Reproductive Cycle of the Estuarine Bivalve, <i>Musculista arcuatula</i> Yamamoto and Habe

133-138A detailed account of the reproductive cycle of M. arcuatula based on histological studies is presented. From the evidence gathered by direct observation of spawning in the laboratory, study of mantle thickness and histological condition of the gonad the following picture of the reproductive cycle of M. arcuatula emerges: (i) the development and maturity of male and female gonad are almost synchronous; (ii) there is a long period when the gonads are ripe indicating that the breeding season is extended in this species with at least two major peaks, one in November and another in April-May intervened by several months of asynchronous spawning, the intensity of which shows variation; (iii) no asexual condition is noticeable in the reproductive cycle, i.e. throughout the year germ cells are present in the gonad laden mantle of the bivalve