Comparison of harvested rate and nacre deposition parameters between cultured pearls issued from initial graft and second nucleus insertion inP. margaritifera

Abstract

Cultured pearls produced with Pinctada margaritifera, using the surgreffe method (implantation of a second nucleus following pearl harvest) were studied for the first time to: (1) examine family effect on nacre thickness, nacre weight and nacre deposition speed and (2) compare variation in these three traits with that obtained from the cultured pearls previously harvested after the corresponding initial grafts. A surgreffe experiment using 783 recipient oysters was realized in Rangiroa atoll (French Polynesia). After 24 months of culture, 389 cultured pearls were harvested. Significant donor family effect was found for the harvested pearl rate from surgreffe (P = 0.046). Highly significant donor family effect was recorded for nacre thickness (P = 0.004). Very highly significant donor family effects were recorded for nacre weight and nacre deposition speed (P < 0.0001). Comparison between surgreffe and initial graft showed: (1) no significant effect for the average cultured pearl rate harvested (P = 0.052) and average cultured pearl nacre deposition speed (P = 0.622) and (2) very highly significant differences (P < 0.0001) for the average cultured pearl nacre thickness and nacre weight. This study highlighted three major implications for pearl industry management: (1) donor family effect was maintained from initial graft to surgreffe, for nacre thickness, weight and deposition speed, (2) the persistence of the pearl sac metabolic activity over three years of culture and (3) the relation between harvested pearl rate and the size of the nucleus inserted in the pearl sac.

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

“…This metabolic activity consists of the secretion of an organic cell‐free matrix (proteins, glycoproteins, lipids and polysaccharides) on the nucleus surface by the external mantle epithelium (Rousseau, Plouguern, Wan, Wan, Lopez & Fouchereau‐Peron ). In addition, the maintenance of donor family effect via the pearl sac biomineralization process has been demonstrated to persist through the first graft culture period and the first surgreffe culture period (Demmer, Cabral & Ky ). The present study was the first on P. margaritifera to analyze the shell colour phenotypic criteria of donor oyster selection for pearl colour prediction and selective production (to fit to the international market demand).…”

Cost–benefit analysis of two culture methods that influence pearl production from the black‐lip pearl oyster, Pinctada margaritifera

“…A culture period of 18–24 months is then required to produce a cultured pearl with appropriate nacre thickness (Blay et al, ). Once a pearl is harvested by a technician, a second nucleus can be inserted in to the existing pearl sac, to produce a second pearl (Demmer, Cabral, & Ky, ; Kishore & Southgate, ). This “reseed” process, referred to as “surgreffe” in French Polynesia, can be performed up to four times assuming appropriate quality pearls continue to be produced by an oyster.…”

Variation in cultured pearl quality traits in relation to position of saibo cutting on the mantle of black-lipped pearl oyster Pinctada margaritifera

“…margaritifera recipients are often re-implanted to produce a second pearl (surgreffe) (Demmer et al, 2016;Kishore and Southgate, 2016). Saibo donors are carefully selected based on the visible quality (colour, lustre and surface quality) of their inner shell nacre, as the mantle tissue used to make the graft will influence the quality traits of resulting pearls (Alagarswami, 1987;Taylor, 2002), including for example their colour (Wada 1985;Wada and Komaru, 1996).…”