Development of Cultured Pearl Circles and Shape after Initial Graft and Second Nucleus Insertion in the Black-Lipped Pearl OysterPinctada margaritifera

Abstract

ABSTRACT 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 usin...