Illustration of a pearl in an oyster -

REX / Chameleons Eye / REX / SIPA

Scientists have just unraveled the enigma of the color of the pearl of the Polynesian oyster, known as the black pearl.

It is by going back to its genetic origin and by deciphering the ways of manufacture of pigments by the cells of the shell that the researchers were able to understand how the color of the pearl was formed, explains in a press release published on Monday the French Institute. research for the exploitation of the sea (Ifremer).

# Press release 🗞️ |

Scientists have finally unraveled the secret of the #Perle of the #Oyster from # Polynesia color, going back to its genetic origin!

➡️ Major results for the sector, to be discovered in 2 recently published articles 🤩


🔗 https://t.co/S8N6vIivmY pic.twitter.com/3pgF6ad3Vf

- Ifremer (@Ifremer_fr) March 22, 2021

A system based on a transplant

The production of farmed pearls is based on a graft between two oysters.

The graft comes from an organ in the donor oyster called the mantle.

It is a thin veil of flesh that ensures the growth and development of the shell.

The graft ensures the deposit of mother-of-pearl on a ball made from Mississippi mussel shells and inserted into the recipient oyster.

The color of the pearl is thus similar to that of the interior of the shell of the donor oyster.

"We have been able to identify the pigments that make the pearls red, yellow or green," explained Jérémie Vidal-Dupiol, epigeneticist at Ifremer and lead author of two recently published studies on the subject.

Scientists have discovered seven genes associated with pearl oysters with a yellow inner shell, nineteen in green and twenty-four in red.

"The differences in the color of the pearls are due to subtle nuances in the expression of this cocktail of genes", explains Pierre-Louis Stenger, researcher at Ifremer and one of the authors.

Depth also plays a role

According to the scientist, “these results are foundational for the future of pearl farming because they will facilitate the selection of animals for producers”.

"We could assay the expression of these genes in oysters that would be of interest in order to use them preferentially to make grafts", suggests Jérémie Vidal-Dupiol, stressing that until now the selection was "very empirical ".

But genetic makeup is not everything and the depth to which pearl oysters are raised can alter the expression of their genes.

"The deeper the oyster will be cultivated, the darker the pearl it will produce", adds Jérémie Vidal-Dupiol.

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  • Ifremer

  • study

  • Research

  • Oysters

  • Science