Anisus vorticulus (lesser ramshorn snail or little whirlpool ramshorn snail) is a species of small, air-breathing, freshwater snail, an aquaticgastropodmollusk in the family Planorbidae, the ramshorn snails.
Description
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]
In the British Isles, this species is restricted to a small number of sites in the Norfolk Broads and the Pevensey Levels and Arun Valley in Sussex and Surrey.[1][13]
Habitat
This small snail lives in pools with standing water and in oxbow lakes, but these biotopes are threatened because of sedimentation and ecological succession. It favours ditches with much aquatic flora but little emergent vegetation. Invasive plants such as floating marsh pennywort, (Hydrocotyle ranunculouides), that sometimes chokes ditches, and the Himalayan balsam (Impatiens glandulifera) are particularly harmful.[1]
This species often lives in places where there is abundant duckweed Lemna spp.[13]Water quality that is suitable for Anisus vorticulus is water without turbidity, with a high pH and a low level of nutrients.[1][13] The main threats to this snail include land drainage, poor habitat management and eutrophication.[13]
References
^ abcdeVan Damme D. (2012). "Anisus vorticulus". The IUCN Red List of Threatened Species. Version 2014.3. >www.iucnredlist.org<. Downloaded on 22 February 2015.
^Troschel F. H. (1834). De limnaeaceis seu de gasteropodis pulmonatis quae nostris in aquis vivunt. pp. [1-5], 1-65, [1]. Berolini. page 51.
^Juřičková L., Horsák M. & Beran L. (2001) "Check-list of the molluscs (Mollusca) of the Czech Republic". Acta Societatis Zoologicae Bohemicae65: 25-40.
^(in Czech) 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 přírody62(5): appendix 5:I-IV.
