The genus Epioblasma was formerly known (synonomous) as Dysnomia. This species has also been called Plagiola triquetra.
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 spike 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
Epioblasma triquetra is on state endangered lists in Illinois, Indiana, Michigan, Missouri, Ohio, Virginia and Wisconsin. In Minnesota it is listed as threatened. In Canada it is federally Endangered under the Species At Risk Act. This species is currently under consideration for federal listing.
US Federal List: no special status
CITES: 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.
Fish hosts are determined by looking at both lab transformations 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.
In lab trials, Epioblasma triquetra metamorphosed on the logperch, the black-sided darter, the Ozark sculpin, the banded sculpin, and the black spotted topminnow. The logperch is likely its main host species, given the distribution and numbers of glochidia that successfully transform on the logperch.
Ecosystem Impact: parasite
Species Used as Host:
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
The snuffbox mussel is found from western New York and souther Ontario, west to Wisconsin, Iowa and eastern Nebraska, south to Oklahoma, and east to northern Alabama. Within this range it is found in Tennessee, West Virginia, and the Ohio River drainage.
In Michigan this species is found in southeastern Michigan rivers of the Lake Erie drainage, except for the Raisin River. In western Michigan it was historically found in parts of the St. Joseph (Michigan) and Muskegon Rivers. One shell was collected from the Kalamazoo River, although a live individual has not been found. Recent populations have been found in the Grand River. Other museum specimens were collected from the Cass and Chippewa Rivers in the 1930s.
Biogeographic Regions: nearctic (Native )
In Michigan, Epioblasma triquetra is found in small- to medium-sized rivers, 7 to 23 m wide. In the southeastern part of Michigan, it is more common in streams between lakes. Its fish host, the logperch, Percina caprodes reproduces in both rivers and lakes, and populations of E. triquetra have been also been found in lakes. However, the invasion of the zebra mussel Dreissena polymorpha, has decimated most lake populations of the snuffbox in southeastern Michigan.
Habitat Regions: freshwater
Aquatic Biomes: rivers and streams
The age of mussels can be determined by looking at annual rings on the shell. Demographic data in Michigan for this species suggest they may live from 14-20 years.
The snuffbox is up to 6.4 cm (2.5 inches) long , and is triangular or elongated in shape. The shell is uniformly solid, and inflated. The anterior end is rounded. Males have a truncated posterior end and females have a more expanded posterior end. The dorsal and ventral margins are straight to slightly curved. Females in general are smaller and can be distinguished from males by the ribs and teeth-like sculpture at the posterior end.
Umbos are broad and slightly raised above the hinge line. The beak sculpture is has three to four double-looped bars, although these may be worn and faint.
The periostracum (outer shell layer) is smooth, yellow to yellow-green. The shells also have dark green rays with blotches or chevron markings.
On the inner shell, the left valve has two pseudocardinal teeth, which are high, thin and triangular. The two lateral teeth are short, slightly curved, and slightly striated. The right valve has one high, triangular, thin, triangular pseudocardinal tooth. The one right lateral tooth is short, slightly curved and slightly striated.
The beak cavity is moderately to fairly deep. Although the nacre is white and iridescent at the posterior end.
In Michigan, this species can be confused with the slippershell, and deertoe. The snuffbox is generally smaller, and females are tooth-like at the posterior end. Slippershells are smaller (therefore growth lines are closer together) and lack the black blotches and chevrons. The deertoe is generally larger than the snuffbox and is more rounded in shape.
Range length: 6.4 (high) cm.
Other Physical Features: ectothermic ; heterothermic ; bilateral symmetry
Sexual Dimorphism: sexes shaped differently
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. In Michigan, reproduction of E. triquetra probably occurs from mid-July to August when water temperatures are from 21 to 27 degrees C. 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 larvae, called glochidia.
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.
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)
Epioblasma triquetra, common name the snuffbox mussel, is a species of freshwater mussel, a mollusk in the family Unionidae. It is native to eastern North America, where it is a listed as an endangered species in both Canada and the United States.[1][2][4]
This species lives in the Great Lakes system and Mississippi River system. Its natural habitat is riffles and shoals of rocky rivers, and the shores of lakes with wave activity. This species is declining throughout its range due to habitat destruction, siltation, pollution, and competition with invasive species.[1] Despite this, it remains the most widespread and abundant member of the genus Epioblasma, of which the other members are now either extinct or severely imperiled.[5]
All Unionidae are known to use the gills, fins, or skin of a host fish for nutrients during the larval glochidia stage. In 2004, it was discovered that female Epioblasma triquetra mussels lure the unsuspecting fish towards them, then quickly clamp onto the head of the host fish and pump the glochidia larvae into their gills. The primary confirmed host fish for Epioblasma triquetra was found to be the common logperch, due to it being able to survive this violent encounter.[6][7]
Epioblasma triquetra, common name the snuffbox mussel, is a species of freshwater mussel, a mollusk in the family Unionidae. It is native to eastern North America, where it is a listed as an endangered species in both Canada and the United States.
