9306523 Staub The goal of this research planning grant is to describe the endocrinological mechanisms underlying the normal expression of male-like secondary sexual characteristics in females of several species in the salamander genus Aneides. The project tests the hypothesis that the expression of these male-like traits in females of several species of Aneides is a consequence of higher levels of circulating plasma androgens or androgen receptors in target tissues relative to females which lack these traits. To accomplish this, the following studies are planned: 1) documentation of the secondary sexual characteristics of the jaw musculature of males and females, 2) characterization of the androgen receptors in the jaw musculature of males and females, and 3) determination of levels of circulating plasma androgens and estrogens in males and females. Results will be analyzed in a phylogenetic framework with the goal of understanding how endocrinological variation can explain the dramatic morphological variation expressed within the genus Aneides. In some salamander species, females express male-like traits, such as enlarged jaw musculature. The goal of the proposed research is to describe the hormonal basis of the expression of these traits in females of several species in the salamander genus Aneides. The proposed project tests the hypothesis that the expression of these male-like traits in females is a consequence of higher levels of androgens (e.g. testosterone) or androgen receptors in the jaw musculature relative to females which lack these traits. The proposed research 1) compares male and female jaw musculature, 2) examines levels of androgen receptor binding in the jaw musculature of males and females, and 3) surveys levels of circulating sex hormones (androgens and estrogens) in males and females. The primary significance of the proposed project is that it will provide information on the role of androgens in the development of normal female characteristics, a role that has remained relatively unexplored. ***
