Abstract
Avian gonadal activity is known to be controlled by photoperiods. In male Japa-nese quail, testicular activity is stimulated by long days and inhibited by short days. However, the photoperiodic testicular response of the quail is not completely under-stood. Thus, I investigated it under various photoperiodic conditions.
When birds were reared under continuous light (LL) after hatching, they reached maturation in 6 weeks and maintained large testes as long as they were kept under LL. When birds were transferred from LL to a short photoperiod (8L : 16D), their testes showed considerable involution within 2 weeks. However, when birds received the short day treatment for 5 weeks or longer period prior to the long day treatment, their testes showed resistance to involution in the subsequent short day treatment of both young and old birds. Further, when birds were continuously kept under a short photoperiod, they showed spontaneous growth of their testes 12 weeks after hatching. Adult birds, which experienced sexual maturation under the long photoperiod, also showed spontaneous recrudescence of their testes under a short photoperiod after several weeks in the involuted state. These results clearly indicate that a short photoperiod does not always act to inhibit the testes of the Japanese quail. They also suggest that there is a kind of photorefractoriness against short days.
