Pyganodon lacustris

Features
By Renee Sherman Mulcrone

Geographic Range

Pyganodon lacustris is found in the St. Lawrence drainages, upper Susquehanna and Hudson, upper Mississippi, and southern Hudson Bay drainages of North America.

In Michigan, specimens have been collected from lakes in the northern part of the lower peninsula.

Habitat

Pyganodon lacustris is mainly found in lakes, and seldom in rivers. Substrates where it is found include mud bottoms.

  • Aquatic Biomes
  • rivers and streams

Physical Description

Pyganodon lacustris is up to about 20 cm (8 inches) long , and is long-ovate or elliptical in shape. The shell is usually fairly thin and inflated. The anterior end is rounded, the posterior end is elongate, pointed and biangulate. The dorsal margin is straight, slightly sloping at each end, and the ventral margin is slightly rounded.

Umbos are full and low, being raised only slightly above the hinge line, and situated toward the anterior end of the shell. The beak sculpture consists of 4-5 irregularly looped bars.

The periostracum (outer shell layer) is yellow to yellow-olive with faint rays.

On the inner shell, the left valve lacks pseudocardinal and lateral teeth . There is a slight thickening sometimes where the lateral tooth would be.

The beak cavity is shallow. The nacre is bluish-white or reddish brown and iridescent.

In Michigan, this species can be confused with the giant floater . In general, Pyganodon lacustris is more elongate.

  • Sexual Dimorphism
  • sexes alike

Development

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 a glochidium, usually within a few hours. The glochidia 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.

Reproduction

Age to sexual maturity for this species is unknown. Unionids are gonochoristic (sexes are separate) and viviparous. The glochidia, which are the larval stage of the mussels, are released live from the female after they are fully developed.

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 internally fertilized in the suprabranchial chambers, then pass into water tubes of the gills, where they develop into glochidia.

Pyganodon lacustris is likely a long-term brooder and spawns in summer in Michigan.

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

Lifespan/Longevity

The age of mussels can be determined by looking at annual rings on the shell. However, no demographic data on this species has been recorded.

Behavior

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.

Communication and Perception

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.

Mussels are heterothermic, and therefore are sensitive and responsive to temperature.

Unionids in general may have some form of chemical reception to recognize fish hosts. How Pyganodon lacustris attracts its fish host is unknown.

Glochidia respond to touch, light and some chemical cues. In general, when touched or a fluid is introduced, they will respond by clamping shut.

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.

The parasitic glochidial stage absorbs blood and nutrients from hosts after attachment. Mantle cells within the glochidia feed off of the host’s tissue through phagocytocis.

Predation

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.

Ecosystem Roles

While freshwater mussels require a host fish for metamorphosis, the hosts for Pyganodon lacustris are unknown.

Economic Importance for Humans: Positive

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

Economic Importance for Humans: Negative

There are no significant negative impacts of mussels on humans.

Conservation Status

Pyganodon lacustris is not listed in Michigan or any other states.

Other Comments

Little is known about the distribution or habitat of this species. Many specimens may have been identified as Pyganodon grandis . Molecular studies recently supported the status of this species.

Encyclopedia of Life

Contributors

Renee Sherman Mulcrone (author).

Nearctic

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

native range

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

freshwater

mainly lives in water that is not salty.

ectothermic

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

heterothermic

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.

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.

metamorphosis

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.

seasonal breeding

breeding is confined to a particular season

sexual

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

fertilization

union of egg and spermatozoan

internal fertilization

fertilization takes place within the female's body

viviparous

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

parasite

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

motile

having the capacity to move from one place to another.

sedentary

remains in the same area

chemical

uses smells or other chemicals to communicate

visual

uses sight to communicate

tactile

uses touch to communicate

vibrations

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

chemical

uses smells or other chemicals to communicate

phytoplankton

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

detritus

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

filter-feeding

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.

parasite

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

planktivore

an animal that mainly eats plankton

detritivore

an animal that mainly eats decomposed plants and/or animals

References

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

Barnhart, C., F. Riusech, M. Baird. 1998. Hosts of salamander mussel (Simpsonaias ambigua) and snuffbox (Epioblasma triquetra) from the Meramec River system, Missouri.. Triannual Unionid Report , 16: 34.

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 .

Hoeh, W., J. Burch. 1989. The taxonomic status of Anodonta lacustris Lea (Bivalvia:Unionidae). Walkerana , 3 (10): 263-276.

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.

Meglitsch, P., F. Schram. 1991. Invertebrate Zoology, Third Edition . New York, NY: Oxford University Press, Inc.

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.

To cite this page: Mulcrone, R. 2006. "Pyganodon lacustris" (On-line), Animal Diversity Web. Accessed {%B %d, %Y} at https://animaldiversity.org/accounts/Pyganodon_lacustris/

Last updated: 2006-05-10 / Generated: 2025-10-03 01:04

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