| Anisus vorticulus | |
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| Shells ofAnisus vorticulus | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Mollusca |
| Class: | Gastropoda |
| Superorder: | Hygrophila |
| Family: | Planorbidae |
| Genus: | Anisus |
| Species: | A. vorticulus |
| Binomial name | |
| Anisus vorticulus | |
Anisus vorticulus (lesser ramshorn snail orlittle whirlpool ramshorn snail) is a species of small, air-breathing,freshwater snail, anaquaticgastropodmollusk in the family Planorbidae, the ramshorn snails.
The lesser ramshorn snail is a very small species growing to a maximum diameter of 5 mm (0.2 in). The shell lacks a keel and the peripheral angle is relatively prominent, with a slender, narrow periostracal fringe.[3]
Anisus vorticulus occurs inCzech Republic[4] - critically endangered (CR).[5] Its Conservation status in 2004–2006 is bad (U2) in report forEuropean Commission in accordance with Habitats Directive.[6]England - vulnerable (VU),[7] listed inList of endangered species in the British Isles. It is currently the focus of aBack from the Brink project.[8]Ireland,Germany - critically endangered (vom Aussterben bedroht),[9]Netherlands,[10]Poland,Slovakia - critically endangered,[4][11]Latvia andCroatia - in theKrka National Park. First finding of this species in Croatia was in 2009.[1][12]
In the British Isles, this species is restricted to a small number of sites in the Norfolk Broads and thePevensey Levels andArun Valley in Sussex and Surrey.[1][13]
This small snail lives in pools with standing water and inoxbow lakes, but these biotopes are threatened because ofsedimentation andecological succession. It favours ditches with much aquatic flora but little emergent vegetation. Invasive plants such as floatingmarsh pennywort, (Hydrocotyle ranunculouides), that sometimes chokes ditches, and theHimalayan balsam (Impatiens glandulifera) are particularly harmful.[1]
This species often lives in places where there is abundant duckweedLemna spp.[13]Water quality that is suitable forAnisus vorticulus is water withoutturbidity, with a high pH and a low level of nutrients.[1][13] The main threats to this snail include land drainage, poor habitat management andeutrophication.[13]
Anisus vorticulus is a protected species in the United Kingdom under the Conservation of Habitats and Species Regulations 2010 and a license is needed to possess live or dead specimens taken from the wild since October 2008.[14] The species has gained coverage in the UK as infrastructure projects impacting its habitats have been delayed. 800 snails living in ditches alongside theAcle Straight, a part of theA47 road, were moved to a new habitat in 2016, delaying expansion plans for the road until monitoring at the new habitats was complete in 2023.[15] In 2022, it was reported that the translocation had had "mixed" results;[16] in 2025,National Highways' full report found that it had been successful.[17][18]
Later in 2025, British ChancellorRachel Reeves was recorded saying she had unblocked a planned development of 20,000 homes at a site in Sussex which had "some snails on the site that are a protected species or something", apparently referring toA. vorticulus.[19] Craig Bennett, CEO ofThe Wildlife Trusts, said it was "shocking ... to hear the way that the chancellor just dismisses ecological science" and noted that there was a "proud tradition" of assessing the environmental impact of building projects before permitting them.[19]
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