Inheritance of shell pigmentation in Pacific oyster Crassostrea gigas

The Pacific oyster (Crassostrea gigas) is one of the most important species which has the largest production among all cultured shellfish. Recently, several shell color strains of C. gigas have been developed to improve the commercial values, however the inheritance of shell pigmentation is still unclear. A total of 29 families cross-mated between different pigmented oysters were produced to investigate the inheritance of the shell pigmentation and purple pigmentation. Random samples from each family were obtained and their shell pigmentation were recorded. Results revealed that shell pigmentation was controlled by two genetic locus, among which one is responsible for secretion of pigmentation and the other is responsible for distribution mode of pigmentation. The locus controlling the secretion of pigmentation has two alleles with the allele for the presence of pigmentation being dominant to the allele for the absence of pigmentation. Similarly, another locus controlling the distribution mode of pigmentation has two alleles with the allele for striped distribution being dominant to the allele for solid distribution. In addition, one independent locus with two alleles was suggested to control the purple-striped pigmentation, which one allele for shell devoid of purple pigmentation is dominant to another allele for shell with purple pigmentation. The findings will provide valuable information for the efficient selective breeding of shell color strains in the Pacific oyster.