The influence of donor and recipient oyster red and blue shell nacre interference color on Pinctada fucata martensii pearl quality

Abstract

The influence of shell body color on pearls has been studied extensively, but the effect of shell interference color selection on pearls has not been fully understood yet. Because interference color is an important factor determining pearl quality, it is important to study whether the shell interference color of the donor and recipient oysters has any influence on the resulting pearls' interference color to cope with the market demands. We report that selective breeding of red- and blue-line Pinctada fucata martensii pearl oysters produce high-quality pearls based on shape, flaw, color, size, and luster assessment categories. Saibo from red- and blue-line donors was implanted with a rounded nucleus into the red- and blue-line recipient oysters from the same batch in four treatments which we refer to as DRMR (red-donor, red-recipient), DRMB (red-donor, blue-recipient), DBMR (blue-donor, red-recipient), and DBMB (blue-donor, blue-recipient) oysters. Pearl shape and flaws, body yellowness index (YI) and interference value color categories, luster value, total nacre and tablet thickness, and surface microstructure for these treatments are reported. More DRMR pearls are high grade (H) than DBMB, DBMR, and DRMB pearls. Using electronic pearl quality measuring devices, DRMR pearls have the lowest YI and highest interference color values, rendering them superior in color category. Whole nacre thickness of pearls estimated by the SEM on the pearl section reveal DRMR pearls have significantly (p < .001) thicker nacre than DBMB, DBMR, and DRMB pearls, rendering them generally larger in size. DRMR pearls also have significantly (p < .001) thicker nacre tablets in basal, middle, and surface regions of the nacre layer. Whereas luster does not differ significantly among treatments (p > .05), DRMR pearls are superior to those of other treatments in their shape, reduced number of flaws, color, and size. We consider that P. fucata martensii oysters with red shell nacre interference color improve pearl quality, and for the purposes of pearl culture should be selected for. These results are of commercial importance, especially where P. fucata is cultured for pearl production.