Cymbella proxima

Reimer in R.M.Patrick and Reimer 1975      Category: Asymmetrical biraphid

Cymbella perfossilis


Cymbella proxima fo. gravida

LM scalebar = 10 µm = 40 pixels.


Contributor: Marina Potapova - March 2012
Length Range: 51-104 µm
Width Range: 17.8-23.0 µm
Striae in 10 µm: 7-8 in the center valve, up to 12 at the ends


Valves are strongly dorsiventral with acuminate rounded apices. The dorsal margin is strongly arched, whereas the ventral margin is slightly concave, but with a tumid central portion. The central area is circular and about one third of the valve width in diameter, somewhat smaller in shorter valves. Two to five stigmata are arranged in a line in the ventral side of the central area. The axial area is narrow and almost central. The raphe is lateral near the middle of the valve, becoming filiform near the distal and proximal ends. The outer and inner raphe slits usually do not appear to cross, but sometimes the proximal and distal raphe ends can be seen as very slightly reverse-lateral. The proximal raphe ends have bulbous central ends that curve to the ventral margin. The terminal raphe fissures are dorsally deflected nearly 90º. Apical pore fields are present at both apices. Striae are radiate. The external openings of areolae are apically oriented slits. Areolae number 14-16 in 10 µm.

Original Description

Author: Reimer in R.M.Patrick and Reimer 1975
Length Range: 45-120 µm
Width Range: 18-24 µm
Striae in 10 µm: 7-8 in the center valve, approximately 11 at the ends

Original Description

Original Images

Cite This Page:
Potapova, M. (2012). Cymbella proxima. In Diatoms of the United States. Retrieved April 26, 2018, from

Species: Cymbella proxima

Contributor: Marina Potapova

Reviewer: Sarah Spaulding


Krammer, K. (2002). The genus Cymbella. Diatoms of Europe. Diatoms of the European Inland Waters and Comparable Habitats 3: 1-584.

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)

Cymbella proxima CAS

NCBI Genbank Taxonomy

Cymbella proxima NCBI

North American Diatom Ecological Database (NADED)

NADED ID: 23071

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

Cymbella proxima

EMAP Response Plots

Cymbella proxima

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.