3 Molluscs
3 Molluscs 3 Molluscs
3 Molluscs Anisus vorticulus Little Ramshorn Whirlpool Snail Anisus vorticulus Troschel, 1834 Little ramshorn whirlpool snail (Anisus vorticulus) M. Horsák Little Ramshorn Whirlpool Snail Latin synonyms: Planorbis vorticulus Troschel, 1834. Taxonomic classification: Order: Hygrophila Family: Planorbidae Status: CR – Critically Endangered Morphology The shell is very flat, discoid, thinwalled with almost flat disc and slightly concave under side. The colour reminds of brownish to reddish horn. The shell has 5–51/2 convex whorls, (whorls of the base side are shorter), the last one being only 1,5 times wider than the penultimate one. The keel is simple, relatively blunt, mostly situated slightly below the centre of whorls and can have a membraneous edge. The shell peristome is simple, sharp, its lower segment joins the last whorl under the keel. The shell height is 0,80– 0,85mm, the width is 5–6mm. Bionomics Little ramshorn whirlpool snail occurrence is bound to stagnant waters overgrown by vegetation in floodplains of large rivers (the Danube, the Morava). According to observations in Pomoravie region, it occurs mostly in oxbows, flooded during high water level of the river (plesiopotamal). It occurs exceptionally also in fishponds (Senné) or thickly overgrown tiny borrow pits. The species has probably an increased demand for calcium content in water. It lives on algae growths and decayed parts of plants. Little ramshorn whirlpool snail is a hermaphrodite. 1
3 Molluscs Anisus vorticulus Little Ramshorn Whirlpool Snail Distribution A European species (Northern Italy, the Netherlands, Southern England, Denmark, Southern Sweden, Germany, the Czech Republic, Switzerland, Poland, Hungary, Russia). In the east its area of distribution reaches to western Siberia. Distribution in Slovakia In the territory of Slovakia it has a relict occurrence. There are isolated localities especially in southern Slovakia (Podunajská rovina Plain, the Borská nížina Lowland) and eastern Slovakia (the Východoslovenská rovina Plain). The species occurs in 4 SACs. Threats It is especially degradation even liquidation of suitable sites, due to water flow regulations and building of water dams. The increasing eutrophication of several water flows, changes in species composition of water communities (competition of expansive or invasive species). An important factor is also the use of biocides in the vicinity of the species habitats. Densely vegetated river arm periodically flooded at high water levels are typical habitat of the little ramshorn whirpool snail. (Shrek side arm near Stupava town). T. Čejka 2
- Page 1 and 2: Atlas Atlas druhov európskeho výz
- Page 3 and 4: Autor Tomáš Čejka 3 Mäkkýše A
- Page 5 and 6: 3 Mäkkýše Anisus vorticulus Kot
- Page 7 and 8: 3 Mäkkýše Bythinella pannonica B
- Page 9 and 10: 3 Mäkkýše Theodoxus transversali
- Page 11 and 12: 3 Mäkkýše Unio crassus Korýtko
- Page 13 and 14: 3 Mäkkýše Vertigo angustior Pimp
- Page 15 and 16: 3 Mäkkýše Vertigo geyeri Pimprl
- Page 17 and 18: 3 Mäkkýše Vertigo moulinsiana Pi
- Page 19: Author Tomáš Čejka 3 Molluscs An
- Page 23 and 24: 3 Molluscs Bythinella pannonica Pan
- Page 25 and 26: 3 Molluscs Theodoxus transversalis
- Page 27 and 28: 3 Molluscs Unio crassus Thick-shell
- Page 29 and 30: 3 Molluscs Vertigo angustior Narrow
- Page 31 and 32: 3 Molluscs Vertigo geyeri Geyer’s
- Page 33: 3 Molluscs Vertigo moulinsiana Desm
3 <strong>Molluscs</strong><br />
Anisus vorticulus<br />
Little Ramshorn Whirlpool Snail<br />
Distribution A European species (Northern Italy, the<br />
Netherlands, Southern England, Denmark, Southern<br />
Sweden, Germany, the Czech Republic, Switzerland,<br />
Poland, Hungary, Russia). In the east its area of distribution<br />
reaches to western Siberia.<br />
Distribution in Slovakia In the territory of Slovakia it<br />
has a relict occurrence. There are isolated localities especially<br />
in southern Slovakia (Podunajská rovina Plain,<br />
the Borská nížina Lowland) and eastern Slovakia (the<br />
Východoslovenská rovina Plain).<br />
The species occurs in 4 SACs.<br />
Threats It is especially degradation even liquidation<br />
of suitable sites, due to water flow regulations and<br />
building of water dams. The increasing eutrophication<br />
of several water flows, changes in species composition<br />
of water communities (competition of expansive or<br />
invasive species). An important factor is also the use of<br />
biocides in the vicinity of the species habitats.<br />
Densely vegetated river arm periodically flooded at high water levels are typical habitat of the little ramshorn whirpool snail. (Shrek<br />
side arm near Stupava town). T. Čejka<br />
2
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