Hormonal control of the gonadal regression and recovery observed in short days in male and female doves.

Sexually mature ring doves (Streptopelia risoria) maintained from hatch on a photoperiod of 14 h light : 10 h darkness (14L : 10D) and kept in isolation were transferred to 8L : 16D. This treatment resulted in a partial regression of the ovaries and testes and a fall in the concentration of plasma LH but not of plasma FSH. After 2--3 months exposure to 8L : 16D, the gonads regrew to their original size: this regrowth was accompanied by a parallel increase in the concentration of plasma LH. The responsiveness of the pituitary gland to LH releasing hormone in both sexes after 5 weeks of exposure to 8L : 16D (when the gonads were partially regressed) was similar to the response observed after 15 weeks exposure to this lighting schedule (when the gonads had regrown). It was concluded that the spontaneous recovery of gonadal size in ring doves exposed to 8L : 16D is controlled by the hypothalamus and does not involve changes in the functional capacity of the pituitary gland or of the gonads.