Photoperiodic testicular response and photorefractoriness in common Indian rosefinch.

Two groups of male Rosefinches were pretreated with short photoperiods (8L : 16D) for 60 days to eliminate refractoriness. One group was continued under the same treatment for another 120 days, and the other was transferred to photostimulatory long photoperiods (15L : 9 D) for 70 days. A group of birds having testes of minimal size (combined testicular weight=5-8 mg) was also exposed to natural daylength. Periodic laparotomy during exposure to long photoperiods indicated that gonadal growth occurred in birds on long daylengths followed by regression (photorefractoriness) . Short photoperiods, in contrast, did not initiate testicular recrudescence. NDL birds also showed testis growth on experiencing the increasing daylengths of summer. The results demonstrate that the Rosefinch is a photosensitive bird in which short photoperiods are ineffective while long photoperiods induce gonadal recrudescence which is followed by regression, with continued exposure to long daylengths.