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

Abstract

Cultured pearl production from Pinctada margaritifera uses the biomineralization capacities of the mantle graft, the saibo, which is usually obtained from only the middle mantle section of the donor oyster. To evaluate the potential for using other parts of the mantle, this study explores and describes the cultured pearl quality traits, pearl size, shape, surface defects and colour parameters obtained with saibo from the entire length of the mantle, comprising the four following sections: 1) posterior, 2) connection with the gills, 3) middle, (the section usually used commercially), and 4) anterior. Rates of nucleus retention and oyster mortality were also recorded and compared between sections. For this, two experimental grafts were designed and conducted in two contrasting culture sites, using 10 selected wild donor oysters in each to perform a total of 1536 grafts. Mantle section comparison revealed that the anterior section was different from the three other sections, showing: 1) the lowest nacre deposition rate in terms of weight and thickness, 2) the palest pearls, with lowest rate of the attractive overtone colour and the 3) a lower rate of pearls with lustre. For pearl circles and shape, no difference was recorded among the different mantle sections. Posterior, connection and middle sections showed similar pearl quality traits, revealing how the number of high quality saibo obtainable from the same batch of donors can easily be increased, thus benefitting the P. margaritifera pearl industry. This finding could provide significant benefits to pearl farmers and the further development of current pearl grafting practices. Highlights ► Pearl quality traits variations were for the first time explored using all saibo position from the four mantle sections. ► The posterior and connection zone could be used to produce pearls with similar pearl quality traits as the middle section. ► The number of saibo obtainable from rare colourful wild donors could be increase.

Whole transcriptome sequencing and biomineralization gene architecture associated with cultured pearl quality traits in the pearl oyster, Pinctada margaritifera

“…A considerable number of studies have focused on the identification of genes involved in aragonite and/or calcite formation in pearl oyster species and other bivalves capable of shell mineralisation [20, 22, 46, 47, 48–54]. Nonetheless, it has proven difficult to extrapolate the role of key actors involved in determining cultured pearl quality across studies.…”

“…A recent study in P. margaritifera , based on controlled bi-parental crosses and the F1 generation, demonstrated heritability ( h 2 from 0.21 to 0.37) for nacre weight and thickness, pigmentation darkness and colour, surface defects and grade, signifying a donor oyster effect with a genetic basis, although there were also important interaction components [10]. Previous studies reported that location, temperature and food availability [11–13], pearl rotation [14], donor oyster genotype [4, 9, 15–18], age [19], position of graft mantle [20] and contamination during the graft operation and/or graft operator skills [21] are all determinants of final pearl quality and do not necessarily affect similar traits.…”

Relationship of the orange tissue morphotype with shell and pearl colouration in the mollusc Pinctada margaritifera

“…The capacity of P. margaritifera to produce pearl colours overlapping the colour ranges of pearls of two other rival species is related to donor shell phenotypic diversity. This donor influence is observed not only at an inter-individual scale 13 but also at an intra-individual level, through effects of the position on the donor mantle at which the graft is cut 14 .…”