The Dreissenidae are a family of small freshwater mussel

Mussel

The common name mussel is used for members of several families of clams or bivalvia mollusca, from saltwater and freshwater habitats. These groups have in common a shell whose outline is elongated and asymmetrical compared with other edible clams, which are often more or less rounded or oval.The...

s, aquatic

Aquatic animal

An aquatic animal is an animal, either vertebrate or invertebrate, which lives in water for most or all of its life. It may breathe air or extract its oxygen from that dissolved in water through specialised organs called gills, or directly through its skin. Natural environments and the animals that...

 bivalve mollusks. They attach themselves to stones or to any other hard surface using a byssus

Byssus

Byssus means both a silky filament by which certain molluscs attach themselves to hard surfaces, and a rare fabric, also called sea silk and its fibre source.-Word:...

.

Genera

Genera within the family Dreissenidae include:

• Congeria
• Dreissena
  Dreissena
  Dreissena is a genus of small freshwater mussels in the family Dreissenidae.-Species:* Dreissena polymorpha, the zebra mussel** Dreissena polymorpha polymorpha** Dreissena polymorpha andrusovi* Dreissena bugensis, the quagga mussel...
  
  , the type genus
  Type genus
  In biological classification, a type genus is a representative genus, as with regard to a biological family. The term and concept is used much more often and much more formally in zoology than it is in botany, and the definition is dependent on the nomenclatural Code that applies:* In zoological...
  
   of the family
• Mytilopsis
  Mytilopsis
  Mytilopsis is a genus of small freshwater false mussels in the family Dreissenidae.-Species:Species within the genus Mytilopsis include:* Mytilopsis domininguensis* Mytilopsis leucophaeata* Mytilopsis sallei-References:...
  
  

Shell morphology

The shells of species of mussels in this family range from 20–40 mm in their maximum dimension, and about half as wide across. 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.

Biology and ecology

These mussels breathe via complex gills. 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.

Geographical range of distribution

In Britain there is only one species from this family, Dreissena polymorpha, the zebra mussel, which is a troublesome invasive species

Invasive species

"Invasive species", or invasive exotics, is a nomenclature term and categorization phrase used for flora and fauna, and for specific restoration-preservation processes in native habitats, with several definitions....

. In the USA, both D. polymorpha and D. bugensis are problematic introduced species.