Sphaerium nucleus

Sphaerium nucleus is a freshwater bivalve of the family Sphaeriidae. It has been often confused with Sphaerium corneum and is consequently quite poorly known.^[1]

Sphaerium nucleus
Conservation status
Least Concern  (IUCN 3.1)[1]
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Mollusca
Class:	Bivalvia
Order:	Sphaeriida
Family:	Sphaeriidae
Genus:	Sphaerium
Species:	S. nucleus
Binomial name
Sphaerium nucleus (Studer, 1820)[2]
Synonyms
Sphaerium corneum var. nucleus Cyclas nucleus Studer, 1820

Description

Sphaerium nucleus is a very small bivalve which may grow up to 8mm in width and length. It differs from Sphaerium corneum only in details. Like almost all bivalves, it is a filter-feeder.

Taxonomy

Sphaerium nucleus was described by Studer 1820, who placed it in the genus Cyclas. It was later thought to be a subspecies of Sphaerium corneum. Subsequently it was raised to a full species again as Sphaerium nucleus (Studer, 1820) due to its having a different form of kidney, and the shell having a broad hinge plate, dense porosity and more tumid shells with broad umbones. Unlike S. corneum it has a preference for temporary habitats.^[3]

Distribution

S. nucleus occurs widely in Europe, from Spain to Ukraine. It appears to be absent from Russia.^[1]

• Austria^[4]
• Britain and Ireland^[5][6] (but see^[1])
• Czech Republic – in Bohemia, in Moravia^[7][8]
• Germany^[9]
• Kyrgyzstan^[10] (but see^[1])
• Slovakia^[11]
• Ukraine^[12]

Ecology

This species lives in standing freshwater habitats, specifically in swampy conditions in drainage ditches and occasionally in lake margins, including temporary lakes.^[1]