The shells of these mussels are variable in shape, but usually equivalve and elongate. They have solid, nacreous valves … See more

Although some fossil freshwater bivalves from the Carboniferous and Permian periods have been suggested to be unionids, other authors have suggested that they are likely to be unrelated, due to lacking the internal nacreous layer … See more

Families, genera, and species in the order Unionida are found on six continents, where they are restricted exclusively to freshwater rivers, streams, creeks and some lakes. There are approximately 900 species wo… See more

Unionida burrow into the substrate in clean, fast flowing freshwater rivers, streams and creeks, with their posterior margins exposed. They pump water through the incurrent aperture, obtaining oxygen and filtering foo… See more

Unionida have a unique and complex life cycle involving parasitic larvae. This larval form used to be described as "parasitic worms" on the fish host, however, the larvae are not "worms" and do not harm fish under … See more

Many of these freshwater mussel species face conservation issues due to habitat degradation and in some cases due to over-exploitation for the freshwater pearl industry, and for the nacre of their shells, which was used in … See more