Epioblasma obliquata

Geographic Range

Historically Epioblasma obliquata was found in the Ohio River drainage and the Detroit River, however its range has been greatly reduced to one population in Indiana.

In Michigan the white catspaw was historically found in the Detroit River and Lake Erie. One specimen was collected from the Raisin River in Monroe County. This species has not been collected in Michigan waters since the 1930s.

• Biogeographic Regions
• nearctic nearctic
  • native native

Habitat

Specific habitat requirements are unknown since this species is rare. However, populations recently found were in high gradient streams in riffles with gravel. In Michigan this species was historically found in the Detroit River and Lake Erie.

• Habitat Regions
• freshwater freshwater

• Aquatic Biomes
• rivers and streams

Physical Description

The catspaw is up to 5.1 cm (2 inches) long. Females are rectangular or quadrate while males are oval and elongate. The posterior ridge has a wide sulcus or depression between double ridges in males. The ridge is sharp and narrow in females. The shell is usually fairly solid and inflated. The anterior end is rounded, the posterior end bluntly pointed in males. Females have a posterior margin that is extended, truncated, with ribs and a medial notch. The dorsal margin is short and straight and the ventral margin is broadly curved in males and gently curved in females.

Umbos are full and even with the hinge line. Beak sculpture is double looped.

The periostracum (outer shell layer) is smooth, yellow to yellow-tan with fine green rays.

On the inner shell, the left valve has two pseudocardinal teeth , which are wide, elevated and serrated. The two lateral teeth are short and straight to slightly curved, and rough. The right valve has one wide, elevated and serrated pseudocardinal tooth.

The beak cavity is shallow. Although the nacre is white to purple it is iridescent at the posterior end. Michigan specimens have only had a white nacre.

In Michigan, this species could be confused with the northern riffleshell . The northern riffleshell is generally smaller and females lack serrations at the edge of the posterior end of the shell.

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

• Sexual Dimorphism
• sexes shaped differently

Development

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 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.

• 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

Based on growth rings on specimens, the white catspaw probably lives up to 15 years.

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 they are found 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. 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 chemical

• Perception Channels
• visual visual
• infrared/heat infrared/heat
• 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

While freshwater mussels require a host fish for metamorphosis, the host for the spike is unknown.

• Ecosystem Impact
• parasite parasite

Economic Importance for Humans: Positive

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

Economic Importance for Humans: Negative

There are no significant negative impacts of mussels on humans.

Conservation Status

Epioblasma sulcata is a federally Endangered species in both the United States and Canada. IUCN lists this species as Critically Endangered.

Other Comments

The population in Michigan is actually a subspecies population, Epioblasma obliquata perobliqua . Another subspecies, Epioblasma obliquata obliquata has a purple nacre and does not occur in Michigan.

Epioblasma obliquata is synonomous with Epioblasma sulcata . The genus Epioblasma is synonomous with Dysnomia and Plagiola .

Additional Links

Encyclopedia of Life

Contributors

Renee Sherman Mulcrone (author).

References

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Brusca, R., G. Brusca. 2003. Invertebrates . Sunderland, Massachusetts: Sinauer Associates, Inc..

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

Carman, S. 2001. Special Animal Abstract for Epioblasma obliquata perobliqua (white catspaw) . Lansing, MI: Michigan Natural Features Inventory. Accessed October 04, 2005 at http://web4.msue.msu.edu/mnfi/abstracts/aquatics/Epioblasma_obliquata_perobliqua.pdf .

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 .

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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.

Strayer, D. 1979. Some recent collections of mussels from southeastern Michigan. Malacological Revies , 12: 93-95.

Strayer, D. 1980. The freshwater mussels (Bivalvia: Unionidae) of the Clinton River, Michigan, with comments on man's impact on the fauna, 1970-1978. Nautilus , 94: 142-149.

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.