Sphaerium nucleus is a freshwater bivalve of the family Sphaeriidae. It has been often confused with Sphaerium corneum 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 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.Korniushin, A.V. 2001: Taxonomic revision of the genus Sphaerium s. l. in the Palaearctic region, with some notes on the North American species. Arch. Molluskenk. 129: 77–122.
Distribution S. nucleus occurs widely in Europe, from Spain to Ukraine. It appears to be absent from Russia.
Austriahttp://ipp.boku.ac.at/private/wf/Check_List_of_Austrian_Mollusca.html etzte Änderung am 24.10.2005. Cited March 24, 2007 Britain and IrelandAnderson, R. 2005, An Annotated List of the Non-Marine Mollusca of Britain and Ireland, Journal of Conchology, London, 38: 607–638.Killeen, I.J., Aldridge, D.C. & Oliver, P.G., 2004. Freshwater bivalves of Britain and Ireland. Field Studies Occasional Publication 82. FSC Publications, Shrewsbury. 114pp. (but see) Czech Republic – 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. [Annotated list of mollusc species recorded outdoors in the Czech and Slovak Republics]". Malacologica Bohemoslovaca, Suppl. 1: 1–37. PDF.Kořínková T., 2006: The first reliable records of Sphaerium nucleus (Mollusca: Bivalvia: Sphaeriidae) in the Czech Republic. Acta Soc. Zool. Bohem. 69: 293-297. ISSN 1211-376X pdf GermanyGlöer P. & Meier-Brook C., 2003: Süsswassermollusken. DJN, pp. 134, page 109, KyrgyzstanAnimalBase :: Sphaerium nucleus species homepage (but see) SlovakiaKošel V., 2006: The first record of Sphaerium nucleus (Bivalvia) in Slovakia. Biologia. Vol. 61, No. 5, page 524 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 Animalbase taxonomy, short description, distribution, biology, status (threats), images Sphaerium nucleus images at Encyclopedia of Life