Unionidae

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Unionidae
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 distributed world-wide, but most diverse in North America with about 297 recognized taxa[1]. Freshwater mussels occupy a wide range of habitats, but most often occupy lotic waters. The shell is equivalve and nacreous and has a thick periostracum. The hinge mostly has two cardinals and two posterior lamellar teeth.

Unionidae burrow into the substrate, with their posterior margins exposed. They pump water through the incurrent aperture, obtaining oxygen and food.

Unionidae are distinguished by a unique and complex life cycle. Most Unionids are of separate sex (although some species, such as Elliptio complanata, are known to be hermaphroditic). The sperm is ejected from the mantle cavity through the male’s excurrent aperture and taken into the female's mantle cavity through the incurrent aperture. Fertilized eggs move from the gonads to the gills (marsupia) where they further ripen and metamorph into glochidia, the first larval stage. Mature glochidia are released 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 off as juvenile mussels which bury themselves in the sediment.

[edit] Genera and species

[edit] References

  1. ^ Williams, J. D, M. L. Warren, K. S. Cummings, J. L. Harris, and R. J. Neves (1993). "Conservation Status of Freshwater Mussels of the United States and Canada". Fisheries 18 (9): 6–22. doi:10.1577/1548-8446(1993)018<0006:CSOFMO>2.0.CO;2. 

[edit] External links

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