<img src="https://img.lemde.fr/2023/09/08/0/0/4368/2912/664/0/75/0/209433d_1694184079487-bios-2449777.jpg" srcset=" https://img.lemde.fr/2023/09/08/0/0/4368/2912/556/0/75/0/209433d_1694184079487-bios-2449777.jpg 556w, https://img.lemde.fr/2023/09/08/0/0/4368/2912/600/0/75/0/209433d_1694184079487-bios-2449777.jpg 600w, https://img.lemde.fr/2023/09/08/0/0/4368/2912/664/0/75/0/209433d_1694184079487-bios-2449777.jpg 664w, https://img.lemde.fr/2023/09/08/0/0/4368/2912/700/0/75/0/209433d_1694184079487-bios-2449777.jpg 700w, https://img.lemde.fr/2023/09/08/0/0/4368/2912/800/0/75/0/209433d_1694184079487-bios-2449777.jpg 800w" sizes="(min-width: 1024px) 556px, 100vw" alt="A hollow oyster (" crassostrea="" gigas"),="" on="" the="" dutch="" coast."="" width="100%" height="auto">
Oyster enthusiasts are a fairly widespread species. Willing to travel hundreds of kilometers to enjoy a coastal platter, they place the mollusc above all else. Some will quote La Fontaine or Lewis Carroll, while others will tell you that ancient Athenians used shellfish to vote, giving rise to the verb "to ostracize." Above all, they are generally experts on everything to do with the cultivation and consumption of Crassostrea gigas, the Japanese oyster, better known as the Pacific oyster.
Of the 66 or so known species, the Pacific oyster alone accounts for 98% of the 130,000 metric tons produced each year on the French coast. That's a far cry from the 3.7 million metric tons farmed by the Chinese, but it still represents 90% of European production. Why a Japanese oyster on the Atlantic coast? Quite simply because, after centuries of uneventful consumption, the flat oyster was decimated by a pathogen in the 1930s. Producers then turned to the Portuguese oyster, which in turn succumbed to infection in the 1970s. This time, oyster farmers went as far as the Far East to find a resistant mollusc. But, once again, this sought-after solution came under attack. Dubbed POMS (Pacific Oyster Mortality Syndrome), this viral disease first appeared in the early 2000s. At first, it remained discreet. But in 2008, a new variant turned this little nuisance into a serial killer, wiping out 40% to 100% of affected larvae.
Scientists then set to work. First, they realized that the herpes virus in question was attacking the bivalve's immune system, leaving it defenseless against opportunistic infections. They then studied this lethal phenomenon to try and understand how certain individuals, often entire colonies, managed to resist it. In an article published on Friday, September 8, in Science Advances, a team from the Host-Pathogen-Environment Interactions (IHPE) laboratory in Montpellier provided the answer: Resistant molluscs underwent "rapid adaptation" thanks to a few appropriate genetic mutations and, above all, epigenetic changes.
For seafood lovers unfamiliar with the intricacies of molecular biology, it's worth noting that epigenetics isn't concerned with the genetic code and the nature of the proteins it synthesizes, but with the activity of genes, their "expression," which can be strengthened or weakened by certain small chemical additions to the DNA. "Our study has highlighted the crucial importance of these epigenetic modifications, sometimes in conjunction with genetic mutations, but sometimes in the absence of any mutation at all," emphasized Jérémie Vidal-Dupiol, researcher at the Institut Français de Recherche pour l’Exploitation de la Mer (IFREMER, state-run oceanographic institution) and coordinator of the study.
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