A comparison of growth and development of Manila Clam (Ruditapes philippinarum) from two pedigrees

Two pedigrees of manila clam(Ruditapes philippinarum)were established on the basis of shell colors in 2004.The pedigrees were Zebra variety with zebra-like color patterns on the shell,and Liangdao Red with two bright red radioactive strips on shells.The shell length of D-larvae,larval growth,survival,metamorphosis and growth and survival at juvenile and grown-out stage were compared for the different manila clam pedigree.The results show that the differences of shell lengths of D-larvae between the Zebra pedigree breed and Liangdao Red pedigree breed and between Liangdao Red pedigree breed and control group were significant.However,no evident difference of shell lengths of D-larvae between the Zebra pedigree breed and control group were found.The shell lengths of Zebra pedigree and Liangdao Red pedigree were larger than that of control group at days 4 and 7.The differences of survival at day 4 among all groups were not significant.The differences of the metamorphosis among all groups were significant.The shell lengths of the Zebra pedigree breed at days 24 and 66 were larger than those of Liangdao Red pedigree and control group.The significant difference of shell length between Zebra and Liangdao Red pedigree was not observed.At day 135,the shell length of Liangdao Red pedigree breed was significantly larger than that of Zebra pedigree and the shell length of Zebra pedigree breed was significantly larger than that of the control group.The survivals in both nursing and grown-out stage were ranged in a descendant order as the following: zebra group control group Liangdao Red group.At day 393,the shell length of Liangdao Red pedigree was significantly larger than those of Zebra pedigree breed and control group.