Thick shelled river mussel

Thick shelled river mussel
Unio crassus from Lužnice River, Czech Republic
Conservation status
Endangered  (IUCN 3.1)[1]
Scientific classification
Kingdom:	Animalia
Phylum:	Mollusca
Class:	Bivalvia
Order:	Unionoida
Family:	Unionidae
Genus:	Unio
Species:	U. crassus
Binomial name
Unio crassus Philipsson, 1788

The thick shelled river mussel, scientific name Unio crassus, is a species of freshwater mussel, an aquatic bivalve mollusk in the family Unionidae, the river mussels.

Ecology

As part of newly discovered reproductive behaviour, this mollusc crawls up to the edge of the water, exposing its excurrent aperture, and then lets loose a stream of water. The fountain of water often contains glochidia, and it is suggested that this spurting behavior may facilitate dispersal of mussel larvae.

Decline

The thick shelled river mussel declined during the 20th century everywhere in Europe due to deteriorating water quality,^[2] habitat fragmentation and host fish limitation.^[3]

Distribution

• It is mentioned in annexes II and IV of Habitats Directive.

Its native distribution is European.

• Croatia
• Czech Republic - in Bohemia, in Moravia,^[4] endangered (EN).^[5][6] Its Conservation status in 2004-2006 is bad (U2) in report for European commission in accordance with Habitats Directive.^[7]
• Finland - in southern Finland. Vulnerable.^[8]
• France ^[9]
• Germany - critically endangered (vom Aussterben bedroht) ^[10] In Germany this bivalve has disappeared from 90% of its former range.
• Netherlands - locally extinct. In the Netherlands it has not been seen alive after 1968 and is most likely extinct in that country.^[11][12]
• Poland - endangered ^[13]
• Slovakia - „nearly threatened“ ^[14]
• Sweden - „very rare“ ^[15]
• Denmark - very rare ^[16]

References

1. Van Damme, D. (2011). "Unio crassus". IUCN Red List of Threatened Species. Version 2012.2. International Union for Conservation of Nature. Retrieved 22 April 2013.
2. Douda, K. 2010. Effects of nitrate nitrogen pollution on Central European unionid bivalves revealed by distributional data and acute toxicity testing. Aquatic Conservation: Marine and Freshwater Ecosystems 20 (2010): 189-197..
3. Douda, K., Horký, P., Bílý, M. (2012) Host limitation of the thick-shelled river mussel: identifying the threats to declining affiliate species. Animal Conservation, 15, 536-544. .
4. (Czech) 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.
5. Juřičková L., Horsák M. & Beran L., 2001: Check-list of the molluscs (Mollusca) of the Czech Republic. Acta Soc. Zool. Bohem., 65: 25-40.
6. Red List of the molluscs (Mollusca) of the Czech Republic http://mollusca.sav.sk/malacology/redlist.htm
7. Dušek J., Hošek M. & Kolářová J. (2007) Hodnotící zpráva o stavu z hlediska ochrany evropsky významných druhů a typů přírodních stanovišť v České republice za rok 2004-2006. - Ochrana přírody, 62(5): appendix 5:I-IV. (in Czech language)
8. "Threatened and Near Threatened molluscs". 2001.
9. "Recherche de sites par espèce: Invertébrés: Unio crassus (Unio crassus)". 2007.
10. Glöer P. & Meier-Brook C. (2003) Süsswassermollusken. DJN, pp. 134, strana 109, ISBN 3-923376-02-2
11. MinLNV>Dutch Ministry of Agriculture, Nature and Food Quality - Nature Law - Bataafse stroommossel (Unio crassus). Accessed at the ministries website
12. http://www.anemoon.org/anm/voorlopige-kaarten/zoetwatermollusken/wetenschappelijk/unio-crassus/
13. Polish Red Data Book of Animals http://www.iop.krakow.pl/pckz/opis.asp?id=130&je=en
14. (Czech) Měkkýši (Mollusca) České republiky a Slovenska
15. Thick shelled river mussel - Naturhistoriska riksmuseet
16. http://www.habitatarter.dk/arter.asp?id=3169

External links

• The Mussel Project Web Site
• Fauna Europea