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des Tuamotu, France

Blay C.,Center du Pacifique | Sham-Koua M.,Center du Pacifique | Vonau V.,Center du Pacifique | Tetumu R.,Center du Pacifique | And 2 more authors.
Aquaculture International

Cultured pearl nacre deposition rate in Pinctada margaritifera oysters was studied to examine its influence on Tahitian classification grade and colour and to further our understanding of using selected donor oysters produced in a hatchery system for the improvement of these traits. A large-scale grafting experiment using 150 farmed donor oysters was realised in Rangiroa atoll (French Polynesia). After 18 months of culture, 874 pearls were harvested and 7 pearls quality traits were recorded: (1) nacre deposition rate assessed by nacre thickness and weight, (2) classification grade, lustre and surface defects, and (3) colour assessed by pearl colour darkness level and visual colour categories. Nacre deposition rate significantly influence pearl grade, surface defects, darkness level and colour categories, but not the lustre. Grade A pearls had the thickest and heaviest nacre on average, compared with grade D pearls and rejects. In addition, pearls without any surface defect had thicker and heavier nacre. Pearls with low darkness were the thinnest and the lightest. Pearls of aubergine-peacock secondary colours were the thickest and the heaviest. These results highlight the importance of rapid nacre deposition rate for increasing the production of grade A pearls, with less surface defects and dominance of a black tone colour. Fast nacre deposition may, however, have a negative impact on other pearl quality traits, such as pearl lustre. This study demonstrates the importance of examining relationships between pearl quality traits in a way that provides solid information that can be directly used for breeding and genetic selection programmes. © 2013 Springer Science+Business Media Dordrecht. Source

Blay C.,Center du Pacifique | Blay C.,CNRS Insular Research Center and Environment Observatory | Parrad S.,Center du Pacifique | Cabral P.,Love Here Pearl Farm | And 2 more authors.
Estuarine, Coastal and Shelf Science

The black-lipped pearl oyster, Pinctada margaritifera, produces the largest and most valuable coloured pearls in the world. Cultured pearl size remains one of the most important quality traits. Despite the great geographical area covered by pearl farms in the atolls of French Polynesia, little is known about the influence of grow-out site effects on pearl size attained. To explore the genetic and environmental impact on the size of pearls as well as the genetic × environment interaction, a uniform experimental graft was designed on two contrasting macro-geographical lagoons. Five biparental families of donor oysters were grafted and then reared at both sites. After 18 months of culture, phenotypic parameters corresponding to pearl size, i.e. nacre weight and thickness, were recorded among the harvested pearls. The expression of Pif-177 gene, a biomarker encoding protein in the aragonite nacreous layer, was analysed in the corresponding pearl sac. The results show a family effect for nacre weight and thickness on both sites, with family F058 producing the heaviest and thickest nacre, and F805 the lightest and thinnest. By contrast, inter-site comparison revealed no significant site effects for these two parameters. In addition, grow-out location did not modify the relative gene expression of Pif-177 in the pearl sac between donor families in either culture site. Both nacre weight and thickness were positively correlated with the level gene expression of Pif-177. These results suggest that pearl size parameters were not affected by the environment in the present study and this is supported by the relative gene expression of Pif-177 observed. This knowledge constitutes an initial step in the study of pearl size trait inheritance, which will be helpful in the near future for the diffusion of genetically selected donor oyster lines produced by hatchery systems throughout production sites. © 2016 Elsevier Ltd. Source

Ky C.-L.,Center du Pacifique | Demmer J.,Center du Pacifique | Sham-Koua M.,Center du Pacifique | Cabral P.,Gauguins Pearl Farm
Journal of Shellfish Research

Production of larger, rounder, high-quality cultured pearls with fewer circles is one of themain challenges of Pinctada margaritifera aquaculture faced by every pearl farm in French Polynesia. Although bigger pearl sizes can be achieved through surgreffe operations (implantation of a second nucleus after pearl harvest), control of the development of pearl circles and shapes still remains unclear, as illustrated by grafter's empirical rules, where often the surgreffe process is only performed after production of uncircled and round pearl shapes. The present study was designed with a real pearl by pearl traceability to reveal for the first time the development of circles and shapes from graft and surgreffe, in relation to the size of the pearl sac. This was indirectly assessed by measuring the differences in diameter (DD) and weight (DW) between standardized surgreffe nuclei and the pearl that had been harvested after the initial graft.An experimental graft and surgreffe experimentwas designed using the same criteria: grafter, location, nuclei brand and size for graft and surgreffe, and donor oysters from 10 biparental families produced in a hatchery system.We studied the differences between pearls harvested after graft and surgreffe on the same recipient oysters (n=295 for both graft and surgreffe) in relation to three classes of DDand DWin which the surgreffe nuclei, were: (1) bigger/heavier, (2) equivalent to, or (3) smaller/lighter than the harvested pearl. Results revealed that to increase the rate of uncircled pearls after surgreffe, insertion of a nucleus larger than the harvested pearl may be advisable. Indeed, the formation of uncircled pearls after surgreffe was enhanced by inserting bigger/ heavier second nucleus, both in animals that had produced a uncircled pearl after the initial graft and in those that had produced a circled pearl. For pearl shape, significantly more round shape pearls were produced after surgreffe, after initial oval and baroque samples from graft, by inserting smaller/lighter and bigger/heavier second nucleus, respectively. Inserting a larger second nucleus will significantly increase the rate of both uncircled and round-shaped pearls. This finding has important implications for surgreffe practices, where recipient oysters with undesirable circle or baroque pearls could now be used in this second stage of production. Source

