Visit us at

Diatoms of the United States is now known as Diatoms of North America.
This site has been redesigned and updated, and will be closing soon.

Epithemia turgida

(Ehrenb.) Kütz. 1844      Category: Epithemioid
BASIONYM: Navicula turgida Ehrenb. 1832

Epithemia sorex


Eucocconeis alpestris

LM scalebar = 10 µm = 40 pixels.


Contributor: Rex Lowe - December 2010
Length Range: 45-166 µm
Width Range: 13.5-17 µm
Striae in 10 µm: 8-10


Valves are dorsiventral and are 45-166 μm long and 13.5 to 17 μm wide. Valves taper toward rounded to rostrate to slightly capitate ends. Striae are 8-10 in 10 μm and costae are 4-5 in 10 μm. There are 2-3 striae between costae. The dorsal margin is strongly convex and the ventral margin is slightly concave. The raphe canal lies against the ventral margin at distal ends of the valve and arches toward the dorsal margin in the valve center. The central arch of the canal is approximately 7-8 μm above the ventral margin reaching almost half the distance to the dorsal margin.

Original Description

Basionym: Navicula turgida
Author: Ehrenb. 1832
Length Range: 45-225 µm
Striae in 10 µm:

Original Description

Original Images

Cite This Page:
Lowe, R. (2010). Epithemia turgida. In Diatoms of the United States. Retrieved May 22, 2018, from

Species: Epithemia turgida

Contributor: Rex Lowe

Reviewer: Sarah Spaulding


DeYoe, H.R., Lowe, R.L. and Marks, J.C. . (1992). Effects of nitrogen and phosphorus on the endosymbiont load of Rhopalodia gibba and Epithemia turgida (Bacillariophyceae). Journal of Phycology 28: 723–873. 10.1111/j.0022-3646.1992.00773.x

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.

Sims, P.A. (1983). A taxonomic study of the genus Epithemia with special reference to the type species E. turgida (Ehrenb.) Kütz. Bacillaria 6: 211-235.

Links & ID's

Index Nominum Algarum (INA)

Original INA

California Academy of Sciences (CAS)

Epithemia turgida CAS

NCBI Genbank Taxonomy

Epithemia turgida NCBI

North American Diatom Ecological Database (NADED)

NADED ID: 32004

Autecology Discussion

Similar to other species of Epithemia, E. turgida contain nitrogen-fixing endosymbiotic cyanobacteria which enable this taxon to become abundant in microhabitats with a low N/P ratio. It is frequently very abundant as an epiphyte on Cladophora and other coarse filamentous algae in western rivers.


Epithemia turgida (larger cells) and E. sorex (smaller cells) epiphytic on Cladophora from the Eel River, California.

Credit/Source: R. Lowe

Live Epithemia turgida showing endosymbiotic cyanobacteria.

Credit/Source: R. Lowe

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 turgida

EMAP Response Plots

Epithemia turgida

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.