Press Release

March 11 , 2013

Incorporated Administrative Agency, Fisheries Research Agency

A 100-year-old mystery about pearls was finally solved
-The first scientific evidence revealing the principles of the Japanese pearl culture technology-

  • The technology of pearl culture by implanting a piece of mantle tissue together with a bead into another oyster was developed in Japan, but the scientific basis was unclear.
  • The study team analyzed genes related to pearl formation, and for the first time in the world, verified that the implanted tissue continues living in the recipient, taking a big part in pearl formation.

The epoch-making technology of producing cultured pearls was developed in Japan more than 100 years ago and is widely used today. It involves excising a piece of mantle tissue from a Japanese pearl oyster (Pinctada fucata martensii) and implanting the graft together with a bead into another oyster to induce pearl sac formation around the bead. However, it has been a mystery whether or not the implanted graft continues living in the recipient and takes a part in formation of the pearl, because it has been difficult to confirm.

The Fisheries Research Agency, Azabu University and Mie Prefecture Fisheries Research Institute jointly investigated the genes involved in pearl formation and confirmed that the genes of the donor oyster were expressed even 18 months after the implantation. By this, the study team demonstrated the principle, which had been unverified for more than 100 years.

The study results show that the implanted mantle tissue continues existing in the recipient and takes a part in the pearl formation. The team will search for genes related to good-quality pearls, such as high degree of luster, good color and thick nacre, to culture high-quality pearls.

The study results were published in Aquaculture, Volumes 384-387, pp. 56-65 (

Fig. 1 Shell, pearl, and mantle of Pinctada fucata martensii. The mantle produces the shell.