The pink heelsplitter was formerly known as Potamilus alatus.
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. Mantle flaps in the lampsilines are modified to attract potential fish hosts. How the pink heelsplitter recognizes and/or 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
Potamilus alatus is listed as Endangered in Vermont.
US Federal List: no special status
CITES: no special status
IUCN Red List of Threatened Species: lower risk - least concern
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.
Fish hosts are determined by looking at both lab metamorphosis and natural infestations. Looking at both is necessary, as lab transformations from glochidia to juvenile may occur, but the mussel may not actually infect a particular species in a natural situation. Natural infestations may also be found, but glochidia will attach to almost any fish, including those that are not suitable hosts. Lab transformations involve isolating one particular fish species and introducing glochidia either into the fish tank or directly inoculating the fish gills with glochidia. Tanks are monitored and if juveniles are later found the fish species is considered a suitable host.
Glochidial metamorphosis has not been tested for any fish species yet. However, natural infestations of Potamilus alatus glochidia on the freshwater drum (also called sheephead) have been observed.
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.
Plant Foods: algae; phytoplankton
Other Foods: detritus ; microbes
Foraging Behavior: filter-feeding
Primary Diet: planktivore ; detritivore
The pink heelsplitter occurs in the Mississippi drainage from Pennsylvania, south to northern Alabama and Mississippi, west to eastern Oklahoma and north thorough the eastern Dakotas. In Canada it is found in the Red River of the North and the Winnipeg river. In the St. Lawrence drainage, it is found from Lake Huron to Lake Champlain.
In Michigan Potamilus alatus is found at the lower stretches of rivers in the lower peninsula, and in Lakes Erie and St. Clair.
Biogeographic Regions: nearctic (Native )
The pink heelsplitter can be found in various types of substrate, and in slower moving waters.
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.
The pink heelsplitter is up to 20.3 cm (8 inches) long , and is elongate and somewhat rectangular in shape. The shell is large and laterally compressed. A large wing is usually present posterior to the umbos. The anterior end is sharply rounded, the posterior end broadly rounded and somewhat angled. The angle of the dorsal margin depends on the shape of the wing, and the ventral margin is straight to gently curved.
Umbos are low, being raised only slightly above the hinge line. The beak sculpture is fine, with concentric lines.
The periostracum (outer shell layer) is smooth, dark greek or brown with green rays. Older specimens tend to be more brown or black.
On the inner shell, the left valve has two pseudocardinal teeth, which are thin, erect and knobby. The two lateral teeth are short, thin, slightly curved and roughened. The right valve has one erect, triangular, striated pseudocardinal tooth. Anterior to this tooth is a smaller denticle (nacreous swelling). The one lateral tooth is high and slightly curved.
The beak cavity is shallow. The nacre is purple throughout and iridescent throughout, or mainly at the posterior end.
In Michigan, this species can be confused with the white heelsplitter. The white heelsplitter is more round or plate-like in shape.
Range length: 20.3 (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.
Potamilus alatus is a long-term brooder and probably spawns in the summer months in Michigan.
Breeding interval: The pink heelsplitter 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)
Potamilus alatus, the pink heelsplitter, is a species of freshwater mussel, an aquatic bivalve mollusk in the family Unionidae, commonly known as the river mussels.
This species is native to eastern North America. It is found in the drainages of the Ohio River, the St. Lawrence River, the Great Lakes, and the Canadian Interior Basin.
Potamilus alatus, the pink heelsplitter, is a species of freshwater mussel, an aquatic bivalve mollusk in the family Unionidae, commonly known as the river mussels.
This species is native to eastern North America. It is found in the drainages of the Ohio River, the St. Lawrence River, the Great Lakes, and the Canadian Interior Basin.
