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 the purple wartyback attracts or if it recognizes 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
Cyclonaias tuberculata is listed as Endangered in Wisconsin, Threatened in Illinois, Iowa and Minnesota, and Significantly Rare in North Carolina. In Michigan it is listed as Special Concern. The IUCN Red List considers this species Lower Risk, Near Threatened.
US Federal List: no special status
CITES: no special status
IUCN Red List of Threatened Species: lower risk - near threatened
Fertilized eggs are brooded in the marsupia (water tubes) up to three 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 the glochidium, usually within a few hours. The glochidium 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.
Positive Impacts: body parts are source of valuable material
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.
In lab trials, Cyclonaias tuberculata metamorphosed on the black bullhead, the yellow bullhead, the channel catfish, and the flathead catfish. These species generally co-exist with the purple wartyback, but no natural infestations have been observed.
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 purple wartyback is found in the Mississippi drainage, the Lake St. Clair drainage, the Detroit River and Lake Erie.
In Michigan C. tuberculata is mainly found in rivers of the Lake Erie drainage and the Kalamazoo, St. Joseph, Thornapple and Grand Rivers of the Lake Michigan drainage. It has also been recorded in the Menominee River in the upper peninsula.
Biogeographic Regions: nearctic (Native )
Cyclonaias tuberculata is mainly found in rivers where definite riverine conditions with a stronger current exist. In Michigan and Ohio it may be found in smaller rivers. In the St. Joseph River, it was found in slower moving waters that were fairly clear. In general the purple wartyback is found in better quality streams.
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 purple wartyback is up to 12.7 cm (5 inches) long, and is round. The shell is fairly thick, heavy and compressed. The anterior end is rounded, the posterior end somewhat angled. The dorsal margin is straight to slightly rounded and the ventral margin is broadly rounded.
Umbos are low and only slightly raised above the hinge line. The beak sculpture has several wavy ridges.
The periostracum (outer shell layer) has several pustules, and ridges on the dorsal wing. Younger specimens are yellowish to greenish brown, while older specimens tend to be more uniformly brown.
On the inner shell, the left valve has two widely divergent, serrated, thin and low pseudocardinal teeth. The two lateral teeth are striated, and straight to slightly curved. The right valve has one heavy, triangular serrated pseudocardinal tooth with a small tooth on either side. The right, single lateral tooth is slightly curved and striated.
The beak cavity is very deep. The nacre is almost always purple, and rarely white.
In Michigan, this species can be confused with the pimpleback. The pimpleback usually has a prominent green ray, lacks a dorsal wing and purple nacre.
Range length: 12.7 (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.
The purple wartyback is a short-term brooder. On the Huron River, it was gravid from late May to early August. It likely spawns in early May.
Breeding interval: The purple wartyback breeds once in the warmer months of the year.
Breeding season: In Michigan, the breeding season is probably early May.
Range gestation period: 2.5 (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)
Rotundaria tuberculata, commonly called the purple wartyback, is a freshwater mussel, an aquatic bivalve mollusk.
This species is native to eastern North America, generally in the Mississippi River drainage, where it is wide-ranging. It is still common in many areas, particularly in the southern part of its range.[2]
It was formerly classified as the sole species in the genus Cyclonaias, but in 2012 it was moved to Rotundaria based on genetic evidence.[3]
Rotundaria tuberculata, commonly called the purple wartyback, is a freshwater mussel, an aquatic bivalve mollusk.
This species is native to eastern North America, generally in the Mississippi River drainage, where it is wide-ranging. It is still common in many areas, particularly in the southern part of its range.
It was formerly classified as the sole species in the genus Cyclonaias, but in 2012 it was moved to Rotundaria based on genetic evidence.
