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RESEARCH PRODUCT

"Save Private Pinna !" The Mediterranean fan mussel, a patrimonial bivalve, is in serious danger of extinction.

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Pinna nobilis is the largest bivalve in the Mediterranean Sea. This endemic species lives in the Posidonia meadows,in the form of small sparse populations. It is a heritage species: its byssus has long been collected to be wovenand used to make gloves, hats or stoles. Protected by a European Directive (1992), P. nobilis is closely monitored,nationally and internationally. But since the end of 2016, an epidemic, which origin seems to be a protozoan parasite,decimates populations (up to 100% mortality). This event began on the Spanish coast and spreads now all around theMediterranean. Although conservation measures have been taken, the next few years could see the extinction of thisemblematic bivalve. Apart from its symbolic value, P. nobilis is a species worthy of biotechnological interest. Its shellcomprises two mineralized layers, one of which, external, calcitic, consists of large monocrystalline prisms, consideredas a model in biomineralization. Understanding their formation and growth is a challenge in biomimetics. Its byssusforms very fi ne remarkably solid fi laments, with ultrastructural properties different from those of the mussel byssus.Until now, the chemistry of this byssus remains mysterious. Understanding it is also a challenge in material physics.These different points are discussed in this article.