Unionidae

Taxobox
name = Unionidae

---

image_width = 240px
image_caption = Duck mussel, "Anodonta anatina"
regnum = Animalia
phylum = Mollusca
classis = Bivalvia
subclassis = Paleoheterodonta
ordo = Unionoida
familia = Unionidae
subdivision_ranks = Genera
subdivision = 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 [cite journal |author=Williams, J. D, M. L. Warren, K. S. Cummings, J. L. Harris, and R. J. Neves |title=Conservation Status of Freshwater Mussels of the United States and Canada|journal=Fisheries|volume=18|issue=9 |pages=6–22|year=1993 |doi=10.1577/1548-8446(1993)018<0006:CSOFMO>2.0.CO;2 |doilabel=10.1577/1548-8446(1993)0180006:CSOFMO2.0.CO;2 ] . Freshwater mussels occupy a wide range of habitats, but most often occupy lotic waters. The shell is equivalve and 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.

Genera and species

* Genus "Alasmidonta"
* Genus "Anodonta"
* Genus "Cucumerunio" Iredale, 1934
** "Cucumerunio websteri delli", McMichael & Hiscock, 1958
** "Cucumerunio websteri websteri", Simpson, 1902
* Genus "Elliptio"
* Genus "Epioblasma"
* Genus "Hyridella" Swainson, 1840
** New Zealand freshwater mussel, "Hyridella menziesi", Gray, 1843
* Genus "Lampsilis" ( [http://www.glerl.noaa.gov/pubs/photogallery/Waterlife/pages/0661.html image] )
* Genus "Lasmigona"
* Genus "Pseudanodonta"
** Depressed river mussel, "Pseudanodonta complanata"
* Genus "Pyganodon"
* Genus "Sinanodonta"
** "Sinanodonta woodiana"
* Genus "Strophitus"
* Genus "Truncilla"
* Genus "Unio"
* Genus "Utterbackia"

References

* Powell A. W. B., "New Zealand Mollusca", William Collins Publishers Ltd, Auckland, New Zealand 1979 ISBN 0-00-216906-1

External links

* [http://unionid.missouristate.edu Missouri State Unio Gallery]
* [http://ellipse.inhs.uiuc.edu/FMCS/ Freshwater Mollusk Conservation Society]
* [http://www.biosci.ohio-state.edu/~molluscs/gallery/unionidae.htm Division of Molluscs - Freshwater Mussel Collection - Unionidae]