Juvenile Intersexuality in a Cyprinid Fish, the Sumatra

The process of sex differentiation and development of the gonad in the Sumatra barb, Barbus tetrazona tetrazona, reared in laboratory conditions was studied histologically in the present study. Gonads of all juvenile fish were initially provided with ovarian structures, which were characterized by the development of germ cells into meiotic prophase and auxocyte stages and by the formation of ovarian cavity, during the period from 20 to 25 days after hatching. The ovary continued to grow steadily in part of the fish on successive days, whereas in other fish it remained in ill-developed states in which sparsely distributed oocytes, a relatively large number of gonial germ cells and compact stromal tissue with increased somatic cells were notable. In gonads of the latter type, testicular development began with clustering of gonial germ cells to form primordial seminal lobules, which indicated definitely the differentiation of spermatogonia, and subsequent initiation of spermatogenesis in some of them. Concomitant degenerative changes of oocytes accompanied in some cases by marked infiltratio