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Anisus vorticulus

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Taxonomy [top]

Kingdom Phylum Class Order Family
ANIMALIA MOLLUSCA GASTROPODA HYGROPHILA PLANORBIDAE

Scientific Name: Anisus vorticulus
Species Authority: (Troschel, 1834)
Common Name/s:
English Lesser Ramshorn Snail, Little Whirlpool Ram's-horn Snail, Ram's-horn Snail
Synonym/s:
Anisus bavaricus Westerlund, 1885
Anisus bavaricus Westerlund, 1885
Anisus bavaricus Westerlund, 1885
Anisus bavaricus Westerlund, 1885
Anisus bavaricus Westerlund, 1885
Anisus (Disculifer) vorticulus Boettger, 1944
Anisus (Disculifer) vorticulus Boettger, 1944
Anisus (Disculifer) vorticulus Boettger, 1944
Anisus (Disculifer) vorticulus Boettger, 1944
Anisus (Disculifer) vorticulus Boettger, 1944
Planorbis charteus Held, 1837
Planorbis charteus Held, 1837
Planorbis charteus Held, 1837
Planorbis charteus Held, 1837
Planorbis charteus Held, 1837
Planorbis vorticulus Troschel, 1834
Planorbis vorticulus Troschel, 1834
Planorbis vorticulus Troschel, 1834
Planorbis vorticulus Troschel, 1834
Planorbis vorticulus Troschel, 1834
Spiralina vorticulus Ehrmann, 1933
Spiralina vorticulus Ehrmann, 1933
Spiralina vorticulus Ehrmann, 1933
Spiralina vorticulus Ehrmann, 1933
Spiralina vorticulus Ehrmann, 1933
Taxonomic Notes: It is possible to confuse specimens of Anisus vorticulus with dwarf forms of A. vortex that occur in temporary water bodies (described as Planorbis numulus Held 1837) (Terrier et al. 2006).

Assessment Information [top]

Red List Category & Criteria: Data Deficient ver 3.1
Year Published: 2012
Date Assessed: 2012-03-05
Assessor/s: Van Damme, D.
Reviewer/s: Bohm, M., Collen, B. & Seddon, M.
Contributor/s: Vavrova, L., Dyer, E., Soulsby, A.-M., Whitton, F., Kasthala, G., McGuinness, S., Milligan, HT, De Silva, R., Herdson, R., Thorley, J., McMillan, K., Collins, A., Offord, S., Duncan, C. & Richman, N.
Justification:
Anisus vorticulus has been assessed as Data Deficient as population declines have been observed throughout its global range. While the species has been listed as Near Threatened in the latest European assessment, there is a lack of population data and knowledge of threats across the eastern extent of its distribution (which was outside the scope of the European assessment) which is preventing this species from attaining a definitive risk category until additional research and data becomes available.

Geographic Range [top]

Range Description: This species occurs in central and eastern Europe to the Ob River in Russia, and north to the Skåne province in Sweden (Terrier et al. 2006). It is also reported to be found in northern Kazakhstan (Kantor et al. 2009) and Turkey (Sereflisan et al. 2009) with local populations occurring sporadically.
Countries:
Native:
Albania; Austria; Belarus; Belgium; Bulgaria; Czech Republic; Denmark; France (France (mainland)); Germany; Hungary; Italy (Italy (mainland)); Latvia; Lithuania; Macedonia, the former Yugoslav Republic of; Netherlands; Poland; Romania; Russian Federation (Kaliningrad); Slovakia; Sweden; Switzerland; Ukraine (Ukraine (main part)); United Kingdom (Great Britain, Northern Ireland)
Range Map: Click here to open the map viewer and explore range.

Population [top]

Population: This species is local throughout central and southern Europe (UKBAP 1995). In England, declines have occurred since 1965, with no colonies recorded outside East Anglia since the 1980s, and systematic sampling in formerly well-known sites failing to find any live specimens (UKBAP 1995, JNCC 2007). Some recolonization appears to have occurred as a result of improved water quality in Suffolk (UKBAP 1995, JNCC 2007). In 2008, its status was described as "Fluctuating - probably declining", with seven known populations still existing (UKBAP 2008), although this has improved from a status of "Declining (continuing/accelerating)" in 2005. In Germany, Glöer and Groh (2007) found abundances in excess of 300 individuals per m2 in some populations in Hamburg and Karlsruhe, although most were between 1-50 individuals per m2.
Population Trend: Decreasing

Habitat and Ecology [top]

Habitat and Ecology: This species inhabits unpolluted, calcareous waters in well-vegetated marsh drains (UKBAP 1995), as well as other low and clear water habitats such as floodplains, pools, streams, slow rivers and oxbow lakes. It is usually found in the littoral zone of lakes or on river banks. See Terrier et al. (2006) for a complete list of recorded habitats.

