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Mississippi National River and Recreation AreaRe-enactors in a large birchbark Voyageur canoe paddle the Mississippi River.
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Mississippi National River and Recreation Area
Threeridge
(Amblema plicata) Say, 1817
A Threeridge mussel
K.S. Cummings, Illinois Natural History Survey
Other Common Names:
Bluepoint; Purple-tip; Fluter
Habitat:
Small to large rivers and impoundments in mud, sand, or gravel.
Length:
Up to 7 inches (17.8 cm).
Outer Shell Color:
Brown, dark green, or black in adults. Young mussels are green, yellowish-green, or light brown.
Inner Shell Color:
Pearly white, often with staining. Iridescent or purple color on the long end of the shell.
Shell Thickness:
Thick. Heavy.
Shell Outline:
Slightly longer than wide and oval-shaped or rounded. The shell edge is straight along the point where the two shell halves join. The end of the shell farthest from the beak comes to a rounded point.
Shell Surface:
Wavy. There are three low ridges (rarely four), spaced equally apart along the shell surface. All ridges point in the direction of the longest end of the shell (measured from the beak, which is the swelling above where the two shell halves join). The outer surface along the shell end near the beak has no ridges. Threeridge specimens without ridges do occur but are rare and can be easily mistaken for the endangered Higgins’ Eye.
Scientific Description:
Adult shell brown or black. Juvenile shell tending toward green. Heavy, moderately large shell. Beak sculpture: several concentric rings not extending onto disc. Adult shell with approx. Three wide ridges.
Similar Looking Mussels:
Washboard; Rockshell.
Host Fish:
Northern Pike, Shortnose Gar, Pumpkinseed, Bluegill, Largemouth Bass, White Bass, Yellow Perch, White Crappie
Distribution:
Widespread and common throughout most of its range.
Minnesota State Listing:
None.
Federal Listing:
None.
Lock and Dam Number 1 from a long distance.  

Did You Know?
At Lake Itasca, the elevation of the Mississippi River is 1,475 feet above sea level. It drops to sea level at the Gulf of Mexico. More than half of that drop occurs within the state of Minnesota.

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Last Updated: September 20, 2006 at 14:44 EST