Snuffbox
Epioblasma triquetra
Summary 5
Epioblasma triquetra, common name the Snuffbox, is a species of freshwater mussel, a mollusk in the family Unionidae. It is native to eastern North America, where it is a listed as an endangered species in both Canadaand the United States.
Distribution 6
Global Range: (5000-20,000 square km (about 2000-8000 square miles)) It was historically widespread in the upper Mississippi and Ohio River drainages. It was widespread but never abundant in the Tennessee River system. It has been drastically reduced in range and is endangered in many states where it occurs. Extant populations can still be found in Wisconsin, Illinois, Indiana, Kentucky, Michigan, Ohio, Pennsylvania, Tennessee, and West Virginia. Most populations are small and geographically isolated from one another. In Mississippi, it is found only in Tennessee River drainage (Jones et al., 2005). In Arkansas, it is known from a handfull of sites represented by only single or a few specimens in each (Harris and Gordon, 1987; Harris et al., 1997). It was historically known from New York in the Niagara River, Lake, Erie, and the Buffalo River but is likely extirpated there (Strayer and Jirka, 1997) (although two spent shells were recently found in the Niagara River drainage- Marangelo and Strayer, 2000).
Habitat 7
In Michigan, Epioblasma triquetra is found in small- to medium-sized rivers, 7 to 23 m wide. In the southeastern part of Michigan, it is more common in streams between lakes. Its fish host, the logperch, Percina caprodes reproduces in both rivers and lakes, and populations of E. triquetra have been also been found in lakes. However, the invasion of the zebra mussel Dreissena polymorpha, has decimated most lake populations of the snuffbox in southeastern Michigan.
Habitat Regions: freshwater
Aquatic Biomes: rivers and streams
Habitat 8
Habitat Type: Freshwater
Comments: Found in riffles of medium and large rivers with stony or sandy bottoms, in swift currents, usually deeply buried (Baker, 1928).
Morphology 9
The snuffbox is up to 6.4 cm (2.5 inches) long , and is triangular or elongated in shape. The shell is uniformly solid, and inflated. The anterior end is rounded. Males have a truncated posterior end and females have a more expanded posterior end. The dorsal and ventral margins are straight to slightly curved. Females in general are smaller and can be distinguished from males by the ribs and teeth-like sculpture at the posterior end.
Umbos are broad and slightly raised above the hinge line. The beak sculpture is has three to four double-looped bars, although these may be worn and faint.
The periostracum (outer shell layer) is smooth, yellow to yellow-green. The shells also have dark green rays with blotches or chevron markings.
On the inner shell, the left valve has two pseudocardinal teeth, which are high, thin and triangular. The two lateral teeth are short, slightly curved, and slightly striated. The right valve has one high, triangular, thin, triangular pseudocardinal tooth. The one right lateral tooth is short, slightly curved and slightly striated.
The beak cavity is moderately to fairly deep. Although the nacre is white and iridescent at the posterior end.
In Michigan, this species can be confused with the slippershell, and deertoe. The snuffbox is generally smaller, and females are tooth-like at the posterior end. Slippershells are smaller (therefore growth lines are closer together) and lack the black blotches and chevrons. The deertoe is generally larger than the snuffbox and is more rounded in shape.
Range length: 6.4 (high) cm.
Other Physical Features: ectothermic ; heterothermic ; bilateral symmetry
Sexual Dimorphism: sexes shaped differently
Nature serve conservation status 10
Rounded Global Status Rank: G3 - Vulnerable
Reasons: This species is declining throughout its widespread range and has become increasingly rare, although several dozen occurrences remain; many of them with good viability. Distribution is greatly fragmented but remains relatively wide. Long-term viability of most populations is questionable especially those in large rivers where zebra mussel populations are now established. Degree of decline has not been established.
Intrinsic Vulnerability: Moderately vulnerable
Comments: The decline in the overall range suggests that it is not tolerant to poor water quality. The sites where it still occurs are usually high quality streams with little disturbance to the substrate or riparian zone. Sensitive to pollution, siltation, habitat perturbation, inundation, and loss of glochidial hosts.
Other Considerations: This is the most widespread member of the critically endangered genus EPIOBLASMA. It is considered as threatened by the freshwater mussel subcommittee of the endangered species committee of the American Fisheries Society (Williams et al., 1993).
Sources and Credits
- (c) Tim Lane, some rights reserved (CC BY-NC-ND), https://www.flickr.com/photos/119210184@N05/12941134324/
- (c) U.S. Fish and Wildlife Service Northeast Region, some rights reserved (CC BY), https://www.flickr.com/photos/usfwsnortheast/8002919245/
- (c) Femorale, some rights reserved (CC BY-NC), http://www.femorale.com/shellphotos/detail.asp?species=Epioblasma%20triquetra%20(Rafinesque,%201820)
- (c) Smithsonian Institution, National Museum of Natural History, Department of Invertebrate Zoology, some rights reserved (CC BY-NC-SA), https://collections.nmnh.si.edu/services/media.php?env=iz&irn=24840
- Adapted by rkkessler from a work by (c) Wikipedia, some rights reserved (CC BY-SA), http://en.wikipedia.org/wiki/Epioblasma_triquetra
- (c) NatureServe, some rights reserved (CC BY-NC), http://eol.org/data_objects/28852309
- (c) The Regents of the University of Michigan and its licensors, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/31392981
- (c) NatureServe, some rights reserved (CC BY-NC), http://eol.org/data_objects/28852316
- (c) The Regents of the University of Michigan and its licensors, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/31392982
- (c) NatureServe, some rights reserved (CC BY-NC), http://eol.org/data_objects/28852302
