Effects of photoperiod and temperature on testes, renal epithelium, and pituitary gonadotropic cells of the threespine stickleback, Gasterosteus aculeatus L.

Abstract

Sticklebacks were submitted to photoregimes of 8 h L:16 h D or16 h L:8 h D at temperatures of 20 or 9 °C in winter. The long photoperiod stimulated renal hypertrophy at both temperatures. At 16 h L:8 h D at 20 °C, breeding colours and breeding behaviour also appeared. The kidney was least stimulated and the 3β-hydroxysteroid dehydrogenase reactions in the Leydig cells were weakest in the 8 h L:16 h D, 20 °C group. A vigourous spermatogenesis occurred only in this group. The extension of dilated granulated endoplasmic reticulum in the gonadotropic cells was stronger after treatment with long than with short photoperiods, and most obvious at 16 h L:8 h D, 20 °C. The results point to a close correlation between the activity of the gonadotropic cells and steroidogenesis. Spermatogenesis, on the other hand, did not appear to demand very active gonadotropic cells.