LYNCH, K.S.; RYAN, M.J.; WILCZYNSKI, W.; Univ. of Texas, Austin; Univ. of Texas, Austin; Univ. of Texas, Austin: Gonadal Steroids, Time Constraints and Mate Choice Plasticity

Plasticity in mate choice may arise from time constraints imposed as time to release eggs approaches. We have previously reported that female tungara frogs (Physalaemus pustulosus) display flexibility in mate choice as they progress through a single reproductive cycle. Repeated phonotaxis tests showed that females increase receptivity (response to conspecific call) and permissiveness (response to less attractive hybrid call) as time to oviposit approaches. Here, we test the hypotheses that circulating gonadal steroids serve as a mechanism to increase receptive and permissive behaviors. Phonotaxis tests assayed female receptivity, permissiveness and discrimination. We administered one of five doses of human chorionic gonadotropin (HCG) and measured response before and after injection. The results show that female response to a conspecific call significantly increases after injection with 500IU (P=.002) and 1000IU (P<.001). Females in these groups significantly decrease response time to a conspecific signal (P<.001) after injection. We also found that female response to an artificial hybrid call increase only at the highest dose, 1000IU (P=.001). There is also a significant decrease in response time to an artificial hybrid call (P=.05) after injection. Changes in permissiveness, however, were not due to a decrease in discrimination. Furthermore, females that laid eggs after treatment were significantly more likely to respond to a conspecific call (P<.0001) and a hybrid call (P=.02) than females that never laid eggs. Together, these data suggest that receptivity is increases first but if fertilization does not occur then permissive behaviors appear. We also conclude that female behavior may be altered as the time to egg release approaches and gonadal steroids serve to modulate these behavioral changes. Supported by NSF 0078150 and NIMH T32 MH18837.