Evidence for genetic control of pigmentation of shell and mantle edge in selected families of Pacific oysters, Crassostrea gigas

Three experimental cohorts of pedigreed oysters, each having gone through one or two generations of selection, were investigated for both shell and mantle edge pigmentation. Initial investigations showed the traits to be complex and best described as continuous. Average intraclass correlations coefficients (t) for all three cohorts of 0.766 and 0.666 (n=75) were obtained for shell and mantle edge pigmentation, respectively, indicating a high degree of genetic control. Block effects (depth at planting) were also significant in some cases, though trends were less obvious, and these effects only accounted for a maximum of 7.6% of the total observed phenotypic variation. Mantle edge pigmentation and shell pigmentation were positively correlated (P<0.0001, r=0.578, n=45), however, this correlation was statistically significant in only two of the three cohorts (P<0.4994, r=0.193, n=15). The performance traits of average family individual body weight (g), survival (%), and yield (kg bag−1) were not correlated with mantle edge or shell pigmentation (P>0.09, n=75) in all but two cases (P=0.0400 and P=0.0359, n=75). This is the first report of a genetic effect on shell and mantle pigmentation in Crassostrea gigas. These findings have major implications for the manipulation of pigmentation as a desired trait in an oyster breeding program.