Is pearl colour produced fromPinctada margaritiferapredictable through shell phenotypes and rearing environments selections?

Abstract

The black-lipped pearl oyster, Pinctada margaritifera, is the most important farmed mollusc species in French Polynesia. Donor oyster selection among wild P. margaritifera individuals, chosen according to their inner shell colour, makes it possible to obtain the broadest range of cultured pearl colours of any species. This study demonstrates the relative influence of using black [B] or red [R] outer shell phenotypes, combined with green [G] or yellow [Y] inner shell phenotypes, on pearl darkness level, colour categories and lustre. A large scale grafting experiment was designed and carried out over five grow-out locations, covering three archipelagos: Tuamotus, Society and Gambier. Results revealed that the [B + G] phenotypes may be used as donors to produce dark green pearl, which suit the demands of the Asian market; whereas, phenotypes incorporating [R] and/or [Y] phenotypes may be used to obtain multicolour pearls of medium/light darkness, which suit the demands of the European market. From an environmental point of view, the 1) [B] phenotype showed no significant variation for light and other pearl colour production, and 2) [Y] phenotype produced both the same rate of pearl darkness level and green colour pearls whatever the grow-out location. A classification tree model was built to predict, according to shell phenotype and culture location, the colour and darkness level of harvested pearls. Lustre was shown to be more influenced by the environment than by phenotype. These results should be taken into account in pearl farm production management and in selective breeding programmes.

Age-dependence of cultured pearl grade and colour in the black-lipped pearl oysterPinctada margaritifera

“…In addition, a study of the digital colour of P. fucata martensii has shown that the nacre colour of the donor oysters contributes to the resulting pearl colour (Gu, Huang, Wang, Gan, Zhan, Shi & Wang ). Recently, the pearl colour in P. margaritifera was demonstrated definitively to be related to the inner shell phenotype colouration of the donor (Ky, Le Pabic, Sham‐Koua, Okura, Molinari, Nakasai & Devaux ). For the same wild spat collection location, frequency of colourful inner shells was higher in young individuals than in older ones.…”

The Mendelian inheritance of rare flesh and shell colour variants in the black‐lipped pearl oyster (Pinctada margaritifera)

“…More recently, Ky et al . () also revealed correlations between the outer and inner shell colours of donors and the colour proportions observed in the harvested pearls. Whereas shell morphology is a species‐specific characteristic, shell colour varies very widely among P. margaritifera individuals used as donors, allowing the production of an equally broad spectrum of pearl colours.…”

Mono- and polychromatic inner shell phenotype diversity in Pinctada margaritifera donor pearl oysters and its relation with cultured pearl colour

“…Although only a few studies have been made on transmissions between donor phenotypes and pearl colours in P. margaritifera, these relations have been demonstrated through experimental grafting designs using both wild (Tayale et al, 2012) and hatchery-produced (Ky et al, 2013;2016a) donor oysters. More recently, Ky et al (2015a) also observed correlations between the outer (prismatic layers) and inner (nacreous layers)…”