The "'glochidium "'( plural "'glochidia "') is a microscopic larval stage of some freshwater mussels, aquatic bivalve mollusks in the families Unionidae and Margaritiferidae, the river mussels and European freshwater pearl mussels.
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Like all molluscs, the freshwater pearl mussel has a muscular'foot'; this very large, white foot enables the mussel to move slowly and bury itself within the bottom substrate of its freshwater habitat.
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It remains an area of outstanding natural beauty, with a diverse ecological system and wide variety of plants, birds and fish, including freshwater pearl mussel, Atlantic salmon, whooper swans, kingfishers and otters.
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The project aims to conserve the species at 21 sites in the UK . The freshwater pearl mussel relies for part of its life on the presence of salmonids, a group of fish including salmon and trout.
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The main commercial sources of mother of pearl have been the pearl oyster, freshwater pearl mussels, and to a lesser extent the abalone, popular for their sturdiness and beauty in the latter half of the 19th century.
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One family of nacreous pearl bivalves the pearl oyster lives in the sea, while the other a very different group of bivalves lives in freshwater; these are the river mussels such as the freshwater pearl mussel.
