DIURNAL SENSITIVITY OF THE TESTES TO EXOGENOUS TESTOSTERONE PROPIONATE IN SEXUALLY REGRESSED WHITETHROATED MUNIA LONCHURA-MALABARICA

The testes in different groups of whitethroated munia (Lonchura malaba rica) were studied following exogenous treatment of testosterone propi onate (1 mg/100 g body wt./day) at 06.00 h or 14.00 h or 22.00 h for 1 5 consecutive days during the quiescent phase of the annual testicular cycle. The testicular conditions in each group of testosterone treate d and appropriate control (administered only with the vehicle of hormo ne at corresponding time-points) group of birds were analyzed by the s tudies of paired testicular weight, seminiferous tubular diameter, spe rmatogenetic index, and cytology of the testicular germ cells. The res ults of the study revealed that exogenous testosterone was stimulatory to the testicular functions irrespective of the time of treatment. Th e gametokinetic response of the testes to exogenous testosterone also did not show any statistical difference among the birds treated at dif ferent hours of the day. The present study demonstrates for the first time that the responses of the testes to exogenous testosterone during the post-breeding phase in an annual testicular cycle of a wild bird does not vary with the time of administration.