11-Ketotestosterone at a dose of 200 μg/g diet was administered to fry of Tilapia mossambica daily for 19 days from 7 to 25 days after hatching, and the effects on gonadal sex differentiation were examined histologically.
The treatment caused a masculinization of the gonad in most treated fish. Cysts of young oocytes together with gonial germ cells occurred in affected gonads of presumed genetic females at the end of treatment. However, these oocytes were retarded in development and degenerated thereafter. These gonads could develop into testes which had many spermatogenetic germ cells and efferent ducts. On the other hand, gonads of possible genetic males continued to develop into structurally defined testes as those of control fish under the influence of 11-ketotestosterone.
It is concluded from these results that 11-ketotestosterone is effective in directing gonadal sex differentiation toward males in Tilapia mossambica, and that the period from 7 to 25 days after hatching, during which morphological sex differentiation of the gonad occurs and proceed, includes the critical stage for inducing gonadal masculinization by exogenous androgen.
- Nippon Suisan Gakkaishi is an official journal of the Japanese Society of Fisheries Science written in Japanese only.
The society publishes an English journal, Fisheries Science, as well, which accepts submissions from non-members of the society over the world. Detailed information is available in http://jsfs.jp/en/journals/fisheries-science.