This study will: 1) explore the generality of the natural sex- reversing ability of Hyperolius viridiflavus in the field. A chromosomal analysis will attempt to determine the frequency of sex-reversed individuals. 2) establish a breeding colony of these frogs. 3) analyze plasma, gonad and larynx samples of the three categories of animals (females, genetic and sex-reversed males) and correlate circulating sec steroid levels to morphological and behavioral changes. 4) compare volumes of hypothalamic brain nuclei of individuals in the three categories and in females treated with testosterone and flutamide, an anti-androgen. 5) test the effectiveness of i.) group composition, ii.) exogenous testosterone and flutamide and iii.) gonadotropin releasing hormone agonist and antagonist in affecting sex-reversal in females housed in different group situations. 6) record vocalizations of genetic and sex- reversed males, analyze the recording to determine if they differ, and if so, initiate call playback experiments in the field to determine if females distinguish between the two. The data obtained in this preliminary venture will provide a springboard to many future studies ranging from the neuroendocrine to the evolutionary in scope. This unique model system is sure to provide new insights into mechanisms controlling sec at both the proximate and ultimate levels.
