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Swan mussel


(Anodonta cygnea)

Relationsship and features of typical shells (taxonomy)

Appearance


The shell is elongate-oval, shaped like an egg and fairly swollen. Reaches normally a total length of 12 - 16 cm (in exceptional cases up to 20 cm or more). Individuals living in stream water are often smaller. Colour shades of brown, often yellow - olive, sometimes with soft spots of green. The upper and lower margins of the shell are often almost parallel. The upper margin is straight and softly passed over to the dorsal end. The valves are equally thin, all along their heights. The umbonal rugae run parallel to the growth lines and sometimes coincide with these. The inhalent siphon is narrow with long papillae. The colour of the soft tissues is often rosy - orange. There are no hinge-teeth.

Biology


The species is mostly an inhabitant of lakes and ponds in Sweden but can also be found in slow flowing parts of rivers. It has more fastidious than the Duck mussel (A. anatina) and prefers waters more rich in nutrient. It is mostly found on muddy bottoms, where it occures down to a depth of 20 m.

Distribution


Fairly rare in Sweden. Scattered appearance ranging from Scania in the very south up to the middle part of the Country. Not present north of "Limes Norrlandicus". Very rare in the westernmost parts of Sweden.
 
Photo: Håkan Holmberg
Scientific basis: Ted von Proschwitz
Större dammussla vänster
Left valve
Större dammussla höger
Right valve
Större dammussla ovansida
Dorsal view
Större dammussla undersida
Ventral view