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.

Eucocconeis flexella

(Kütz.) F.Meister 1912      Category: Monoraphid
BASIONYM: Cymbella flexella Kütz. 1844
SYNONYM(S): Achnanthes flexella (Kütz.) Brun 

Eucocconeis americana


Eucocconeis laevis

LM scalebar = 10 µm = 40 pixels.


Contributor: Marina Potapova - October 2010
Length Range: 18-40 µm
Width Range: 9-20 µm
Striae in 10 µm: 22-24 in center valve


Frustules are strongly bent in girdle view with concave raphe valve and convex rapheless valve. Valves are elliptical-lanceolate with slightly drawn-out ends and deep mantles. Valve face has depressions along the margins. The raphe valve has a narrow axial area and a lanceolate-rhomboid central area. The raphe is straight or slightly sigmoid with terminal ends sharply turned to opposite directions. Rapheless valve has a narrow linear or slightly sigmoid axial area and a large rectangular or hexagonal central area. The striae are punctate, strongly radiate on raphe valve and slightly radiate on rapheless valve, 22-24 in 10 μm.

Original Description

Basionym: Cymbella flexella
Author: Kütz. 1844
Length Range: 41 µm
Striae in 10 µm:

Original Description

CYMBELLA? FLEXELLA. Taf. 4. Fig. XIV, Taf. 6. Fig. VIII. (420/1). C. laevissima, mi¬nor, a latere secundario elliptica, subsigmoidea, apicibus parum productis obtusis, altero latere cur-vata, (genuflexa) dorso convexo, ventre concavo exciso, apice truncato. In Quellwasser bei Thun in der Schweiz! — Länge 1/55”’.

Original Images

Cite This Page:
Potapova, M. (2010). Eucocconeis flexella. In Diatoms of the United States. Retrieved May 20, 2018, from

Species: Eucocconeis flexella

Contributor: Marina Potapova

Reviewer: Mark Edlund


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

Meister, F. (1912). Die Kieselalgen der Schweiz. Beiträge zur Kryptogamenflora der Schweiz, 4/1, 1–254.

Links & ID's

Index Nominum Algarum (INA)

Original INA

California Academy of Sciences (CAS)

Eucocconeis flexella CAS

North American Diatom Ecological Database (NADED)

NADED ID: 187001

Autecology Discussion

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

Eucocconeis flexella

EMAP Response Plots

Eucocconeis flexella

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.