Thick shelled river mussel
Encyclopedia
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.
, 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 larva
e.
due to deteriorating water quality.
Its native distribution is European.
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
of freshwater mussel, an aquatic
Aquatic animal
An aquatic animal is an animal, either vertebrate or invertebrate, which lives in water for most or all of its life. It may breathe air or extract its oxygen from that dissolved in water through specialised organs called gills, or directly through its skin. Natural environments and the animals that...
bivalve mollusk in the family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
Unionidae
Unionidae
Unionidae is a family of freshwater mussels, the largest in the order Unionoida, the bivalve mollusks sometimes known as river mussels, naiads, or simply as unionids.The range of distribution for this family is world-wide...
, the river mussels.
Ecology
As part of newly discovered reproductive behaviour, this mollusc crawls up to the edge of the water, exposing its excurrent apertureAperture (mollusc)
The aperture is an opening in certain kinds of mollusc shells: it is the main opening of the shell, where part of the body of the animal emerges for locomotion, feeding, etc....
, 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 larva
Larva
A larva is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle...
e.
Decline
The thick shelled river mussel declined in the beginning of the 20th century everywhere in EuropeEurope
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
due to deteriorating water quality.
Distribution
- It is mentioned in annexes II and IV of Habitats Directive.
Its native distribution is European.
- Croatia
- Czech Republic - in Bohemia, in Moravia, endangered (EN). It's Conservation status in 2004-2006 is bad (U2) in report for European commissionEuropean CommissionThe European Commission is the executive body of the European Union. The body is responsible for proposing legislation, implementing decisions, upholding the Union's treaties and the general day-to-day running of the Union....
in accordance with Habitats Directive. - Finland - in southern Finland. Vulnerable .
- France
- Germany - critically endangered (vom Aussterben bedroht) In Germany this bivalve has disappeared from 90% of its former range.
- Netherlands - locally extinct. In the NetherlandsNetherlandsThe Netherlands is a constituent country of the Kingdom of the Netherlands, located mainly in North-West Europe and with several islands in the Caribbean. Mainland Netherlands borders the North Sea to the north and west, Belgium to the south, and Germany to the east, and shares maritime borders...
it has not been seen alive after 1968 and is most likely extinctExtinctionIn biology and ecology, extinction is the end of an organism or of a group of organisms , normally a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and recover may have been lost before this point...
in that country. - Poland - endangered
- Slovakia - „nearly threatened“
- Sweden - „very rare“