Cymbopleura subaequalis

(Grunow) Krammer 2003      Category: Asymmetrical biraphid
BASIONYM: Cymbella subaequalis Grunow in Van Heurck 1880

REPORTED AS: Cymbella subaequalis (Patrick and Reimer 1975, p. 24, plate 3, figs. 13-14) 

Cymbopleura rupicola


Cymbopleura subcuspidata

LM scalebar = 10 µm = 80 pixels.


Contributor: Loren Bahls - August 2012
Length Range: 23-47 µm
Width Range: 7.1-9.4 µm
Striae in 10 µm: 12-16 at the valve center, 16-20 near the ends


Valves are lanceolate to elliptic-lanceolate and somewhat dorsiventral. The dorsal and ventral margins are arched and taper to obtusely rounded, subtly protracted apices. The axial area is narrow and widens gradually from the apices toward the central area. The central area is small and irregular, barely wider than the axial area. The raphe is lateral and narrows toward the proximal and distal ends. Proximal raphe ends are deflected ventrally and slightly expanded. Distal raphe fissures are semicircular and deflected dorsally. Striae are radiate throughout and indistinctly punctate. Areolae number 30-38 in 10 µm.

Original Description

Basionym: Cymbella subaequalis
Author: Grunow in Van Heurck 1880
Length Range: µm
Striae in 10 µm:

Original Description

Original Images

Cite This Page:
Bahls, L. (2012). Cymbopleura subaequalis. In Diatoms of the United States. Retrieved April 22, 2018, from

Species: Cymbopleura subaequalis

Contributor: Loren Bahls

Reviewer: Sarah Spaulding


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

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.

Van Heurck, H. (1880). Synopsis des Diatomées de Belgique. Atlas. Ducaju & Cie., Anvers.

Links & ID's

Index Nominum Algarum (INA)

Transfer INA

California Academy of Sciences (CAS)

Cymbopleura subaequalis CAS

North American Diatom Ecological Database (NADED)

NADED ID: 190017

Autecology Discussion

There are 45 records for C. subaequalis in the Montana Diatom Database from northwestern Montana, northern Idaho, and southwestern Alberta. The species is especially common and widespread in the Canadian Rockies (“Crown of the Continent”) Ecoregion, where it prefers cold, oligotrophic, and somewhat alkaline waters with low to moderate specific conductance. Krammer (2003) reports this species as cosmopolitan in temperate and colder regions in both the northern and southern hemispheres.


Lake Josephine, Glacier National Park, Montana: home of Cymbopleura subaequalis.

Credit/Source: Loren Bahls

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 subaequalis

EMAP Response Plots

Cymbopleura subaequalis

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.