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Margaritifera auricularia is a species of European freshwater mussel, an aquatic bivalve mollusk in the family Margaritiferidae, the freshwater pearl mussels. Formerly found throughout western and central Europe, the species is now critically endangered, being confined to a few rivers in Spain and France. M. auricularia is commonly known as Spengler's freshwater mussel in honour of Lorenz Spengler, who first described this species.
Large shells are up to 180 mm in length.
It is found in:
The fish hosts for the glochidium larvae of this species are: Salaria fluviatilis, Gambusia holbrooki, Acipenser baerii, Acipenser naccarii and Acipenser sturio.
The hosts for this species were unknown for a long time: as recently as 1998 they were still not known.