Mono- and polychromatic inner shell phenotype diversity in Pinctada margaritifera donor pearl oysters and its relation with cultured pearl colour
Résumé
The pearl oyster Pinctada margaritifera has the specific ability to produce pearls with the widest range of colours
among all pearl oyster species. This pearl colour diversity originates from the mantle biomineralising tissue
(graft) of the donor oyster, which is originally responsible for the variety of colours of the inner shell surface.
This study aimed to: 1) assess the geographic distribution and establish a first stocklist of the colourful oyster
phenotypes used as donors in French Polynesia, and 2) investigate the phenotypic relation between inner shell
colouration and the corresponding colour of harvested pearls. With the support of a pearl farmers' network,
we investigated the different donor phenotype frequencies among five collection sites (Ahe, Apataki, Takaroa,
TakumeandMangareva). This donor evaluation was made during grafting of pearl oysters (N=49,938) obtained
from collector stations. Results showed that pearl production is mainly based on six common colourful donor
phenotypes classified as monochromatic and polychromatic profiles, which shown different frequencies
among the collection sites. Experimental grafts (N=4640)were then realised and subsequent culture conducted
at a single site in order to avoid pearl colour variation due to environmental influences. Traceability between donors
(N=232) and pearls (N=2776), revealed that: 1) yellow (gold) and aubergine (reddish) pearls could be
mostly obtained by using the monochromatic yellowand red donor phenotypes, respectively, and 2) one third to
one quarter of grey pearlswas inevitably harvested, whatever the polychromatic phenotype chosen as the donor,
which leaves at least half the harvest composed of the attractive green and peacock colours. This preliminary
stocklist of colour range together with analysis of the colour phenotype transmission between inner shell and
pearl provide the basis for producing multiple pearl oyster “colour lines” through hatchery propagation and
would be helpful for future selective breeding programs.
Statement of relevance: Donor shell colour selection predict colours of pearls