Pisidium moitessierianum

Pisidium moitessierianum is a species of small freshwater clam. It is an aquatic bivalve mollusc in the family Sphaeriidae.

Pisidium moitessierianum
Scientific classification
Kingdom:	Animalia
Phylum:	Mollusca
Class:	Bivalvia
Order:	Sphaeriida
Family:	Sphaeriidae
Genus:	Pisidium
Species:	P. moitessierianum
Binomial name
Pisidium moitessierianum Paladilhe, 1866

Description

This species is the smallest of the pea clams or Pisidium species, and the smallest of any freshwater bivalve, at 1.5 – 2.5 mm adult size. The shell is long-oval and oblique wedge-shaped with prominent umbos which are slightly behind the midpoint. The umbos are demarcated by a shallow furrow. The surface (periostracum) is silky, with regular concentric striae.

Drawing of the right valve external view of Pisidium moitessierianum.

Drawing of the right valve lateral view of Pisidium moitessierianum.

Drawing of the right valve internal view of Pisidium moitessierianum.

Distribution

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

• Czech Republic – in Bohemia, in Moravia,^[1] - endangered (EN)^[2]
• Slovakia^[1]
• Germany – endangered (gefährdet)^[3]
• Nordic countries: Denmark, Finland, Norway and Sweden (not in Faroes, Iceland)^[4]
• Great Britain and Ireland^[5]