Summary ²

The club naiad, clubshell pearly mussel, or clubshell, scientific name Pleurobema clava, is a species of freshwater mussel, an aquatic bivalve mollusk in the family Unionidae, the river mussels.

Distribution ³

The clubshell was historically found in the Ohio, Cumberland and Tennessee River systems and Lake Erie drainages. Within these river systems it was found in the Wabash, Kanawha, Kentucky, Green, Monogahela and Alleghany Rivers. The range of P. clava has been greatly reduced.

In Michigan P. clava is restricted to the St. Joseph River (of the Maumee drainage) in Hillsdale County.

Biogeographic Regions: nearctic (Native )

Habitat ⁴

Pleurobema clava is found in streams and small rivers, in well oxygenated riffles with coarse sand and gravel and little silt. In Michigan, runs where it was found had water currents of 0.06-0.25 meters per second.

Habitat Regions: freshwater

Aquatic Biomes: rivers and streams

Iucn red list assessment ⁵

• Needs updating

Assessor/s

• 1994
  Endangered (E)
• 1990
  Indeterminate (I)
• 1988
  Indeterminate (I)
• 1986
  Indeterminate (I)

Morphology ⁶

The northern clubshell is up to 7.6 cm (3 inches) long , and is triangular and elongate in shape. The shell is usually fairly thick, and compressed to moderately inflated. The   anterior end is rounded, the posterior end bluntly pointed. The dorsal margin is curved and slanted to the posterior end and the ventral margin is straight to slightly curved.

Umbos are low, being raised only slightly above the hinge line, and are situated at or near the anteriror end. The beak sculpture has concentric ridges at the tip of the umbo, and is not always visible.

The periostracum (outer shell layer) is yellow-brown with prominent broken green rays. Older specimens tend to be more brown or black.

On the inner shell, the   left valve has two   pseudocardinal teeth, which are small, triangular, serrated and erect. The two lateral teeth are straight to slightly curved, thin, and moderately long. The right valve has one large, erect triangular serrated pseudocardinal tooth and one lateral tooth that is also straight to slightly curved, thin and moderately long.

The beak cavity is shallow to moderately deep. The nacre is white and iridescent at the posterior end.

In Michigan, this species can be confused with the ellipse or the Wabash pigtoe. The ellipse is more compressed and has a more broadly rounded anterior end. The Wabash pigtoe lacks green rays and is also not as wedge-shaped as the clubshell.

Range length: 7.6 (high) cm.

Other Physical Features: ectothermic ; heterothermic ; bilateral symmetry

Sexual Dimorphism: sexes alike

Sources and Credits

1. (c) USFWS Endangered Species, some rights reserved (CC BY), https://www.flickr.com/photos/usfwsendsp/5098970721/
2. Adapted by rkkessler from a work by (c) Wikipedia, some rights reserved (CC BY-SA), http://en.wikipedia.org/wiki/Pleurobema_clava
3. (c) The Regents of the University of Michigan and its licensors, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/31416650
4. (c) The Regents of the University of Michigan and its licensors, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/31416651
5. (c) International Union for Conservation of Nature and Natural Resources, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/34659673
6. (c) The Regents of the University of Michigan and its licensors, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/31416652

More Info

• iNat taxon page
• Animal Diversity Web
• Biodiversity Heritage Library
• BOLD Systems BIN search
• Global Biodiversity Information Facility (GBIF)
• NatureServe Explorer 2.0
• SeaLifeBase
• World Register of Marine Species

Range Map

(c) Discover Life and original sources, some rights reserved (CC-BY-NC-SA)

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