Genetics of Shell Color and Pattern in the Bay Scallop Argopecten irradians

The bay scallop Argopecten irradians is polymorphic for background color of the shell, which may be orange, yellow, or white, and is also highly variable for the distribution of overlying dark pigments. In one series of variations, the pigments may occur on the left (top) valve only, both valves, or neither. The results of self-fertilized matings demonstrate that background color is controlled by one gene with orange and yellow dominant to white. The color locus appears to show dominant epistasis to one or more genes that determine the distribution of overlying pigments.