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Mississippi National River and Recreation AreaA view of the Mississippi River from the bluffs south of the Twin Cities.
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Mississippi National River and Recreation Area
Giant Floater
(Pyganodon grandis) Say, 1829
A Giant Floater mussel
K.S. Cummings, Illinois Natural History Survey
Other Common Names:
Floater; Stout floater; Papershell; Hogshell; Slopbucket.
Habitat:
Typically, ponds, lakes, and sluggish mud-bottomed pools of creeks and rivers.
Length:
Very large. Up to 10 inches (25.4 cm).
Outer Shell Color:
Varies: can be yellow, green, or brown. May have 3-5 darker rings that are off center. Green rays are especially common in young mussels.
Inner Shell Color:
Varies: may be silvery white, cream, pink, salmon, or copper-colored.
Shell Thickness:
Thin, especially in young mussels.
Shell Outline:
The entire shell outline is shaped somewhat like a stretched-out egg.The tip and base of the egg form the shell edges on either side of point where the 2 shell halves meet.
Shell Surface:
The entire outer shell surface looks somewhat swollen, and feels smooth. The beak (above where the 2 shell halves join) forms the highest point of the shell surface. The outer surface has many fine growth rings (they look like the lines were made by dragging a fine toothed comb along the surface). The growth rings are pressed close together behind the beak. 3-5 darker, enlarged growth rings are spaced out along the shell's surface.
Scientific Description:
Shell yellow, green or brown often with green rays. Very large. Inflated, elongate-suboval. Ventral margin convex (outward) or straight. Somewhat prominent beaks. Beak sculptured with several double-looped bars.
Similar Looking Mussels:
Flat Floater, Paper Pondshell, Cylindrical Papershell, Strange Floater.
Host Fish:
Skipjack Herring, Rock Bass, Yellow Bullhead, Freshwater Drum (Sheephead), Whitesucker, Common Carp, Johnny Darter .
Distribution:
Widespread and common.
Minnesota State Listing:
None.
Federal Listing:
None.
A slow and shallow section of Itaska.  

Did You Know?
At the headwaters of the Mississippi, the average surface speed of the water is 1.2 miles per hour. People typically walk 3 miles per hour.

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Last Updated: May 05, 2008 at 10:36 EST