Potamilus ohiensis

Geographic Range

The pink papershell is generally found in the Mississippi drainage, ranging from western New York to southern Michigan to eastern Texas.

In Michigan this species was recorded from the Grand River and Pentwater Lake. (Burch, 1975)


The pink papershell is usually found in rivers and large streams, and rarely small creeks. The current where it is found is fairly swift and substrates vary from silt, mud, or sand. (Cummings and Mayer, 1992; Watters, 1995)

  • Aquatic Biomes
  • rivers and streams

Physical Description

The pink papershell is up to 17.8 cm (7 inches) long , and is oblong and ovate in shape. The shell is usually fairly thin, fragile and compressed. The anterior end is sharply rounded, the posterior end also sharply rounded. The dorsal margin is straight and the ventral margin is uniformly curved. Behind the umbo and towards the posterior is a large wing. Aneriorly, there is also a wing, but it is smaller and usually missing in older individuals.

Umbos are flattened, not raised above the hinge line, and are slightly on the anterior end of the shell. The beak sculpture has three or four fine, small, nodulose, thickened ridges.

The periostracum (outer shell layer) is shiny, tan or olive-green to dark brown. Older specimens tend to be darker brown.

On the inner shell, the left valve has two pseudocardinal teeth, which are thin and divergent. The anterior tooth is anterior to the umbo. The two lateral teeth are curved and short. The right valve has one thin, long pseudocardinal tooth. Anterior to this tooth is a low, long, ridgelike denticle (nacreous swelling). The one lateral tooth is short and fairly high.

The beak cavity is shallow. The nacre is light purple to pink and iridescent at the posterior end.

In Michigan, this species can be confused with the fragile papershell and the pink heelsplitter. The fragile papershell is generally light yellow and darker toward the umbos. The fragile papershell is also a little more oval in shape and generally has less of a prominent wing. The pink heelsplitter is usually much darker, has a more prominent wing, and rays. The nacre is also uniformly purple. (Cummings and Mayer, 1992; Oesch, 1984; Watters, 1995)

  • Sexual Dimorphism
  • sexes alike
  • Range length
    17.8 (high) cm
    7.01 (high) in


Fertilized eggs are brooded in the marsupia (water tubes) up to 11 months, where they develop into larvae, called glochidia. The glochidia are then released into the water where they must attach to the gill filaments and/or general body surface of the host fish. After attachment, epithelial tissue from the host fish grows over and encapsulates the glochidium, usually within a few hours. The glochida then metamorphoses into a juvenile mussel within a few days or weeks. After metamorphosis, the juvenile is sloughed off as a free-living organism. Juveniles are found in the substrate where they develop into adults. (Arey, 1921; Lefevre and Curtis, 1910)


Age to sexual maturity for this species is unknown. In Michigan, reproduction of E. triquetra probably occurs from mid-July to August when water temperatures are from 21 to 27 degrees C. In general, gametogenesis in unionids is initiated by increasing water temperatures. The general life cycle of a unionid, includes open fertilization. Males release sperm into the water, which is taken in by the females through their respiratory current. The eggs are fertilized in the suprabranchial chambers, then pass into water tubes of the gills, where they develop into larvae, called glochidia. (Lefevre and Curtis, 1912; ; Watters, 1995)

  • Breeding interval
    The snuffbox mussel breeds once in the warmer months of the year.
  • Breeding season
    In Michigan, the breeding season is mid-July to August.
  • Average gestation period
    10 months

Females brood fertilized eggs in their marsupial pouch. The fertilized eggs develop into glochidia. There is no parental investment after the female releases the glochidia.

  • Parental Investment
  • pre-fertilization
    • provisioning
  • pre-hatching/birth
    • provisioning
      • female


Mussels in general are rather sedentary, although they may move in response to changing water levels and conditions. Although not thoroughly documented, the mussels may vertically migrate to release glochidia and spawn. Often they are found buried under the substrate. (Oesch, 1984)

Communication and Perception

Three large, distinct ganglia make up the bilateral nervous system of a bivalve. Cerebropleural ganglia are anterior and give rise to the visceral (gut) ganglia and pedal (foot) ganglia.

The middle lobe of the mantle edge has most of a bivalve's sensory organs. Paired statocysts, which are fluid filled chambers with a solid granule or pellet (a statolity) are in the mussel's foot. The statocysts help the mussel with georeception, or orientation.

Unionids in general may have some form of chemical reception to recognize fish hosts. Mantle flaps in the lampsilines are modified to attract potential fish hosts. How the snuffbox attracts its main fish host, the logperch, is unknown. However, the mantle flaps are darkened and may resemble food for the logperch.

