The depressed river mussel or compressed river mussel, Pseudanodonta complanata, is a species

Species

In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

 of freshwater

Freshwater

Fresh water is naturally occurring water on the Earth's surface in ice sheets, ice caps, glaciers, bogs, ponds, lakes, rivers and streams, and underground as groundwater in aquifers and underground streams. Fresh water is generally characterized by having low concentrations of dissolved salts and...

 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...

, an 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 mollusk in the family Unionidae

Unionidae

Unionidae is a family of freshwater mussels, the largest in the order Unionoida, the bivalve mollusks sometimes known as river mussels, naiads, or simply as unionids.The range of distribution for this family is world-wide...

, the river mussels. The species name comes from the flattened shape of its shell.

This species is found throughout northern Europe, but it is endangered throughout its range.

While the survival of this species is thought to be threatened by pollution

Pollution

Pollution is the introduction of contaminants into a natural environment that causes instability, disorder, harm or discomfort to the ecosystem i.e. physical systems or living organisms. Pollution can take the form of chemical substances or energy, such as noise, heat or light...

 and the dredging of the slow-moving channels of water in which it lives, the species is also said to be "easily overlooked" (it can be confused with Anodonta anatina or juvenile Anodonta cygnea) and thus it may be actually be more prevalent than current records show.

Distribution

Its native distribution is European. It has been recorded from:

• Czech Republic - in Bohemia, in Moravia, endangered (EN). It is endangered in Bohemia and critically endangered in Moravia.
• Estonia - present.
• Finland - not uncommon.
• Germany
  • critically endangered (vom Austerben bedroht)
  • Listed as strictly protected species and as specially protected species in annex 1 in Bundesartenschutzverordnung.
• Netherlands - present
• Poland - endangered

• Slovakia - endangered
• United Kingdom - see Action plan for Pseudanodonta complanata, (British Isles - listed in List of endangered species in the British Isles)
• Sweden - rare