Swollen River Mussel Unio (Unio) tumidus

Class Bivalvia (Bivalves)
Order Unionoida
Family Unionidae (Freshwater mussels)
Species Unio (Unio) tumidus Retzius, 1788

Length of shell 62-130 mm.

This mussel has a thick shell with swollen umbos. It is green to chestnut brown, often with green rays. The hinge plate is is short and curved with prominent lateral teeth. Right anterior lateral and left cardinal teeth have serrated edges. Anterior adductor scar very close to shell margin.

Seen all year round mainly in large, calcareous lowland rivers and canals. Known from England and Wales, principally in the ‘canal basin’ of lowland, central England. Absent from Sotland and Ireland. Possibly declining.

Found in local canal, South Staffordshire July 2021. © Peter Hillman.

Species identification confirmed and recorded by an expert from iRecord.