Meeting Abstract

20.7  Jan. 5  Estradiol induces female receptivity to conspecific calls in the t�ngara frog CHAKRABORTY, M**; BURMEISTER, S. S; University of North Carolina, Chapel Hill; University of North Carolina, Chapel Hill mukta@email.unc.edu

Sex steroid hormones play crucial roles in mediating reproductive behaviors. In most vertebrates sex hormones such as estradiol and progesterone induce female receptivity. Female túngara frogs use acoustic cues for making mate-choice decisions and have high estradiol (E) and progesterone (P) concentrations when they are sexually receptive. To experimentally assess the effect of steroid hormones on receptivity to conspecific calls, females with naturally low steroid levels were hormone manipulated and their receptivity measured by phonotaxis choice tests. We found that E-injected females were more likely to be receptive compared to saline-injected females (p < 0.001). HCG (human chorionic gonadotropin) injections alone induced receptivity but females treated with a combination of hCG and fadrozole (an estrogen synthesis inhibitor) were less likely to be receptive than E-injected females (p= 0.002), suggesting that estradiol is necessary for phonotaxis. There was no significant difference in receptivity between E-injected females and E+P-injected females (p= 0.27), or between E-injected females and those injected with hCG alone (p= 0.07). Among receptive females, mean latency to respond to conspecific calls also did not differ among these three treatment groups (p= 0.71). Our results suggest that estradiol is necessary and sufficient to induce receptivity towards conspecific calls in this species and that progesterone does not contribute significantly to receptivity. These data offers exciting avenues for further research on the effects of estradiol in mediating receptivity via the sensory and motor pathways underlying phonotaxis.