Dreissena Mytilopsis Congeria Rheodreissena The Dreissenidae are a family of small freshwater aquatic bivalve molluscs, commonly called mussels although not at all closely related to true mussels.

The shells of these bivalves are shaped somewhat like those of true mussels, which they also resemble in attaching themselves to a hard substrate such as stone using a byssus; however, this group is more closely related to the venus clams (Veneridae).

The shell outline is bent, with one margin usually somewhat incurved, and the other strongly curved outwardly.

The shell is opaque and robust; in coloration it is yellowish, brownish or greyish, often with light-and-dark stripes.

They live in clean, well oxygenated, lowland rivers, canals and reservoirs, attaching to stones and other hard surfaces; they will also tolerate slightly brackish water.