Growth and nutritional differences between two shell-color clams (Cyclina sinensis)

Shellfish shell color often exhibits polymorphism, and shell color can be used as a marker color for excellent trait and used in the breeding of improved shellfish species. In order to explore the relationship between shell-color trait of clam Cyclina sinensis and its growth and nutritional components, we measured and analyzed the growth indicators and nutritional components of individuals with different shell colors. The results showed that the wet weight, shell length, wet weight of pipes and gills of the purple-shell individuals were significantly higher than those of the white-shell individuals (P<0.05), and shell width and wet weight of mantle tissue were extremely significantly higher than those of white-shell individuals (P<0.01). The content of crude fat and crude protein of the edible parts from purple-shell individuals were extremely significantly higher than those of the white-shell individuals (P<0.01). The ratios of essential amino acids to total amino acids in purple- and white-shell individuals were 37.46% and 37.02%, respectively, and this ratio of purple-shell individuals was significantly higher than that of white-shell individuals (P<0.05); the ratios of essential amino acids to non-essential amino acids were 67.72% and 66.60%, and this ratio of purple-shell individuals was significantly higher than that of white-shell individuals (P<0.05), indicating that the amino acid balance effect in the purple-shell individuals was better than that of white-shell individuals, and they were all high-quality proteins. The monounsaturated fatty acids of purple- and white-shell individuals are mainly palmitic acid, accounting for 9.97% and 9.85% of the total fatty acids, respectively; Polyunsaturated fatty acids mainly consist of EPA and DHA, of which EPA accounts for 6.64% and 6.54% of the total fatty acids in purple- and white-shell individuals respectively, and DHA accounts for 8.00% and 8.51% of the total fatty acids respectively. Taken together, it suggests that there are certain differences in growth and nutrition between purple- and white-shell individuals and a certain positive relationship between purple shell traits and their growth and nutrition, which provides a theoretical basis for using purple-shell trait as genetic marker in clam breeding.