Seasonal variations of serum constituents in the oyster Crassostrea gigas in Hiroshima Bay.

Oysters Crassostrea gigas cultured in Hiroshima Bay were examined for several serum constituents as well as biochemical composition of soft tissues. The level of carbohydrate in soft tissues reached a maximum (28-38% on dry basis) in May, decreasing steadily to a minimum (2-3%) in September. Serum levels of glucose, carbohydrate, protein, non-protein nitrogen, phospholipid and triglyceride ranged 0.2-1.5, 7-46, 39-98, 1.7-5.5, 0.9-3.7 and 0.1-2.2mg/dl, respectively. They showed essentially the same seasonal variations, having a maximum in May or June, de-creasing steadily until September or October. Close relationships were demonstrated between levels of serum constituents and the annual reproductive cycle, suggesting that the transport of serum constituents is activated in the maturing period of gonads.