''Sphaerium nucleus'' is a freshwater

bivalve Bivalvia (), in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class of marine and freshwater molluscs that have laterally compressed bodies enclosed by a shell consisting of two hinged parts. As a group, bival ...

of the

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

Sphaeriidae Sphaeriidae is a family of small to minute freshwater bivalve molluscs in the order Sphaeriida. In the US, they are commonly known as pea clams or fingernail clams. Heard, William H. 1977. Reproduction of fingernail clams (Sphaeriidae: ''Sphaeri ...

. It has been often confused with ''

Sphaerium corneum ''Sphaerium corneum'', also known as the European fingernailclam, is a very small freshwater clam, an aquatic bivalve mollusk in the family Sphaeriidae, the fingernail clams. Description The shell is fairly globular and can grow up to 9–13.5 ...

'' and is consequently quite poorly known.

Description

''Sphaerium nucleus'' is a very small bivalve which may grow up to 8mm in width and length. It differs from ''

'' 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 In biological classification, subspecies is a rank below species, used for populations that live in different areas and vary in size, shape, or other physical characteristics (morphology), but that can successfully interbreed. Not all species ...

of ''

''. 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.

Distribution

''S. nucleus'' occurs widely in Europe, from Spain to Ukraine. It appears to be absent from Russia. * Austria * Britain and Ireland (but see) *

Czech Republic The Czech Republic, or simply Czechia, is a landlocked country in Central Europe. Historically known as Bohemia, it is bordered by Austria to the south, Germany to the west, Poland to the northeast, and Slovakia to the southeast. The ...

– in Bohemia, in Moravia Horsák M., Juřičková L., Beran L., Čejka T. & Dvořák L. (2010). "Komentovaný seznam měkkýšů zjištěných ve volné přírodě České a Slovenské republiky. nnotated list of mollusc species recorded outdoors in the Czech and Slovak Republics. ''Malacologica Bohemoslovaca'', Suppl. 1: 1-37
PDF
* Germany * Kyrgyzstan (but see) * Slovakia * UkrainePripyat Marshes of Ukraine, RGS 1998 Ralph Brown Expedition: report by Dr O.V. Korniushin http://www.minter.demon.co.uk/brown/results/korniush.htm

Ecology

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

References

External links

''Sphaerium nucleus''
at

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''Sphaerium nucleus''
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nucleus Nucleus ( : nuclei) is a Latin word for the seed inside a fruit. It most often refers to: *Atomic nucleus, the very dense central region of an atom *Cell nucleus, a central organelle of a eukaryotic cell, containing most of the cell's DNA Nucle ...

Molluscs of Europe Freshwater bivalves Bivalves described in 1820 Taxobox binomials not recognized by IUCN