Unionidae

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iUnionidae
Duck mussel, Anodonta anatina
Duck mussel, Anodonta anatina
Scientific classification
Kingdom: Animalia
Phylum: Mollusca
Class: Bivalvia
Subclass: Paleoheterodonta
Order: Unionoida
Family: Unionidae
Genera

See text for genera and species.

Unionidae is a family of freshwater mussels, found world-wide living buried in mud, silt or sand in rivers, streams and lakes. The shell is equivalve, nacreous and with a thick periostracum. The hinge mostly with two cardinals and two posterior lamellar teeth.

All Unionidae live half-buried in the sediment, their siphons sticking out. They pump water throught the inflow and outflow siphons, obtaining oxygen and food.

Unionidae have a remarkably complex life history. All Unios are of separate sex. The sperm is excreted through the male’s outflow opening and ingested by the female through the inflow opening. Fertilized eggs move from the gonads to the gills (marsupia) where they further ripen and turn into the first larval stage, the glochidium. Mature glochidia are ejected by the female and then attach to the gills, fins or skin of a host fish. A cyst is quickly formed around the glochidia and they stay on the fish for several weeks or months before they fall of as juvenile mussels which bury themselves in the sediment.

[edit] Genera and species

[edit] References

  • A B Powell, New Zealand Mollusca, (William Collins Publishers Ltd, Auckland, New Zealand 1979) ISBN 0-00-216906-1
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