Inbreeding Depression on Growth and Survival of Full-Sib Family of Manila Clam (Ruditapes philippinarum)

In present study, the inbreeding depression (ID) of growth and survival of Manila clam (Ruditapes philippinarum) was investigated at larval and juvenile stages. Nine inbred families (A2, B2, C2, D2, E2, F2, G2, H2 and I2) were established by mating within nine full-sib families with expected inbreeding coefficient of 0.25. Inbred families showed significant differences in shell length and hatching rate of D-larvae (straight-hinged larvae). The larvae of the nine inbred families grew slower than those of control group (CG), and their ID value ranged from 0.81% ± 6.09% to 16.10% ± 1.49%. The ID value of larval survival rate varied between 27.47% ± 9.36% and 70.50% ± 13.66%. The ID was also detected for juvenile growth in A2, B2, C2, and D2, which ranged from 4.60 ±2.21 to 17.71 ± 7.73. The A2 family maintained the highest juvenile survival rate, whereas the other inbred families exhibited ID values varying between 62.79% ± 4.54% and 96.14% ± 0.87%. The linear relationship of estimated ID between growth and survival was negatively correlated (R = ?0.434, P < 0.05). The results of this study suggested that the ID of growth was common at the larval stage but was less prevalent at juvenile stage. In contrast, the ID of survival increased from larval to juvenile stage. A better understanding of the effect of inbreeding may aid to selective breeding of Manila clam.