Thick shelled river mussel

Taxobox
name = Thick shelled river mussel


image_caption =
status = LR/nt
trend =
status_system = iucn2.3
regnum = Animalia
phylum = Mollusca
classis = Bivalvia
ordo = Unionoida
familia = Unionidae
genus = "Unio"
species = "U. crassus"
binomial = "Unio crassus"
binomial_authority = Philipsson, 1788

The thick shelled river mussel, "Unio crassus", is a mussel of the family Unionidae.

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 in the beginning of the 20th century everywhere in Europe due to deteriorating water quality.

Distribution and conservation status

* IUCN Red List - Near threatened (NT) [Mollusc Specialist Group 1996. Unio crassus. In: IUCN 2006. 2006 IUCN Red List of Threatened Species. . Cited February 10 2007. http://www.iucnredlist.org/search/details.php/22736/summ mentioned as: LR/nt ver 2.3 (1994)]
* It is mentioned in annexes II and IV of Habitats Directive.

Its native distribution is European.

* The Czech Republic - endangered (EN). [Juřičková L., Horsák M. & Beran L., 2001: Check-list of the molluscs (Mollusca) of the Czech Republic. Acta Soc. Zool. Bohem., 65: 25-40.] [Red List of the molluscs (Mollusca) of the Czech Republic http://mollusca.sav.sk/malacology/redlist.htm] It's Conservation status in 2004-2006 is bad (U2) in report for European commission in accordance with Habitats Directive. [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)]
* France [cite web|url=http://natura2000.environnement.gouv.fr/especes/1032.html |title=Recherche de sites par espèce: Invertébrés: Unio crassus (Unio crassus) |year=2007]
* Germany - critically endangered ("vom Aussterben bedroht") [Glöer P. & Meier-Brook C. (2003) Süsswassermollusken. DJN, pp. 134, strana 109, ISBN 3-923376-02-2] 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. [MinLNV>Dutch Ministry of Agriculture, Nature and Food Quality - Nature Law - Bataafse stroommossel ("Unio crassus"). Accessed at [http://www.synbiosys.alterra.nl/natura2000/hoofdpagina.aspx?subj=soorten&groep=1&id=32 the ministries website] ] [http://www.anemoon.org/anm/voorlopige-kaarten/zoetwatermollusken/wetenschappelijk/unio-crassus/]
* Poland - endangered [Polish Red Data Book of Animals http://www.iop.krakow.pl/pckz/opis.asp?id=130&je=en]
* Slovakia - „nearly threatened“ [cs icon [http://www.mollusca.cz/table/table.php Měkkýši (Mollusca) České republiky a Slovenska ] ]
* Sweden - „very rare“ [ [http://www.nrm.se/researchandcollections/zoology/invertebratezoology/factsoninvertebrates/thelargefreshwatermussels/thickshelledrivermussel.4.5fdc727f10d795b1c6e800012441.html Thick shelled river mussel - Naturhistoriska riksmuseet ] ]

References

External links

* [http://clade.acnatsci.org/mussel/m/mom/archive/2005/05-11.html The Mussel Project Web Site]