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.
- Habitat Regions
- freshwater
- 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.
- Other Physical Features
- ectothermic
- heterothermic
- bilateral symmetry
- 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.
- Development - Life Cycle
- metamorphosis
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.
- Key Reproductive Features
- seasonal breeding
- gonochoric/gonochoristic/dioecious (sexes separate)
- sexual
- fertilization
- viviparous
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
-
provisioning
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.
- Communication Channels
- chemical
- Perception Channels
- visual
- tactile
- vibrations
- chemical
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.
- Primary Diet
- planktivore
- detritivore
- Plant Foods
- algae
- phytoplankton
- Other Foods
- detritus
- microbes
- Foraging Behavior
- filter-feeding
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.
- Ecosystem Impact
- parasite
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.
Additional Links
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.
- 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.