The zebra mussel, Dreissena polymorpha, is a small freshwater mussel. This species was originally native to the lakes of southeast Russia[1] being first described in 1769 by a German zoologist Peter Simon Pallas in the Ural, Volga and Dnieper rivers. They are still found nearby, as Pontic (Black Sea) and Caspian (Caspian Sea) species.[2] However, it has been accidentally introduced in many other areas, and has become an invasive species in many different countries worldwide.
Zebra mussels superficially resemble marine mussels in the family Mytilidae, and like them, are attached to solid substrates with a byssus. However, zebra mussels are not at all closely related to the mytilids; they are much more closely related to the Veneridae, the Venus clams.
Zebra mussels get their name from a striped pattern which is commonly seen on their shells, though not all shells bear this pattern. They are usually about the size of a fingernail, but can grow to a maximum length of nearly 2 in (5.1 cm).[3] The shape of the shell is also somewhat variable.
