Cyclonaias tuberculata

Geographic Range

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 nearctic
  • native native

Habitat

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 freshwater

• Aquatic Biomes
• rivers and streams

Physical Description

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.

• Other Physical Features
• ectothermic ectothermic
• heterothermic heterothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• sexes alike

Development

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 metamorphosis

Reproduction

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.

• Key Reproductive Features
• seasonal breeding seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• fertilization fertilization
  • internal internal
• viviparous 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

Lifespan/Longevity

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.

Behavior

Mussels in general are rather sedentary, although they may move in response to changing water levels and conditions. Although not thoroughly documented, the mussels may vertically migrate to release glochidia and spawn. Often this species is buried under the substrate.

• Key Behaviors
• parasite parasite
• motile motile
• sedentary sedentary

Communication and Perception

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 chemical

• Perception Channels
• visual visual
• tactile tactile
• vibrations vibrations
• chemical chemical

Food Habits

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.

• Primary Diet
• planktivore planktivore
• detritivore detritivore

• Plant Foods
• algae
• phytoplankton phytoplankton

• Other Foods
• detritus detritus
• microbes

• Foraging Behavior
• filter-feeding filter-feeding

Predation

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.

Ecosystem Roles

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 parasite

Economic Importance for Humans: Positive

Mussels are ecological indicators. Their presence in a water body usually indicates good water quality.

• Positive Impacts
• body parts are source of valuable material

Economic Importance for Humans: Negative

There are no significant negative impacts of mussels on humans.

Conservation Status

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.

Additional Links

Encyclopedia of Life

BioKIDS Critter Catalog

Contributors

Renee Sherman Mulcrone (author).

References

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Badra, P. 2004. Special Abstract for Cyclonaias tuberculata (Purple wartyback) . Lansing, MI: Michigan Natural Features Inventory. Accessed October 04, 2005 at http://web4.msue.msu.edu/mnfi/abstracts/aquatics/Cyclonaias_tuberculata.pdf .

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Burch, J. 1975. Freshwater unionacean clams (Mollusca: Pelecypoda) of North America . Hamburg, Michigan: Malacological Publications.

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Cummings, K., C. Mayer. 1992. Field guide to freshwater mussels of the Midwest . Champaign, Illinois: Illinois Natural History Survey Manual 5. Accessed August 25, 2005 at http://www.inhs.uiuc.edu/cbd/collections/mollusk/fieldguide.html .

Graf, D. 2002. Historical biogeography and late glacial origin of the freshwater pearly mussel (Bivalvia: Unionidae) faunas of Lake Erie, North America. Occasional Papers of Mollusks , 6: 175-211.

Haag, W., M. Warren. 1997. Host fishes and reproductive biology of six freshwater mussel species from the Mobile Basin, USA. Journal of the North American Benthological Society , 16: 576-585.

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Hove, M. 2004. "Links to each state's listed freshwater mussels, invertebrates, or fauna" (On-line). Accessed September 21, 2005 at http://www.fw.umn.edu/Personnel/staff/Hove/State.TE.mussels .

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Hove, M. 1997. Ictalurids serve as suitable hosts for the purple wartyback. Triannual unionid report , 11: 4. Accessed October 01, 2005 at http://ellipse.inhs.uiuc.edu/FMCS/TUR/TUR11.html#p4 .

Hove, M.C., Engelking, R.A., Peteler, M.E, , Hove, M.C., Engelking, R.A., Peteler, M.E, Hove, M.C., Engelking, R.A., Peteler, M.E, Peterson, E.M., Kapuscinski, A.R., Sovell, L.A. and E.R. Evers. 1997. Suitable fish hosts for glochidia of four freshwater mussels. Conservation and Management of Freshwater Mussels II. Proceedings of a UMRCC Symposium, 16-18 October 1995, St. Louis, Missouri: 21-25. Accessed October 04, 2005 at http://ellipse.inhs.uiuc.edu/FMCS/Meetings/Symp1995Abs.html .

Lefevre, G., W. Curtis. 1912. Experiments in the artificial propagation of fresh-water mussels. Proc. Internat. Fishery Congress, Washington. Bull. Bur. Fisheries , 28: 617-626.

Lefevre, G., W. Curtis. 1910. Reproduction and parasitism in the Unionidae. J. Expt. Biol. , 9: 79-115.

Meglitsch, P., F. Schram. 1991. Invertebrate Zoology, Third Edition . New York, NY: Oxford University Press, Inc.

Oesch, R. 1984. Missouri naiades, a guide to the mussels of Missouri . Jefferson City, Missouri: Missouri Department of Conservation.

Watters, G. 1995. A guide to the freshwater mussels of Ohio . Columbus, Ohio: Ohio Department of Natural Resources.

van der Schalie, H. 1938. The naiad fauna of the Huron River, in southeastern Michigan. Miscellaneous Publications of the Museum of Zoology, University of Michigan , 40: 1-83.