Glöer and Groh (2007) characterized this species as a "stenotopic r-strategist", meaning that it is a habitat specialist (can only live in sunlit habitats with clear water), but is ecologically robust with a rapid rate of population growth, breeding from March until July-November. In this way, it can quickly recover after habitat loss as long if there is suitable habitat remaining (Glöer and Groh 2007). This species can also survive freezing and dessication (Glöer and Groh 2007).
Systems: Freshwater

Threats [top]

Major Threat(s): Lilleleht (1998) lists threats to this species in Estonia as changes in waterbodies (channelization, dredging, water level regulation), environmental toxins, air pollution, and acidification.

In England, ditch clearance, nutrient enrichment (from fertiliser use), and changing land practices associated with lowering water tables are threatening this species (UKBAP 1995). Recent research also found that this species is highly vulnerable to the effects of habitat fragmentation which is likely to be a major threat throughout its range (Niggebrugge et al. 2007).

Glöer and Groh (2007) found that the availability of suitable, pristine habitat was the most important determinant of abundance in Germany. Thus, any kind of habitat degradation is likely to be a threat to this species. However, as Terrier et al. (2006) state, "the causes of the decline observed in [this species] are not well understood", and may be due to a range of disparate factors depending on geographic location.

Invasive water plants will also influence populations through shading, such as the American floating marshpennywort, Hydrocotyle ranunculouides, that chokes ditches in Belgium and the Netherlands and the Himalayan Balsam, Impatiens glandulifera that grows along ditches across Europe. Destruction of the typical habitat of the species also occurs over large parts of Europe due to explosive growth of  populations of (introduced) carp and geese (D.V. Damme pers. comm. 2011).

Conservation Actions [top]

Conservation Actions: This species is listed as Critically Endangered in the Czech Republic (Farkac et al. 2005), and in Sweden under criteria B1ab(iii)+2ab(iii): fragmented and declining distribution (Gärdenfors 2005).  In the UK, it was assessed (pre-1994) as Vulnerable and is a Priority Species on the UK Biodiversity Action Plan (BAP 2007; based on declines) and the English NERC Biodiversity List for restricted geographic range (JNCC 2010). In Estonia, it is listed as "rare" using non-IUCN criteria (Lilleleht 1998) and in Poland as Near Threatened (Glowacinski et al. 2002). It has also been listed as "endangered" in Germany, "strongly endangered" in Switzerland, "in danger of extinction" in Austria, and belongs to the "Red List candidates" in the Netherlands (Terrier et al. 2006). This species was recently added to Annexes II and IV of the EU Habitats Directive (Terrier et al. 2006, Niggebrugge et al. 2007), requiring special areas for conservation and strict protection.

This species has low dispersal ability and is vulnerable to the effects of habitat fragmentation (Niggebrugge et al. 2007). As such, creation of suitable reserve networks is important to halt declines where suitable habitat has been lost, e.g., in marshland drainage systems in England. Reintroduction to former areas may also be essential to the continuing viability of this species. Suitable areas of habitat should be managed by removing weeds and riparian vegetation shading the water; fenced to reduce the effects of livestock grazing; and fertilizers and toxic pollutants prevented from entering the water and causing eutrophication (see Glöer and Groh (2007) for examples in the Elbe, Germany; and Terrier et al. (2006) for an exhaustive list of management prescriptions).

Additional research into the population size and trends, ecology and threats of this species is recommended to aid the listing of this species in an adequate Red List category in the future.
Citation: Van Damme, D. 2012. Anisus vorticulus. In: IUCN 2013. IUCN Red List of Threatened Species. Version 2013.2. <www.iucnredlist.org>. Downloaded on 18 April 2014.
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