Ovarian follicular kinetics in response to enucleation and parietal shielding in Rana cyanophlyctis

Abstract

Ovarian follicular kinetics, gravimetric changes in the ovary and the oviduct, were studied in the skipper frog, Rana cyanophlyctis, following enucleation (ENX) and parietal shielding (PS), during the breeding reason. PS was to prevent extraoptic photoreception by the pineal via the frontal organ. The gonadosomatic index (GSI) was high in ENX and PS frogs (P < 0.01). The highest GSI occurred in frogs that were both ENX and PS (P < 0.01). Percentage of oviductal weight decreased (P < 0.01) in PS frogs and increased (P < 0.01) in those subjected to both ENX and PS. Oviductal weight of ENX frogs was unchanged. Data on follicular kinetics revealed a decrease (P < 0.01) in the ENX group in the number of first growth phase (FGP) oocytes and atretic follicles (AF), whereas the number of medium-sized secondary growth phase (MSGP) oocytes and large-sized secondary growth phase (LSGP) oocytes increased (P < 0.01). There was a similar pattern of follicular kinetics in ENX+PS frogs. However, following PS, the number of FGP oocytes and AF increased (P < 0.01) and decreased (P < 0.01) in the MSGP and LSGP oocytes. The lower oviductal weight in PS frogs correlated with reduced SGP oocytes, the major source of estrogen. The importance of lateral eyes and the frontal organs in the transduction of environmental signals to the neuroendocrine- reproductive axis is indicated in this species. That recruitment of FGP to SGP is inhibited only in the PS group suggests that the frontal organ plays an important role in ovarian follicular kinetics.