The gilthead sea bream (Sparus aurata L.) is a marine fish of great importance for fisheries and aquaculture. Fishes of both open sea and captivity farm have a peculiar sex-determination system, being a protandrous hermaphrodite (inverted i.e. from male to female). Here we report the variations between open sea fishes and captivity farm from different points, including pattern of sex inversion, gonadosomatic indices and oogenesis by assessment either histological structure and micropyle formation during the spawning phase by scanning and transmition electron microscopy. Despite the limited number of anchoring points, there were significant relationships of open sea fishes comparing with those of fish farm. The Sparus aurata of fish farm exhibited decreased gonadosomatic indices, retarded oogenesis associated with an increased average of follicular atresia and deformed micropyle formation parallel with fragility and degeneration of egg membrane. All of these manifestations gathered may be causes of failure of spawning in captivity farm. Finally the authors concluded that failure of spawning in captivity farm may result from incomplete sex inversion, failure of sex development of both male and female and defect of micropyle formation.
Key words: Sparus aurata, open sea, Fish farm, Comparative Anatomy
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