Steroidal feedback on photoperiodic induction of testicular growth and development in two bird species.

ABSTRACT

Present study was performed to demonstrate the effect of exogenous administration of testosterone propionate on photoperiodic induction of testicular growth and development in brahminy myna (Sturnus pagodarum) and baya weaver (Ploceus philippinus). Two groups of brahminy myna and baya weaver (n=5 each) were exposed to15L9D (group-I) and 9L15D (group-II), and received 30 µg of TP bird-1 for 15 days. Then, the photoperiod was reversed; the one receiving15L was exposed to 9L and vice versa. Observations on body mass and testis volume were taken at the beginning and at 15 days interval. In brahminy myna, a significant change in body mass occurred under 9L15D, transfer to 15L9D, but not under 15L9D group, transfer to 9L15D. Also, testes were stimulated under 15L9D transferred to 9L15D, but not under 9L15D transferred to 15L9D. In baya weaver, body mass increased under 15L9D and 9L15D for first 15 days and was maintained until the end of the experiment. Testes enlarged gradually in both groups (15L9D and 9L15D transfer to vice versa), but it regressed in 15L9D group, transferred to 9L15D after 45 days. Taken together it appears that body mass response indicates the photoperiodic effect and gonadal response indicates the hormonal effect. Finally results conclude that the photoperiod and circulating testosterone levels feedback on to hypothalamus regulates reproductive cycle in these birds.