1994 Volume 42 Issue 4 Pages 619-625
The process of gonadal sex differentiation in tiger puffer, Takifugu rubripeswas studied histologically. Paired primordial gonads were found under the mesonephric ducts of a fish 7 days after hatching. The gonads were sexually indifferent until 40 days. The first sign of ovarian differentiation was the formation of ovarian cavity, which was observed in the gonads of about a half of fishes at 45-50 days. The increase of oogonium in number became evident from 55-65 days, and the oocytes appeared at 86 days. The gonads which lacked the ovarian cavity were still sexually indifferent at 55-65 days. The germ cells began to increase at 55-65 days in the peripheral region of the gonads without ovarian cavity. This characteristic showed the testicular differentiation. The beginning of meiosis in the testis was not observed until 105 days. The sperm duct began to form in posterior region of the testis at 75 days. The features of intersexuality were not found in this study.
