Effects of nucleus position, profile and arrangement on the quality of mabe pearls produced by the winged pearl oyster, Pteria penguin

The position and arrangement of nuclei is the most important technical aspect of mabe pearl (half-pearl) production. This study examined the effects of nucleus arrangement, profile (height) and position, on quality, nacre thickness and shape of mabe pearls produced by Pteria penguin. Oysters implanted with three nuclei produced a greater proportion of saleable mabe pearls with more regular shapes than oysters implanted with five nuclei. Use of low profile nuclei resulted in mabe pearls with increased nacre thickness and produced mabe pearls of significantly higher quality, with more regular shapes than high profile nuclei. Nucleus position significantly influenced mabe pearl quality, nacre thickness and shape. The posterior-ventral position of the left shell valve produced mabe pearls of the highest quality with the thickest nacre and was the best location for mabe pearl culture. Based on the results of this study, it is recommended that P. penguin is implanted with a maximum of three nuclei to increase the production of regular-shaped mabe pearls, and that low profile nuclei are used to improve quality and nacre thickness of mabe pearls produced in less favourable nucleus positions. An optimal nucleus arrangement for P. penguin of 130-150 mm dorso-ventral height would include one high profile nucleus in the posterior-ventral position of the left shell plus additional low profile nuclei in both the anterior-ventral position of the left shell valve and, the center of the right shell. Based on the quality grading system used in this study, a minimum commercial nacre thickness of 0.25 mm is recommended for mabe pearl production using P. penguin.