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Diatoms of the United States is now known as Diatoms of North America.
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Epithemia argus

(Ehrenb.) Kütz. 1844      Category: Epithemioid
BASIONYM: Eunotia argus Ehrenb. 1843

Epithemia adnata


Epithemia reicheltii

LM scalebar = 10 µm = 40 pixels.


Contributor: Drew Meyers - June 2014
Length Range: 36-84 µm
Width Range: 8.4-13.9 µm
Striae in 10 µm: 10-11


Valves are dorsiventral, with a convex dorsal margin and a slightly concave to nearly straight ventral margin. Valve apices are rounded. At mid valve, the raphe canal curves strongly toward the dorsal margin, so that the proximal raphe is positioned at, or above 2/3 of the width. The rest of the raphe canal is positioned on the ventral margin to the apices, except in larger specimens, where the distal raphe slightly curves toward the dorsal side. The areolae are coarse, with 4-6 striae between each costa. Costae number 1-4 in 10 µm.

Original Description

Basionym: Eunotia argus
Author: Ehrenb. 1843
Length Range: µm
Striae in 10 µm:

Original Description

Original Images

Cite This Page:
Meyers, D. (2014). Epithemia argus. In Diatoms of the United States. Retrieved May 26, 2018, from

Species: Epithemia argus

Contributor: Drew Meyers

Reviewer: Rex Lowe


Krammer, K. and Lange-Bertalot, H. (1988). Bacillariophyceae. 2. Teil: Bacillariaceae, Epithemiaceae, Surirellaceae. In: Ettl, H., J. Gerloff, H. Heynig and D. Mollenhauer (eds.) Susswasserflora von Mitteleuropa, Band 2/2. Gustav Fisher Verlag, Jena.

Kützing, F.T. (1844). Die kieselschaligen Bacillarien oder Diatomeen. Nordhausen. 152 pp., 30 pls.

Patrick, R.M. and Reimer, C.W. (1975). The Diatoms of the United States, exclusive of Alaska and Hawaii, V. 2. Monographs of the Academy of Natural Sciences of Philadelphia 13.

Links & ID's

Index Nominum Algarum (INA)

Original INA

California Academy of Sciences (CAS)

Epithemia argus CAS

NCBI Genbank Taxonomy

Epithemia argus NCBI

North American Diatom Ecological Database (NADED)

NADED ID: 32005

Autecology Discussion

As in other species of Epithemia, E. argus may contain nitrogen-fixing endosymbiotic cyanobacteria. The endosymbionts enable the cells to become abundant in areas of low nitrogen concentrations. Epithemia argus was observed in a sample taken from a squeeze of moss at the edge of a small pool in Silver Lake Fen, Dickinson County, Iowa. This species tolerates high-alkaline, nutrient poor conditions.


Live Epithemia argus with intracellular spherical lipids, but endosymbiotic cyanobacteria are not evident. Collected from moss on the edge of a pool in Silver Lake Fen, DIckinison County, IA.

Credit/Source: Image by Drew Meyers

EMAP Assessment

The Environmental Protection Agency (EPA) western Environmental Monitoring and Assessment Program (EMAP) study was completed during the years 2000-2004 (see citations at bottom of this page). Over 1200 streams and rivers in 12 western states (Arizona, California, Colorado, Idaho, Montana, Nevada, North Dakota, Oregon, South Dakota, Utah, Washington and Wyoming) were selected for sampling based on a stratified randomized design. This type of design insures that ecological resources are sampled in proportion to their actual geographical presence. Stratified randomized design also allows for estimates of stream length with a known confidence in several “condition classes” (good or least-disturbed, intermediately-disturbed, and poor or most-disturbed) for biotic condition, chemistry and habitat.

EMAP Distribution

Epithemia argus

EMAP Response Plots

Epithemia argus

EMAP citations

Results are published in:

Johnson, T., Hermann, K., Spaulding, S., Beyea, B., Theel, C., Sada, R., Bollman, W., Bowman, J., Larsen, A., Vining, K., Ostermiller, J., Petersen, D. Hargett, E. and Zumberge, J. (2009). An ecological assessment of USEPA Region 8 streams and rivers. U.S. Environmental Protection Agency Region 8 Report, 178 p.

Stoddard, J. L., Peck, D. V., Olsen, A. R., Larsen, D. P., Van Sickle, J., Hawkins, C. P., Hughes, R. M., Whittier, T. R., Lomnicky, G. A., Herlihy, A. T., Kaufman, P. R., Peterson, S. A., Ringold, P. L., Paulsen, S. G., and Blair, R. (2005). Environmental Monitoring and Assessment Program (EMAP) western streams and rivers statistical summary. U.S. Environmental Protection Agency Report 620/R-05/006, 1,762 p.

Stoddard, J. L., Peck, D. V., Paulsen, S. G., Van Sickle, J., Hawkins, C. P., Herlihy, A. T., Hughes, R. M., Kaufman, P. R., Larsen, D. P., Lomnicky, G. A., Olsen, A. R., Peterson, S. A., Ringold, P. L., and Whittier, T. R. (2005). An ecological assessment of western streams and rivers. U.S. Environmental Protection Agency Report 620/R-05/005, 49 p.