DNA techniques applied in the identification of Pinctada fucata pearls from Uwajima, Ehime, Japan

Abstract

The DNA technique is a useful method to apply in the identification of pearl species, providing it is possible to extract DNA from the tiny quantities removed from solid pearl samples. Meyer et al. (2013)¹ reported on a method used to identify the pearl oyster species Pinctada margaritifera, P. maxima, and P. radiata. In order to take this a step further, DNA methods were applied to P. fucata mollusks and their pearls in this study. On-site sampling was performed during Hamaage (harvesting) at Uwajima, Ehime prefecture, Japan, in January 2016. Twenty-eight pearl oysters used for culturing, the thirteen cultured pearls and two keshi pearls they contained, and nine donor oysters were collected. 16S rRNA extraction from mantle tissues was performed using a general phenol-chloroform extraction method, while 16S rDNA from the pearl samples were obtained using a similar destructive method to that described in Meyer et al. (2013)¹. Both 16S rDNA genes extracted from mantle tissues of one donor shell and one pearl-culturing shell were fully matched with the complete sequence of P. fucata². 16S rRNA genes extracted from the powder of four pearl samples were also found to match the sequence of P. fucata, though one recovered sequence was 350 bp. Thus the oyster and pearl samples from Uwajima, Ehime, Japan obtained in January 2016 were categorically identified as P. fucata species. From a methodology point of view, even after using the destructive method, it was possible to determine P. fucata 16S rRNA gene from only 5 to 10 mg of pearl powder sample weight compared to the previously reported quantities of pearl powder required (13 to 100 mg)¹.