GAMETOGENIC AND SPAWNING PATTERNS OF MANILA CLAMS TAPES-PHILIPPINARUM(BIVALVIA, VENEROIDA) IN 2 LAGOONS OF THE RIVER PO DELTA, ITALY

The reproductive cycle of the manila clam (Japanese littleneck clam), Tapes philippinarum (Adams and Reeve), was studied in the Po River Del ta of Italy. Different stages of the reproductive cycle were described : active, ripe, spawning, resorption and inactive. Specimens collected from two areas, Sacca Degli Scardovari and Sacca Del Canarin, were co mpared for morphological characteristics of the gonads. The two lagoon s are characterized by different environmental and hydrographic factor s. Onset and development of the maturing stages was not identical in t he two lagoons suggesting a correlation between reproductive events an d different trophic conditions.