group.