Estimation of genetic parameter for shell strength trait in the razor clam Sinonovacula constricta

The razor clam Sinonovacula constricta, one of the most widely cultivated mollusks in China, is characterized by thin shells and high meat yield compared with other mollusks. However, the weak shell often caused huge shell-damage and even death events in some commercial activities, such as aquaculture management, harvest, transportation and clam grading. Selective breeding focusing on shell strength could be an imperative and effective approach to solve the problem, though the genetic framework underlying the trait is currently unknown. In the present study, we estimated the heritability of shell strength and growth traits using 33 full-sib families (1129 individuals) by the animal model in S. constricta. A high level of phenotypic variation in shell strength was documented within families, and the trait obeys continuity variance and normally distributed in S. constricta. Genetic analysis demonstrated that shell strength exhibited moderate heritability (0.33 ± 0.09), while the heritability of growth traits (shell length, shell height, shell width and body weight) was in moderate to high level, ranging from 0.36 ± 0.09–0.63 ± 0.12. On the other hand, there were comparatively low genetic correlations between shell strength and growth traits (0.13 ± 0.21–0.50 ± 0.17), indicating that a significant improvement of shell strength cannot be obtained simply through selection for growth. Instead, shell strength should be specifically incorporated into the selection index using a family-based breeding program, as shell strength measurement is destructive. In summary, we explored the possibility of genetically improving the shell strength trait through breeding program by examining this trait’s genetic basis. The existence of genetic variation for shell strength trait was elucidated. Moderate heritability and moderate magnitude of genetic correlations with growth traits were documented about the trait. Consequently, the shell strength of S. constricta should be effective in obtaining genetic improvement through breeding programs under commercial conditions.