Testosterone accelerates the onset of photorefractoriness in baya weaver Ploceus philippinus.

Abstract

The baya weaver Ploceus philippinus, despite its purely tropical origin and tropical/subtropical distribution, exhibits all features of a typically photoperiodic species. The onset of reproduction in this species is triggered by increasing daylength and breeding is terminated by the development of distinct photorefractory phase. In order to ascertain the involvement of androgens in the development of photorefractoriness the long day response of birds was tested after a prior exposure to varied doses of testosterone. Testosterone treatment accelerated the onset of photorefractoriness as judged from the gonadal status, LH-dependent yellow plumage and testosterone-dependent beak pigmentation. While gonadal development and yellow plumage occurred in the control birds due to the stimulatory long photoperiod, the testosterone administered birds failed to show such developments. These findings indicate that testosterone might impair the higher photoresponding mechanisms resulting in the development of photorefractoriness.