Application of histology in reproductive biology of fisheries studies

Abstract

Analysis of gonad organization and development revealed that Serranus atricauda is a functional simultaneous hermaphrodite. The ovary is classified as asynchronous. Oocyte growth is divided into five stages: stage I (primary growth stage), stage II (yolk vesicle formation), stage III (vitellogenesis), stage IV (oocyte maturation) and stage V (mature egg). The testis is of the unrestricted or lobular spermatogonial type. Spermatogenic cells include spermatogonia, primary and secondary spermatocytes, spermatids (which form cysts in the seminiferous tubules) and spermatozoa (free in the lu men). The histological structure of the gonad and sperm morphology would seem to indicate that this species is an externally fertilizing teleost. The observation of several spermatozoa on a hydrated oocyte within the ovarian lumen suggests, for the first time in this genus, that ‘internal gametic association’ may occur.