A Study on Sexual Maturation of Hen Clam Mactra chinensis Philippi

Gonadal development, the annual reproductive cycle and the first sexual maturity of hen clam, Mactra chinensis were studied histologically. Sexuality of the species was dioecious. The gonads were irregularly arranged from the subregion of mid-intestinal 91an4 in visceral cavity to the reticular connective tissue of the foot. The ripe eggs were about in diameter, and they were surrounded by gelatinous membrane. The spawning period was from May to September when the water temperature ranged , with the peak in June and July. The annual reproductive cycle of Mactra chinensis could be classified into five successive stages; multiplicative, growing, mature, spent, and degenerative and resting. The monthly changes of the fatness coefficient closely correlated with the annual reproductive cycle. Percentages of the first sexual maturity of female and male clams were over among those individuals ranging from 3.5 to 3.9cm, and in those over 5.0cm in shell length.