Paper Pondshell (Paper Floater)

paper pondshell
Scientific Name
Utterbackia imbecillis
Unionidae (freshwater mussels) in the phylum Mollusca

Very thin, elongate shell; oblong and inflated in adults. Umbo not raised above the very flat hinge line. Epidermis is shiny, yellow to green with faint yellow to green rays; young are beautiful bright green, with thin glossy shells. Inside shell beak cavity shallow to absent; teeth absent; nacre (lining) iridescent white to bluish-white.

Similar species: Small giant floaters are distinguished by umbo distinctly raised above the hinge line.


Adult length: 1-4 inches.

Where To Find
image of Paper Pondshell Paper Floater Distribution Map

Statewide but sporadic; sometimes locally abundant.

Quiet water in ponds, lakes, reservoirs, sloughs and streams. Found in rivers as large as the Mississippi and as small as the Maries. In rivers, it favors quiet backwaters and eddies in silt or a mix of silt and fine sand.

Algae and fine particles of decaying organic matter; extracts nutrients and oxygen from water drawn into the body cavity through a specialized gill called the incurrent siphon; sediment and undigested waste are expelled through the excurrent siphon.

Fairly common, although degrading water quality and watershed destabilization interfere with the survival of this and all freshwater mussels.

Life Cycle

As with most mussels, males release sperm into water, and females downstream siphon sperm into the gill chamber, where eggs are fertilized. Eggs mature into larvae and discharge into the water and attach to host fish. The growing mussel later breaks away and floats to the stream bottom, and the cycle repeats. This species, unlike most other freshwater mussels, is hermaphrodic: An individual can produce both eggs and sperm, and can also fertilize itself.

Mussels are excellent biological indicators of water quality because they are long-lived and relatively immobile, accumulating contaminants in water that can be scientifically analyzed.

Mussels act as nature's “vacuum cleaners,” filtering and cleansing polluted waters. They are also an important food source for other species in the aquatic environment.

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Similar Species
About Aquatic Invertebrates in Missouri
Missouri's streams, lakes, and other aquatic habitats hold thousands of kinds of invertebrates — worms, freshwater mussels, snails, crayfish, insects, and other animals without backbones. These creatures are vital links in the aquatic food chain, and their presence and numbers tell us a lot about water quality.