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 deertoe attracts and if it recognizes its fish host is unknown.
Glochidia respond to both 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
Truncilla donaciformis is not currently considered for conservation status lists.
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 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.
Lab trials have not been conducted to determine the deer toe's fish host. Natural infestations were observed for freshwater drum and sauger, but metamorphosis has not been observed on either species.
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
The deer toe is found throughout the Mississippi river system and in the the St. Lawrence system. Its range extends from western Pennsylvania to Michigan and Minnesota, south though eastern Iowa, eastern Kansas, eastern Texas, through Louisiana, Alabama and Tennessee.
In the lower peninsula in western Michigan, T. truncata is found in the Grand River system, the Kalamazoo and Black and St. Joseph (Lake Michigan) Rivers. In the southeastern part of the state it is found in Lake Erie and tributaries, including the Belle, Black, Huron, and Raisin Rivers.
Biogeographic Regions: nearctic (Native )
In Michigan, Truncilla truncata is generally found in Lake Erie or the lower stretches of rivers. In general it is found in lakes and medium to large rivers, usually in mud, sand and/or gravel.
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 deertoe is up to 5.1 cm (2 inches) long , and is triangular, moderately inflated, and fairly thick. The anterior end is uniformly rounded, the posterior end bluntly pointed or truncated. The dorsal margin is rounded. The ventral margin is broadly rounded, and straight to concave toward the posterior end. A shallow sulcus is anterior to the posterior ridge, which is sharply angled and prominent. Females and males are not as easily distinguished as other members of the subfamily Lampsilinae.
Umbos are prominent and raised slightly above the hinge line. The beak sculpture is fine, with three to five double-looped ridges.
The periostracum (outer shell layer) is yellow, green, to yellow-brown. Usually numerous green rays are present, varying in widths and shape. Rays may be fine broken lines or V-shaped zigzag markings. Older specimens tend to be more brown.
On the inner shell, the left valve has two pseudocardinal teeth, which are tall, rough, notched and compressed. The two lateral teeth are slightly curved, short and striated. The right valve has one erect, triangular, notched pseudocardinal tooth. Anterior to this tooth is a smaller (lamellar) tooth. The one lateral tooth is arched, high and striated.
The beak cavity is shallow. Although the nacre is white, occasionally it is has a pink or salmon tint and is iridescent at the posterior end.
In Michigan, this species can be confused with the fawnsfoot. The fawnsfoot is more elongated and has a smoother dorsal ridge.
Range length: 5.1 (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. 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.
Truncilla truncata is a long-term brooder. In the Huron River, it was ravid from early August to early July. After it releases its glochidia in early July, it likely spawns.
Breeding interval: The deertoe breeds once in the warmer months of the year.
Breeding season: In Michigan, the breeding season is probably mid-July to early 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)
Truncilla truncata, the deertoe, is a species of freshwater mussel, an aquatic bivalve mollusk in the family Unionidae.
Deertoe are found in the Mississippi River drainage system and in tributaries of Lake Erie and Lake St. Clair.[1] T. truncata is a state endangered species in Virginia.[2] It is designated by the state of Kansas as a "species in need of conservation".[3]
Deertoe have generalist habitat preferences and are found in both lakes and rivers.[1]
Deertoe are believed to be bradytictic, with a gestation period of approximately 10 months.[4] Hosts for their glochidia include freshwater drum (Aplodinotus grunniens) and sauger (Sander canadensis).[1]
Truncilla truncata, the deertoe, is a species of freshwater mussel, an aquatic bivalve mollusk in the family Unionidae.
Deertoe are found in the Mississippi River drainage system and in tributaries of Lake Erie and Lake St. Clair. T. truncata is a state endangered species in Virginia. It is designated by the state of Kansas as a "species in need of conservation".
Deertoe have generalist habitat preferences and are found in both lakes and rivers.
Deertoe are believed to be bradytictic, with a gestation period of approximately 10 months. Hosts for their glochidia include freshwater drum (Aplodinotus grunniens) and sauger (Sander canadensis).
