METHYLTESTOSTERONE-INDUCED DIFFERENTIATION OF A SEMINAL VESICLE HOMOLOGUE IN JUVENILE GOLDFISH, CARASSIUS AURATUS L.

In male goldfish, a structure homologous to the seminal vesicles of other fishes develops from the posterior sterile region of testicular ridges coincidentally with the initiation of spermatogenesis in the anterior region. Sexually differentiated juvenile goldfish were administered with methyltestosterone (50 μg/g diet) for a period of 20 days from 40 (experiment I) and 60 days (experiment II) after hatching. In both experiments, androgen administration exerted inhibitory influences on germ cell development in both sexes, but rather promoted the formation of the ovarian lumen, and of its residues in male gonads as well, accompanied with columnar hypertrophy and ciliation of the epithelium. The same treatment brought about a prominent development of the seminal vesicle homologues in the caudalmost gonadal ridges of females as well as in those of males in experiment II but not in experiment I. The cause of difference in the effects between the two experiments seemed to be ascribable to an incomplete prolongation of the gonadal ridges up to the presumptive area of the organ at the start of experiment I. Thus the capacity of the seminal vesicle primordia, common to both sexes, to make their due differentiation in response to exogenous androgen is confirmed in this study.