Meeting Abstract

P3.27  Monday, Jan. 6 15:30  Endocrine mechanisms of evolutionary changes in body size of Anolis lizards MUELLER, E.*; JENNINGS, D.H.; Southern Illinois University – Edwardsville; Southern Illinois University – Edwardsville dajenni@siue.edu

Vertebrate body size is largely regulated by the actions of pituitary growth hormone (GH) and insulin-like growth factors (IGFs) and adult body size is positively correlated with circulating levels of both GH and IGF. A heterologous ELISA was used to determine circulating GH levels in three species of Anoles that vary in body size (A. sagrei, A. carolinensis, and A. equestris). Plasma dilutions used to validate the assay paralleled the standard curve. Plasma GH levels were lowest A. sagrei, the smallest species. GH levels were higher in A. carolinenesis and A. equestris, but did not differ between the two species despite differences in body size. Within each species, plasma GH levels were correlated with snout-vent length in A. equestris, but not in A. sagrei or A. carolinensis. While, our results suggest that changes in circulating GH levels underlie some differences in body size among Anoles, other components of the growth hormone axis (GH receptors, IGF levels, and IGF-binding proteins) are likely mediators of evolutionary changes in body size in these lizards.