Pisidium moitessierianum 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 minute freshwater clam. It is 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 mollusc in the family Sphaeriidae.

Description

This species is the smallest of the pea clams or Pisidium

Pisidium

Pisidium is a genus of very small or minute freshwater clams known as pill clams or pea clams, aquatic bivalve molluscs in the family Sphaeriidae.-Subgenera and species:Subgenera and species within the genus Pisidium include:...

species, and the smallest of any freshwater bivalve, at 2.5 mm adult size.

Distribution

The species is native to Europe, but has been introduced to northeastern North America.

• Czech Republic - in Bohemia, in Moravia, - endangered (EN)
• Germany - endangered (gefährdet)