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Cymbopleura incerta

(Grunow) Krammer 2003      Category: Asymmetrical biraphid
BASIONYM: Cymbella pisciculus var. incerta Grunow 1878
SYNONYM(S): Cymbella incerta (Grunow) Cleve 1894 
REPORTED AS: Cymbella incerta (Krammer and Lange-Bertalot 1986, p. 329, figs 136: 1-12) 

Cymbopleura inaequalis


Cymbopleura incertiformis

LM scalebar = 10 µm = 80 pixels.


Contributor: Loren Bahls - April 2013
Length Range: 31-58 µm
Width Range: 7.3-10.2 µm
Striae in 10 µm: 15-16 at the valve center, 18-20 near the apices


Valves are lanceolate and moderately dorsiventral with rounded apices. Except for the largest valves, where dorsal and ventral margins are equally arched, the dorsal margin is much more strongly arched than the ventral margin. In small specimens, the ventral margin may be flat, or even slightly concave. The axial area is narrow, widening gradually toward the ellliptic central area, which is from 1/3 to 1/2 the width of the valve. The axial and central areas form a narrow longitudinal lanceolate space that is displaced somewhat to the ventral side of the apical axis. The raphe is lateral, becoming reverse-lateral near the central valve. The proximal ends are slightly inflated and deflected toward the ventral side. The distal raphe fissures are narrow and hooked toward the dorsal side. Striae are slightly radiate, becoming more strongly radiate near the apices. Areolae in the striae number 28-32 in 10 µm.

Original Description

Basionym: Cymbella pisciculus var. incerta
Author: Grunow 1878
Length Range: µm
Striae in 10 µm:

Original Description

Original Images

Cite This Page:
Bahls, L. (2013). Cymbopleura incerta. In Diatoms of the United States. Retrieved May 20, 2018, from

Species: Cymbopleura incerta

Contributor: Loren Bahls

Reviewer: Rex Lowe


Cleve, P.T. (1894). Synopsis of the Naviculoid Diatoms, Part I. Kongliga Svenska-Vetenskaps Akademiens Handlingar 26(2):1-194, 5 pls.

Cleve, P.T. and Möller, J.D. (1878). Collection of 324 diatom slides with accompanying analyses of A. Grunow. Parts 1-6 (1877-1882), Upsala.

Krammer, K. (2003). Cymbopleura, Delicata, Navicymbula, Gomphocymbellopsis, Afrocymbella. Diatoms of Europe. Diatoms of the European Inland Waters and Comparable Habitats 4: 1-530.

Krammer, K. and Lange-Bertalot, H. (1986). Bacillariophyceae. 1. Teil: Naviculaceae. In: Ettl, H., J. Gerloff, H. Heynig and D. Mollenhauer (eds.) Süsswasserflora von Mitteleuropa, Band 2/1. Gustav Fisher Verlag, Jena. 876 pp.

Links & ID's

Index Nominum Algarum (INA)

Original INA
Transfer INA

California Academy of Sciences (CAS)

Cymbopleura incerta CAS

NCBI Genbank Taxonomy

Cymbella incerta NCBI

North American Diatom Ecological Database (NADED)

NADED ID: 23101

Autecology Discussion

Cymbopleura incerta has been collected from Johnson Lake in southwestern Montana (photo below). Johnson Lake is at an elevation of 2329 m in the Anaconda Mountain Range. Here, on the collection date, pH measured 8.2 and specific conductance measured 140 µS/cm. In Europe, Krammer (2003) reports this species from oligotrophic habitats with low to moderate conductivity in northern and alpine regions.


Johnson Lake, Anaconda-Pintler Wilderness, Deerlodge National Forest, southwestern Montana: home of Cymbopleura incerta.

Credit/Source: George Wuerthner

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

Cymbopleura incerta

EMAP Response Plots

Cymbopleura incerta

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.