International audienceSize is the most important and valuable quality of the cultured black-lip pearl, Pinctada margaritifera. As this pearl aquaculture is carried out at numerous grow-out sites, this study analyzes the environmental influence on pearl size parameters (nacre weight and thickness) in relation to the recipient oyster biometric parameters (shell thickness, height, width, and oyster weight) at harvest time. Toward this end, an experimental graft was designed by using a homogeneous donor oyster phenotype. The recipient oysters were randomly and equally transferred and reared in five commercial and contrasting grow-out locations. Overall inter-site comparisons revealed that the cultured pearl size (N = 2168) and the biometric parameters of the recipient oysters were highest for sites with warmer temperatures with low seasonal variation in comparison to the southern latitude sites. These results were supported by positive correlations between pearl nacre thickness and recipient oyster shell thickness, height, and width. In parallel, the biomineralization potential of the mantle graft was screened through four genes encoding aragonite (Pif 177, MSI60) and calcite (shematrin 9, aspein). As the gene expression levels were the same among all the donor oysters, this finding demonstrates that: 1) the pearl sac that originated from the mantle graft was not isolated from environmental variations during the culture period and 2) the phenotypic expressions of the two biomineralizing tissues in the recipient oyster were consistent (shell and pearl). In the near future, this knowledge will be helpful at the production sites of genetically selected donor oyster lines for growth produced in hatchery systems. Culture site dependence on pearl size realization in Pinctada margaritifera in relation to recipient oyster growth and mantle graft biomineralization gene expression using the same donor phenotype. Available from: https://www.researchgate.net/publication/299384948_Culture_site_dependence_on_pearl_size_realization_in_Pinctada_margaritifera_in_relation_to_recipient_oyster_growth_and_mantle_graft_biomineralization_gene_expression_using_the_same_donor_phenotype [accessed Oct 18 2017]

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.