メダカ精巣における性分化開始部位について

抄録

This report deals with the gradient of sex differentiation and the interaction between the germ cells and the somatic cells of the developing testes in the medaka, Oryzias latipes. Interstitial cell, used as a criterion for the differentiation of somatic elements of testes, was detected for the first time at 9.0mm stage, while germ cell in meiosis, used as a criterion for germinal elements, was at 11.5mm stage. According to YAMAMOTO, there was an antero-posterior gradient in the sex differentiation of the medaka. In the present investigation, however, such a gradient was not recognizable. The present investigation revealed that interstitial cell was always found at the very vicinity of the parts where the germ cell in meiosis was observable and that the differentiation of somatic cells into interstitial cells occurred at the stage earlier than that of spermatogonia into spermatocytes. Accordingly, it seems that interstitial cells induce the transformation from spermatogonia to spermatocytes.