THE ROLE OF TESTOSTERONE ON MALE MATING BEHAVIOR IN THE AFRICAN CLAWED FROG (XENOPUS LAEVIS)
Karen Zhang, Tyrone Hayes, Alejandra Cabrera, Flor Gowans, Maggie Tsang, Cara He.
University of California, Berkeley, Berkeley, CA.
Atrazine, the second most widely used herbicide in the United States, lowers testosterone levels in male African clawed frogs (Xenopus laevis). Reduced testosterone levels are associated with decreased mating behavior in males. Injecting castrated males with testosterone induced them to mate, suggesting that testosterone is both necessary and sufficient for mating behavior. In the current study, we administered human choriogonadotrion (hCG), which induces endogenous testosterone production, to intact males to determine if testosterone levels affect mating success in males. We predicted that high testosterone levels will result in an increase in mating success. We injected different doses of hCG. Four experimental males were then placed in a pool with 4 control males to compete for 4 females. Males found copulating the next morning were considered successful. After mating sessions, blood samples were taken from the males for testosterone analysis by radioimmunoassay. Results showed more competitive mating in frogs injected with a 50 IU dose of hCG than injected with water, but had similar mating behavior when injecting a 200 IU dose of hCG compared to the full dose. These data suggest that hCG generates a testosterone surge that increases competitive mating behavior, but that all doses used so far may be above a threshold dose associated with mating success.