Meeting Abstract
Androgens facilitate the expression of male reproductive traits in many animal species, and muscles are among the primary androgenic targets. In particular, androgens bind to androgen receptors (AR) to induce physiological changes in muscle size, strength, and energetic capacity – changes that can directly influence the behaviors in which those muscles are used. In this study, we examined AR localization in 27 species of Anolis lizards to test the hypothesis that the evolution of AR expression in a muscle is associated with the behavioral use of that muscle. We conducted field behavioral observations of each species to assess the frequency of copulation and dewlap (throat fan) display, and used immunocytochemistry to quantify AR distribution in the nuclei of the retractor penis magnus (RPM; a muscle that moves the hemipenes in copulation) and the ceratohyoid (CH; the muscle that moves the dewlap). Our preliminary analyses suggest that larger species express less AR in the RPM. Further, while species’ copulation rate is not associated with AR localization in the RPM, circulating testosterone levels were positively correlated with copulation. This suggests that AR in the RPM may play less of a role in mediating copulation behavior than its primary ligand. However, previous work has shown that dewlap display rates are not associated with circulating testosterone. Our current work examines the evolution of AR in the CH to determine whether AR localization is correlated with use of the muscle, which occurs up to several times per minute. Together, these analyses represent the largest comparative study of hormone receptors to date.
