Abstract:This study compared the whole body weight, gender ratio, and fecundity of broodstcoks from two lines of Manila clam (Ruditapes philippinarum) with different shell shapes (wide-shell, WS and plate-shell, PS) and the growth and survival of their offspring. The results showed that the PS broodstock was larger than the WS broodstock (15.6 vs. 11.6 g/clam) (P＜0.05). The brookstock ♀:♂ratio was 0.62:1 for the PS line and 0.88:1 for WS line. Fecundity was 4.08×106 eggs/PS clam and 1.24×106 eggs/WS clam. There were no significant differences (P＞0.05) in sizes of eggs, D-larvae, and metamorphosed larvae between the two lines. The single-siphon juveniles of PS clams were larger (P＜0.05) in shell size than those of WS clams, while the double-siphon juveniles of the former were smaller (P＜0.05) than the latter. At the pelagic larval stage (0-16 days), there were no significant differences in the daily growth rate and survival of larvae between the two lines. During the metamorphosis (16-24 days), the daily growth rate of PS line ((3.91±067) μm d-1) was significantly greater (P＜0.05) than that of WS line ((2.64±0.34) μm d-1). The metamorphosis rate of the former (15.68%±3.06%) was also higher than that of the latter (5.32%±1.53%) (P＜0.01). During the indoor (24-60 days) and outdoor (60-180 days) rearing periods, the PS line also grew faster and had higher survival than the WS line (P＜0.05). These results indicate that the PS line appears to be superior to the WS line in most production traits evaluated.