Anisus vorticulus

Anisus vorticulus (lesser ramshorn snail or little whirlpool ramshorn snail) is a species of minute, air-breathing, freshwater snail, an aquatic gastropod mollusk in the family Planorbidae, the ramshorn snails.

Anisus vorticulus
Shells of Anisus vorticulus

Data Deficient  (IUCN 3.1)[1]
Scientific classification
Kingdom:
Animalia
Phylum:
Mollusca
Class:
Gastropoda
(unranked):
clade Heterobranchia
clade Euthyneura
clade Panpulmonata
clade Hygrophila
Superfamily:
Planorboidea
Family:
Planorbidae
Subfamily:
Planorbinae
Tribe:
Planorbini
Genus:
Anisus
Subgenus:
Disculifer
Species:
A. vorticulus
Binomial name
Anisus vorticulus
(Troschel, 1834)[2]

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]

Distribution

Anisus vorticulus occurs in Czech Republic[4] - critically endangered (CR).[5] Its Conservation status in 2004–2006 is bad (U2) in report for European commission in accordance with Habitats Directive.[6] England - vulnerable (VU),[7] listed in List of endangered species in the British Isles. It is currently the focus of a Back from the Brink project.[8] Ireland, Germany - critically endangered (vom Aussterben bedroht),[9] Netherlands,[10] Poland, Slovakia,[4] Latvia and Croatia - in the Krka National Park. First finding of this species in Croatia was in 2009.[1]

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][11]

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 are lots of duckweed Lemna spp..[11] Water quality that is suitable for Anisus vorticulus is water without turbidity, with a high pH and a low level of nutrients.[1][11] The main threats to this snail include land drainage, poor habitat management and eutrophication.[11]

References
  1. Van Damme D. (2012). "Anisus vorticulus". The IUCN Red List of Threatened Species. Version 2014.3. <www.iucnredlist.org>. Downloaded on 22 February 2015.
  2. Troschel F. H. (1834). De limnaeaceis seu de gasteropodis pulmonatis quae nostris in aquis vivunt. pp. [1-5], 1-65, [1]. Berolini. page 51.
  3. Thorp, James H.; Rogers, D. Christopher (2018). Thorp and Covich's Freshwater Invertebrates: Volume 4: Keys to Palaearctic Fauna. Elsevier. p. 334. ISBN 978-0-12-385024-9.
  4. (in Czech) Horsák M., Juřičková L., Beran L., Čejka T. & Dvořák L. (2010). "Komentovaný seznam měkkýšů zjištěných ve volné přírodě České a Slovenské republiky. [Annotated list of mollusc species recorded outdoors in the Czech and Slovak Republics]". Malacologica Bohemoslovaca, Suppl. 1: 1-37. PDF.
  5. Juřičková L., Horsák M. & Beran L. (2001) "Check-list of the molluscs (Mollusca) of the Czech Republic". Acta Societatis Zoologicae Bohemicae 65: 25-40.
  6. (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 přírody 62(5): appendix 5:I-IV.
  7. UK Biodiversity Action Plan "Species Action Plan". Archived from the original on 2007-06-25. Retrieved 2007-03-05.
  8. "Little Whirlpool Ramshorn Snail". Back from the Brink. Retrieved 16 August 2018.
  9. (in German) Glöer P. & Meier-Brook C. (2003) Süsswassermollusken. DJN, pp. 134, page 109, ISBN 3-923376-02-2.
  10. "Anemoon > Flora en Fauna > Soorteninformatie". www.anemoon.org (in Dutch).
  11. "Lesser whirlpool ram's-horn snail: Anisus vorticulus". JNCC. Retrieved 15 March 2020.
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