Glochidia respond to both touch, light and some chemical cues. In general, when touched or a fluid is introduced, they will respond by clamping shut. (Arey, 1921; Brusca and Brusca, 2003; Watters, 1995)

Food Habits

In general, unionids are filter feeders. The mussels use cilia to pump water into the incurrent siphon where food is caught in a mucus lining in the demibranchs. Particles are sorted by the labial palps and then directed to the mouth.

Mussels have been cultured on algae, but they may also ingest bacteria, protozoans and other organic particles. (Watters, 1995)


Unionids in general are preyed upon by muskrats, raccoons, minks, otters, and some birds. Juveniles are probably also fed upon by freshwater drum, sheepshead, lake sturgeon, spotted suckers, redhorses, and pumpkinseeds.

Unionid mortality and reproduction is affected by unionicolid mites and monogenic trematodes feeding on gill and mantle tissue. Parasitic chironomid larvae may destroy up to half the mussel gill. (Cummings and Mayer, 1992; Watters, 1995)

Ecosystem Roles

Glochidia were found to metamorphose on the freshwater drum in the lab. Natural infestations have also been observed. (Brady, et al., 2004)

Species Used as Host

Economic Importance for Humans: Positive

Mussels are ecological indicators. Their presence in a water body usually indicates good water quality.

Conservation Status

Potamilus ohiensis currently has no special conservation status.

Other Comments

Potamilus ohiensis was formerly known as Leptodea laevissima.


Renee Sherman Mulcrone (author).



living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.


uses smells or other chemicals to communicate


an animal that mainly eats decomposed plants and/or animals


particles of organic material from dead and decomposing organisms. Detritus is the result of the activity of decomposers (organisms that decompose organic material).


animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

external fertilization

fertilization takes place outside the female's body


union of egg and spermatozoan


a method of feeding where small food particles are filtered from the surrounding water by various mechanisms. Used mainly by aquatic invertebrates, especially plankton, but also by baleen whales.


mainly lives in water that is not salty.


having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.


A large change in the shape or structure of an animal that happens as the animal grows. In insects, "incomplete metamorphosis" is when young animals are similar to adults and change gradually into the adult form, and "complete metamorphosis" is when there is a profound change between larval and adult forms. Butterflies have complete metamorphosis, grasshoppers have incomplete metamorphosis.


having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.


an organism that obtains nutrients from other organisms in a harmful way that doesn't cause immediate death


photosynthetic or plant constituent of plankton; mainly unicellular algae. (Compare to zooplankton.)


an animal that mainly eats plankton

seasonal breeding

breeding is confined to a particular season


remains in the same area


reproduction that includes combining the genetic contribution of two individuals, a male and a female


uses touch to communicate


movements of a hard surface that are produced by animals as signals to others


uses sight to communicate


reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.


Arey, L. 1921. An experimental study on glochidia and the factors underlying encystment. J. Exp. Zool., 33: 463-499.

Brady, T., M. Hove, C. Nelson, R. Gordon, D. Hornbach, A. Kapuscinski. 2004. Suitable host fish determined for hickorynut and pink heelsplitter. Ellipsaria, 6: 14-15.

Brusca, R., G. Brusca. 2003. Invertebrates. Sunderland, Massachusetts: Sinauer Associates, Inc..

Burch, J. 1975. Freshwater unionacean clams (Mollusca: Pelecypoda) of North America. Hamburg, Michigan: Malacological Publications.

Cummings, K., C. Mayer. 1992. Field guide to freshwater mussels of the Midwest. Champaign, Illinois: Illinois Natural History Survey Manual 5. Accessed August 25, 2005 at http://www.inhs.uiuc.edu/cbd/collections/mollusk/fieldguide.html.

Lefevre, G., W. Curtis. 1912. Experiments in the artificial propagation of fresh-water mussels. Proc. Internat. Fishery Congress, Washington. Bull. Bur. Fisheries, 28: 617-626.

Lefevre, G., W. Curtis. 1910. Reproduction and parasitism in the Unionidae. J. Expt. Biol., 9: 79-115.

Oesch, R. 1984. Missouri naiades, a guide to the mussels of Missouri. Jefferson City, Missouri: Missouri Department of Conservation.

Watters, G. 1995. A guide to the freshwater mussels of Ohio. Columbus, Ohio: Ohio Department of Natural Resources.

van der Schalie, H. 1938. The naiad fauna of the Huron River, in southeastern Michigan. Miscellaneous Publications of the Museum of Zoology, University of Michigan, 40: 1-83.