Breeding under unpredictable conditions: Annual variation in gonadal maturation, energetic reserves and plasma levels of androgens and corticosterone in anurans from the Brazilian semi-arid

Abstract

Anurans living in arid and semi-arid habitats are subjected to unpredictable rain patterns. Consequently, they should be prepared to reproduce at the onset of rain events. We investigated the covariation between calling behavior, testicular maturation, abdominal fat body index (FBI), plasma levels of androgens (T-DHT) and corticosterone (CORT) of males from three species of anurans in the Brazilian semi-arid during the reproductive period and drought. One of these species aestivates during the drought, while the other two species remain foraging. Although the three species display different behavioral strategies during the dry period, they present the same general reproductive patterns. T-DHT levels on the plasma and germinative cyst diameters were higher during the reproductive and breeding period compared to the drought. Additionally, the germinative cysts had all cell stages including sperm bundles during the dry season, however, it was only during the breeding event that free spermatozoa were found in the cyst lumen. These results suggest that these species present the reproductive pattern typical of desert anurans, consisting of opportunistic breeders that reproduce when triggered by a rain stimulus. Rhinella jimi and Pleurodema diplolister had higher CORT when males were calling. Moreover, Rhinella granulosa and P. diplolister showed lower FBI during breeding event, when males were calling. The high levels of CORT and lower FBI during reproductive period are associated, indicating that CORT modulates the recruitment of energy stores to prepare and maintain reproduction, particularly the expensive calling effort.