Decreasing photoperiods and the testicular cycle of a subtropical bird (spotted Munia),Lonchura punctulata

Abstract

The testicular cycle of subtropical Spotted Munia was studied over a period of 11 months in the following schedules: L/D: 0.25/23.75; L/D: 1/23; L/D: 3/21; L/D: 5/19; L/D: 8/16 and near‐complete darkness. All schedules completely abolished annual gonadal regression with the exception of L/D: 8/16 and near‐complete darkness. In the former, gonads regressed but entered the next reproductive cycle 4 months earlier than the normal scheduled time. In the latter also the cycle was completed though it was sharp and short. It was observed that the greater the duration of the dark period the better the gonadal response is. Sensitivity to short photoperiods/long dark periods seems to be characteristic of the low‐latitude birds; what relevance it has to the normal reproductive cycle of munias in nature is not known.