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Anodonta cygnea (Linnæus, 1758)
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Species name:
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Anodonta cygnea (Linnæus, 1758)
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Taxon name:
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Mytilus cygneus Linnæus, 1758
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Originally described in:
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Linnæus, C. 1758. Systema naturæ per regna tria naturæ, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Tomus I. Editio decima, reformata. - pp. [1-4], 1-824. Holmiæ. (Salvius).
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Distribution:
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N and central Europe (not Finland) to central Greece, W Russia, Ukraine, N Turkey and Caucasus
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Diagnosis:
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Shell yellowish or greenish brown, thin, not very solid, ligament long and narrow, without teeth, lower side of frontal interior margin not thickened. Embryonal shell finely striated along the growth lines, the lines reach the margin.
Differs from A. anatina in its larger shell with dorsal and ventral margins being straighter and more parallel, the growth lines of the embryonal shell are finer and less undulated, and reach the margin.
Animal like A. anatina, yellowish, greenish or light reddish, mantle large and brownish yellow, gills greyish and like gaze, foot large and darker than the rest of the body, opening for water supply short with long papillae.
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Size:
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60-120 x 120-200 x 30-60 (height) mm
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Biology:
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Lakes, old river arms, artificial lakes, needs silent waters, only rarely in running waters, usually in lowlands. Prefers muddy substrate bare of vegetation. Artificial lakes are usually reached when infected fishes are brought in, young mussels are rarely dispersed by water birds. Tolerates eutrophic conditions, but not in the last toxic stadium. In Switzerland in up to 1500 m altitude.
Animals are hermaphrodites. Host fishes for glochidia are Salmo trutta, Perca fluviatilis, Leuciscus leuciscus, Sander lucioperca and Gasterosteus aculeatus, but not Rhodus sericeus. Glochidia are mature in autumn, are released in spring (in England and in Italy), their size (0.35 x 0.35 mm) does not increase much in the rays of host fishes, until they sink down to the bottom to found new populations.
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Threatened:
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Threatened by continuous destruction of habitats, water current regulations, exaggerated pollution by fertilizers, also by natural drying out of waters.
Endangered in Austria, vulnerable in Germany (2009), almost vulnerable in Switzerland (1998), "Of Special Interest" in Spain.
In Niederösterreich (Austria) all bivalves were defined in 2002 by law as fishes and by this way taken out of any form of protection (in the Fischereiverordnung 2002 A. cygnea was defined as an artificially introduced species, there has never been any scientific evidence to support such a view).
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Family:
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Unionidae
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Higher group:
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Bivalvia
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Comments:
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Occasionally found in Spain and Portugal in artificially disturbed habitats, where infected fishes from central Europe were released.
References: Nobre 1941: 235, Falkner 1990: 264, Jungbluth 1993, Schwab 1995, Turner et al. 1998: 386, Kerney 1999: 211, Gómez Moliner et al. 2001, Pérez-Quintero et al. 2004, Reischütz 2009, Araujo et al. 2009: 56, Jungbluth & Knorre 2009: 12, Glöer & Diercking 2010: 130, Welter-Schultes 2012: 8 (range map).
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