Freshwater pearl mussel

The freshwater pearl mussel (Margaritifera margaritifera) is an endangered species of freshwater mussel, an aquatic bivalve mollusc in the family Margaritiferidae. Although the name "freshwater pearl mussel" is often used for this species, other freshwater mussel species (e.g. Margaritifera auricularia) can also create pearls and some can also be used as a source of mother of pearl. Most cultured pearls today come from Hyriopsis species in Asia, or Amblema species in North America, both members of the related family Unionidae; pearls are also found within species in the genus Unio. The interior of the shell of Margaritifera margaritifera has thick nacre (the inner mother of pearl layer of the shell). This species is capable of making fine-quality pearls, and was historically exploited in the search for pearls from wild sources. In recent times, the Russian malacologist Valeriy Zyuganov received worldwide reputation after he discovered that the pearl mussel exhibited negligible senescence and he determined that it had a maximum lifespan of 210–250 years. The data of V. V. Zyuganov have been confirmed by Finnish malacologists and gained general acceptance. Subspecies within the species Margaritifera magaritifera include: Margaritifera margaritifera margaritifera (Linnaeus, 1758) Margaritifera margaritifera parvula (Haas, 1908) Margaritifera margaritifera durrovensis Phillips, 1928 – critically endangered subspecies in Ireland. Synonym: Margaritifera durrovensis. This subspecies is mentioned in annexes II and V of Habitats Directive as Margaritifera durrovensis. The freshwater pearl mussel is one of the longest-living invertebrates in existence. The oldest known specimen in Europe was caught in 1993 in Estonia when it was 134 years old. Like all bivalve molluscs, the freshwater pearl mussel has a shell consisting of two parts that are hinged together, which can be closed to protect the animal's soft body within. The shell is large, heavy and elongated, typically yellowish-brown in colour when young and becoming darker with age.