page_title: Theodoxus fluviatilis
section_title: Europe
hierarchical_section_title: Theodoxus fluviatilis / Distribution / Europe
caption_attribution_description: English: New Vorontsov lighthouse in Odessa, Ukraine
context_page_description: Theodoxus fluviatilis, common name the river nerite, is a species of small freshwater and brackish water snail with a gill and an operculum, an aquatic gastropod mollusk in the family Neritidae, the nerites.
  This widely distributed neritid snail species occurs from Europe to Central Asia. It has a thick shell with a calcified operculum. The coloration pattern on the shell is very variable. Theodoxus fluviatilis lives in freshwater and in brackish water, in rivers and lakes on stones. It feeds mainly by grazing on biofilms and diatoms.
  Some of the populations of this species are spreading, and these can reach densities up to thousands of snails per square meter. Females lay egg capsules, each of which contains a large number of eggs, but only one snail hatches from the capsule. The snails reach sexual maturity in a year, and the total lifespan is 2 or 3 years.
context_section_description: The species occurs widely in Western Europe, and it is also widespread in the north of Ireland, living in 10% of Irish streams and rivers.
  It lives in Great Britain, including the Orkney Islands, as well as in the Netherlands, Belgium, Luxembourg, Liechtenstein, and Monaco. It also is found in France and Switzerland, where it is considered to be critically endangered. More to the south, it occurs in Spain and Portugal, although the species is restricted to karst springs in Central Portugal.
  In central Europe, this species has been recently introduced in the Austrian Danube, where it was first recorded in Tulln, Lower Austria in 2001. In the Czech Republic, it is now extinct in Bohemia; the only findings were in the Elbe river near Litoměřice in 1917, and the most recent findings of empty shells took place in 1943. Theodoxus fluviatilis also occurs in Poland, in Slovakia where it is non-indigenous since 2002, and in Hungary. Zettler (2008) provided a detailed bibliography of the distribution of T. fluviatilis in Germany. The indigenous distribution of T. fluviatilis included all of the large rivers: Rhine, Main, Moselle, Neckar, Weser, Elbe and Oder. However, this species is now highly endangered in Germany (Stark gefährdet).
  In Northern Europe, this species is found in Denmark, in Sweden as far north as 58° N. It can also be found on the coasts of Finland, in the Åland Islands, and is known to be found alive there since 1994. No other Theodoxus species reaches the Baltic Sea. It has the northernmost distribution of the genus Theodoxus and it is also the northernmost species of all Neritidae. In Eastern Europe this snail occurs in Estonia, Lithuania, and Latvia, as well as Belarus, and in Russia from western Russia to Caucasus. Since 1997 it has been found in the Gulf of Odessa, Ukraine. In Ukraine and in Crimea it is non-indigenous, and was first recorded in the area in 1955. It also occurs in Moldova. In Southern Europe, Theodoxus fluviatilis  lives in Albania, Bosnia and Herzegovina, Romania, Bulgaria, Slovenia, and Croatia. In Macedonia and Albania it occurs in Lake Ohrid (which spans the border of the two countries) as the subspecies Theodoxus fluviatilis dalmaticus. It is found on the mainland of Greece and also on Crete.
  It is known to occur in the mainland of Italy and also in Sardinia. It occurs in Montenegro, and in Serbia.
caption: The Gulf of Odessa is one of the locations where Theodoxus fluviatilis is known to occur.
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