Ky C.-L.,French Research Institute for Exploitation of the Sea | Blay C.,French Research Institute for Exploitation of the Sea | Sham-Koua M.,French Research Institute for Exploitation of the Sea | Vanaa V.,French Research Institute for Exploitation of the Sea | And 2 more authors.
Aquatic Living Resources

Individual Pinctada margaritifera molluscs were collected from the Takapoto atoll (Tuamotu Archipelago, French Polynesia) and used to produce ten first generation full-sib families in a hatchery system, following artificial breeding protocols. After three years of culture, these progenies were transferred to Rangiroa atoll (Tuamotu Archipelago, French Polynesia) and tested for their potential as graft donors. A large-scale grafting experiment of 1500 grafts was conducted, in which a single professional grafter used ten individual donor oysters from each of the ten families, grafting 15 recipient oysters from each donor. The recipient oysters were all obtained from wild spat collection in Ahe (Tuamotu Archipelago, French Polynesia). After 18 months of culture, 874 pearls were harvested. Highly significant donor family effects were found for nucleus retention, nacre thickness, nacre weight, pearl colour darkness and visually-perceived colour (bodycolor and overtone), pearl shape categories, surface defects and lustre, the last two of which are components of the Tahitian classification grade. No significant difference was recorded between the ten G1 families for the absence or presence of rings. The progenies could be ranked from "best" (i.e., the donor whose grafts produced the greatest number of grade A pearls) to the "worst". Some progenies had extreme characteristics: family B presented the greatest number of pearls with lustre (98%) and a high proportion of dark gray to black with green overtone pearls (70%). These results have important implications for the selective breeding of donor pearl oysters: it may be possible to reach a point where specific donor lines whose grafts produce pearls with specific quality traits could be identified and maintained as specific breeding lines. © EDP Sciences, IFREMER, IRD 2013. Source

Ky C.-L.,French Research Institute for Exploitation of the Sea | Blay C.,French Research Institute for Exploitation of the Sea | Sham-Koua M.,French Research Institute for Exploitation of the Sea | Lo C.,Direction des Ressources Marines et Minieres | Cabral P.,Gauguins Pearl Farm

The top aquaculture species in French Polynesia is Pinctada margaritifera, a mollusc grown for the production of a unique gem: the black pearl. One of the challenges facing the pearl farming industry is to "produce less but better pearls" through genetic improvement. An experimental hatchery system was used to generate full-sib families to be tested for their potential as donor "oysters". A large-scale grafting experiment was done and seven cultured pearl quality traits: grade, surface defects, lustre, darkness level, visual colour categories, circles and shape categories were recorded. Our results revealed, for the first time, significant phenotypic relationships between these quality traits. The grade A cultured pearl class had the largest proportion of pearls with a green overtone (65%), the lowest number of circled pearls (15%) and the maximum of round-shaped pearls (45%). In contrast, the "reject" cultured pearl class had the largest proportion of pearls with grey body color (65%), the greatest number of circled pearls (35%) and the maximum with a baroque shape (nearly 60%). When grade components were studied separately, cultured pearls in the zero surface defect class exhibited the same tendencies as grade A pearls, contrasting with the class where there were more than ten defects on the surface of each pearl. When cultured pearls were classified according to the presence or absence of lustre, pearls with lustre mostly had a green overtone colour, whilst pearls without lustre did not. These findings have major implications for cultured pearl quality improvement, as modern genetic breeding methods can increase the proportion of high quality cultured pearls though selected lines of donor oysters capable of producing pearls with a green overtone. Selection of appropriate donor phenotypes, incorporation of pigmentation traits into a pearl oyster breeding programme and production of lines with desirable colours will be developed for oyster aquaculture in French Polynesia. © 2014 Elsevier B.V. Source

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