Anodonta cygnea 

Scope: Europe
Language: English

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Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Mollusca Bivalvia Unionoida Unionidae

Scientific Name: Anodonta cygnea (Linnaeus, 1758)
Regional Assessments:
Common Name(s):
English Swan Mussel
Taxonomic Notes: Fauna Europaea (Bank et al. 2006) considered there to be four different subspecies, which, once reviewed using molecular systematics may be revealed as concealing cryptic diversity.
In addition Falkner (pers. comm., 2009) considered that two subspecies may exist in Lake Constance, although whether it is an endemic sub-species of Lake Constance is or whether they are conspecific with forms from other Swiss Alpine lakes is unclear.

Assessment Information [top]

Red List Category & Criteria: Near Threatened (Regional assessment) ver 3.1
Year Published: 2011
Date Assessed: 2010-02-02
Assessor(s): Killeen, I. & Aldridge, D.
Reviewer(s): von Proschwitz, T., Seddon, M.B., Van Damme, D. & Ward, J.
This species is a widespread species in Europe and is not considered threatened at present, although it is recognised as a species which is declining over parts of the range, in part due to the presence of the invasive species Dreissena polymorpha. The species is more in decline in Ireland and parts of western Europe (Moorkens and Killeen 2005). There is an urgent need for more data on the level of impact of Dreissena polymorpha, as it can stop Anodonta anatina from reproducing (Moorkens and Killeen 2005). It has reduced greatly in numbers in some major river systems in the range and, although there are many identified threats, the precise causes are unknown (D. Aldridge pers. comm. 2009).

Given the decline in populations over the last generation as a result of water pollution and the impact of the various invasive bivalves the species is a candidate for Near Threatened (NT) status in Europe, as it may have declined between 25 and 35% in a significant percentage of the range. Once sufficient data has been assembled to confirm the decline levels the threat status can be reassessed.

Geographic Range [top]

Range Description:This species is common and widespread throughout Europe, but scarcer in some parts. Fauna Europaea (Bank et al. 2006) considered there to be four different subspecies, which may once reviewed using molecular systematics be revealed as concealing cryptic diversity, and hence these are listed for information.

Anodonta cygnea cygnea
 (Linnaeus, 1758): Mainly northern European: Norway, Sweden, Denmark, Finland, Estonia, Latvia, Lithuania, Kalingrad region (Russia), Poland, Republic of Ireland, Great Britain (UK), Northern Ireland (UK), Netherlands, Belgium, Luxembourg, France (Mainland) and Germany.

Anodonta cygnea deplanata
von Gallenstein, 1852: Austria.

Anodonta cygnea gravida
Drouet, 1879:  Mainland Greece. 

Anodonta cygnea solearis
Held, 1839: Eastern European: Germany, Switzerland, Austria, Czech Republic, Slovakia, Hungary and Greece (including Andikíthira I., Evvia I., Ionian Is., Samothráki I., Northern Sporades Is., Thásos I.).

Outside Europe this species is found as far east as Siberia.

Countries occurrence:
Albania; Austria; Belgium; Croatia; Czech Republic; Denmark; Estonia; Finland; France (France (mainland)); Germany; Greece (Greece (mainland)); Hungary; Ireland; Italy (Italy (mainland)); Latvia; Lithuania; Luxembourg; Netherlands; Norway; Poland; Portugal (Portugal (mainland)); Romania; Russian Federation (Northwest European Russia, South European Russia); Serbia (Serbia); Slovakia; Spain (Spain (mainland)); Sweden; Switzerland; Turkey (Turkey-in-Europe); Ukraine; United Kingdom (Great Britain, Northern Ireland)
Additional data:
Range Map:156066-1

Population [top]

Population:The species is known to be declining through parts of the range in western Europe. In parts of Germany considered rare (Falkner pers. comm. 2009), where it is considered to be present in lakes.
Current Population Trend:Decreasing
Additional data:
Population severely fragmented:No

Habitat and Ecology [top]

Habitat and Ecology:This species prefers slow flowing or still waters, lakes and slow-flowing lowland rivers, canals, drainage dykes and dam reservoirs (Kerney 1999, Killeen et al. 2004, Zettler et al. 2006). It is intolerant of poor environmental conditions, and can be used as a biodiversity indicator of clean water (Rosińska et al. 2008).

Use and Trade [top]

Use and Trade: This species is known to be used for sale for large garden ponds and aquariums.

Threats [top]

Major Threat(s): In the past there have been localised declines and losses as the result of habitat degradation (water pollution from industrial/agricultural sources and channel management for flood protection and navigation), however the most recent threats come from the impact of an invasive mollusc species Dreissena polymorpha, smothering the swan mussel. In some parts of Europe this species has been badly impacted by Dreissena polymorpha and is projected to decline even further as a direct result of this invasive species (e.g. in Ireland, Moorkens and Killeen (2005)). The species sits partly out of the river bed to enable the filter-feeding, so a high proportion of shell is exposed to the water column, and hence is vulnerable to settlement by Dreissena polymorpha seeking a place to anchor. There is an urgent need for more data on the level of impact of this species as the smothering is known to inhibit reproduction.

Conservation Actions [top]

Conservation Actions: No conservation actions are known for this species operating across the range, although local actions are in place. In Poland, this species has been protected by law since 1995 and is listed as Endangered on the Polish Red List (Zając 2005). This species has special status in Germany by the BArtSchV (Anlage I) legislation (Federal Species Regulation) (Zettler et al. 2006), and where it is considered to be present in lakes and listed with a status of 2 - 'highly endangered' (Falkner pers. comm, 2009). It is also listed on the local Red List of endangered animals of Brandenburg and of Mecklenburg-Przedpomorza in Germany with a status of 3 - 'threatened' (Rosińska et al. 2008). The species is classified as Vulnerable under criterion A4ce on the Irish Red List No. 2 (Non-Marine Molluscs) (Byrne et al. 2009). It is also listed as Vulnerable on the Red List of threatened species of the Czech Republic (Farkač et al. 2005), and as Endangered on the Norwegian Red List (Byrne et al. 2009).
Although the species is widespread at present, it has been declining in parts of the range. The major threat identified in some areas is due to new invasions of non-native species, and hence further research on the impact of non-native species on Anodonta anatina is urgently needed to determine the likely longer-term threats they present. Following this it can be determined whether further actions are necessary.
Data is required to establish whether the species meets the decline threshold of more than 30% over the last 25 years. It can then also be determined whether further actions are necessary.

Citation: Killeen, I. & Aldridge, D. 2011. Anodonta cygnea. The IUCN Red List of Threatened Species 2011: e.T156066A4907255. . Downloaded on 25 September 2018.
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