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.
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
Pyganodon lacustris is not listed in Michigan or any other states.
IUCN Red List of Threatened Species: no special status
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
There are no significant negative impacts of mussels on humans.
Mussels are ecological indicators. Their presence in a water body usually indicates good water quality.
While freshwater mussels require a host fish for metamorphosis, the hosts for Pyganodon lacustris are unknown.
Ecosystem Impact: parasite
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.
Plant Foods: algae; phytoplankton
Other Foods: detritus ; microbes
Foraging Behavior: filter-feeding
Primary Diet: planktivore ; detritivore
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.
Biogeographic Regions: nearctic (Native )
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
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.
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.
Range length: 20 (high) cm.
Other Physical Features: ectothermic ; heterothermic ; bilateral symmetry
Sexual Dimorphism: sexes alike
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.
Known Predators:
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.
Breeding interval: This species breeds once in the warmer months of the year.
Breeding season: In Michigan, the breeding season is probably in the summer months.
Range gestation period: 10 (high) months.
Key Reproductive Features: seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization (Internal ); 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)
Pyganodon lacustris is a species of freshwater mussel, an aquatic bivalve mollusk in the family Unionidae, the river mussels. It is endemic to the United States, where it is known to occur in Illinois, Ohio, Michigan, New York, Indiana and Wisconsin. It may also occur in the Great Lakes and into Canada, however its full range has not been fully assessed.[1] It is commonly called the lake floater.[2]
Pyganodon lacustris varies in size with the largest found to be around 20 centimeters (8 inches)[3] with an average of around 10 centimeters (4 inches). They have an elliptical shape and is generally long and thin. The ventral is straight to slightly curved and color ranges from yellow-green in adolescence to dark brown or black in adulthood.[4]
Pyganodon lacustris is a species of freshwater mussel, an aquatic bivalve mollusk in the family Unionidae, the river mussels. It is endemic to the United States, where it is known to occur in Illinois, Ohio, Michigan, New York, Indiana and Wisconsin. It may also occur in the Great Lakes and into Canada, however its full range has not been fully assessed. It is commonly called the lake floater.
