OVULATORY SURGE OF GONADOTROPIN IN THE GOLDFISH, CARASSIUS-AURATUS

The periovulatory pattern of circulating gonadotropin is described for the first time in a poikilothermic vertebrate. In sexually mature female goldfish (Carassius auratus) maintained on a 16L:8D photoperiod, ovulation occurs during the latter part of the dark phase, approximately 20 hr after the fish are warmed from 13 to 21°. Serum gonadotropin levels increase gradually during the first half of the light phase, and by the latter part begin to increase rapidly, reaching the peak of the gonadotropin surge by the onset of the dark phase. Gonadotropin levels remain high through the period of ovulation, and decrease markedly by the onset of the following light phase. The findings indicate that the goldfish provides a valuable model for the study of ovulation in teleosts. © 1979.