Testicular structure and semicystic spermatogenesis in a specialized ovuliparous species: Scorpaena notata (Pisces, Scorpaenidae)

Study of the histology and ultrastructure of the testes of Scorpaena notata reveals some unusual features in the most basic form of oviparity, termed ovuliparity. Distribution of spermatogonia and subsequent stages of development are consistent with an intermediate type of testes, somewhere between the restricted and unrestricted types. Spermatogenesis is semicystic, a feature rarely found in fish, which may account for the high vacuole count found both in the various spermatogenic phases and in the Sertoli cells. Sertoli cells cover the interior of the testicular lobes and have an initial phase of secretion. They go on to penetrate the lobular lumen and become phagosomes. The spermatozoon has a relatively long midpiece and is surrounded by large quantities of seminal fluid. The sperm makes its way from the central sperm duct to a series of peripheral ducts, where the sperm line up with their heads toward the epithelium and their tails toward the lumen. All indications are that this orientation facilitates the release of sperm onto the gelatinous mass of eggs, and that this could be linked to this type of semicystic spermatogenesis. Results obtained confirm that S. notata is a specialized ovuliparous species.