INVIVO AND INVITRO EVIDENCE FOR THE ROLE OF HORMONES IN FISH SPERMATOGENESIS

In an attempt to discern general, mechanisms by which specific hormones control certain aspects of fish spermatogenesis, we focus on a single fish species (Fundulus heteroclitus), and, by analogy, generalize to other fishes. At least three androgenic steroids (testosterone, 11-ketotestosterone, 11-beta-hydroxytestosterone) are present in the serum of Fundulus heteroclitus, but only testosterone appears to be associated with spermatogenesis in vitro as well as in vivo. 11-Ketotestosterone appears to be associated with spermiation in vivo, but has not yet been tested for its ability to cause spermiation in vitro. The preponderant androgen present in the serum, 11-beta-hydroxytestosterone, does not appear to be directly associated with spermatogenic process either in vitro or in vivo. In F. heteroclitus, in vivo studies indicate that at least two different gonadotropins are produced, on that primarily causes steroid production and a second that causes testicular growth. Indirect evidence suggests that production of these gonadotropins is seasonal in terms of both their amounts and their relative proportions.