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Diatoms of the United States is now known as Diatoms of North America.
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Sellaphora americana

(Ehrenb.) D.G.Mann 1989      Category: Symmetrical biraphid
BASIONYM: Navicula americana Ehrenb. 1843

REPORTED AS: Navicula americana (Patrick and Reimer 1966, p. 493, pl. 47, fig. 3) | Navicula americana (Krammer and Lange-Bertalot 1986, p. 188, fig. 67: 1) 

Sellaphora alastos


Sellaphora atomoides

LM scalebar = 10 µm = 40 pixels.


Contributor: Loren Bahls - March 2014
Length Range: 58-93 µm
Width Range: 14.6-19.1 µm
Striae in 10 µm: 16-18 midway between valve center and apex


Valves are broadly linear, with parallel or weakly concave margins. Apices are obtusely rounded. The axial area is narrow and undulate, bordered on each side by a wide conopeum. The conopea are continuous through the central area, where they expand laterally. The conopea narrow to a point near the apices. The central area is wide and rounded. The central nodule, defined by the inner margins of the conopea, is small and elliptic. The raphe is filiform and follows the undulate margins of adjacent conopea. Proximal raphe ends are deflected slightly to one side and tipped with small pores. Distal raphe ends are comma-shaped. Central striae are straight, parallel, and shorter, but with about the same spacing as more distal striae, which are curved and radiate.

Original Description

Basionym: Navicula americana
Author: Ehrenb. 1843
Length Range: µm
Striae in 10 µm:

Original Description

Original Images

Cite This Page:
Bahls, L. (2014). Sellaphora americana. In Diatoms of the United States. Retrieved May 26, 2018, from

Species: Sellaphora americana

Contributor: Loren Bahls

Reviewer: Sarah Spaulding


Ehrenberg, C.G. (1843). Verbreitung und Einfluß des mikroskopischen Lebens in Süd- und Nord-Amerika. Abhandlungen der Königlichen Akademie der Wissenschaften zu Berlin, 1841: 291-445, 4 Tafel.

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.

Mann, D.G. (1989). The diatom genus Sellaphora: Separation from Navicula. British Phycological Journal 24: 1-20.

Patrick, R.M. and Reimer, C.W. (1966). The Diatoms of the United States exclusive of Alaska and Hawaii, V. 1. Monographs of the Academy of Natural Sciences of Philadelphia 13.

Links & ID's

Index Nominum Algarum (INA)

Original INA

California Academy of Sciences (CAS)

Sellaphora americana CAS

North American Diatom Ecological Database (NADED)

NADED ID: 170008

Autecology Discussion

Specimens of S. americana pictured and described on this web page were collected from a pond near Helena, Montana, a pond in Lincoln County, Montana and from Denton Slough, a backwater bay of Lake Pend Oreille in Bonner County, northern Idaho. The Montana ponds have pH values of 6.0 and 6.9, and specific conductance values of 37 and 50 µS/cm. Denton Slough has a pH of 7.3 and specific conductance of 150 µS/cm. Krammer and Lange-Bertalot (1986) report this species as cosmopolitan in standing waters. Patrick and Reimer (1966) report it as widely distributed in U. S. waters with circumneutral pH.

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

Sellaphora americana

EMAP Response Plots

Sellaphora americana

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.