Gametogenesis Of Atrina Maura (Bivalve : Pinnidae) Under Artificial Conditions

Gametogenesis in the Chinese pen-shell bivalve, Atrina maura (Sowerby, 1835) was provoked under artificial conditions in a running water system maintained under constant environmental conditions in semi-closed tanks. The specimens were fed with a diet commonly used in experimental hatcheries. Gametogenesis was described using stereological techniques (based on the oocyte diameters), classical and semi-thin histology procedures, and electron microscopy. Four reproductive stages were recognized based on oocyte size and cytological characteristics of the gonad: early gametogenesis (4-15 mum), growing (16-30 mum), mature (31-45 mum), and degenerating (46-65 mum). During gametogenesis, the auxiliary cells surrounded the oocyte basal region in the growing stage, afterward disappearing. A process of auto- and heterosynthesis characterize the mature stage, and nuclear deterioration and cytoplasmic membrane disintegration define the degenerating stage. The ultrastructural study of gonads showed that the cytological evolutionary process is comparable to those described for other bivalves. Additionally, the use of semi-thin histology permitted observation of oogonia mitosis. The conditioning system used in this experiment allowed the pen-shells to attain gonadal maturity in 35 days. The application of this procedure will permit hatcheries to obtain viable oocytes for larvae culture.