Sellaphora alastos

(M.H.Hohn and Hellerman) Lange-Bert. and Metzeltin 1996      Category: Symmetrical biraphid
BASIONYM: Navicula americana var. alastos M.H.Hohn and Hellerman 1963

Scoliopleura peisonis


Sellaphora americana

LM scalebar = 10 µm = 40 pixels.


Contributor: Loren Bahls - March 2014
Length Range: 41-82 µm
Width Range: 11.0-17.0 µm
Striae in 10 µm: 17-19 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 narrow conopeum. The conopea are continuous through the central area, where they expand laterally. Near the valve apex, the conopea are somewhat inflated before they terminate in a point. The central area is wide and transversely rectangular. The central nodule, defined by the inner margins of the conopea, is small, elliptic, and somewhat asymmetric. 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. Striae surrounding the central area are parallel, straight, shorter, and more widely spaced than more distal striae, which are curved and radiate.

Original Description

Basionym: Navicula americana var. alastos
Author: M.H.Hohn and Hellerman 1963
Length Range: 56.7 µm
Width Range: 12.5 µm
Striae in 10 µm: 12 at valve center, 16 near the apices

Original Description

Original Images

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

Species: Sellaphora alastos

Contributor: Loren Bahls

Reviewer: Sarah Spaulding


Hohn, M.H. and Hellerman, J. (1963). The taxonomy and structure of diatom populations from three Eastern North American rivers using three sampling methods. Transactions of the American Microscopical Society 82(3):250-329.

Lange-Bertalot, H. and Metzeltin, D. (1996). Indicators of oligotrophy - 800 taxa representative of three ecologically distinct lake types, Carbonate buffered - Oligodystrophic - Weakly buffered soft water. Lange-Bertalot, H. (ed.), Iconographia Diatomologica. Annotated Diatom Micrographs. Vol. 2. Ecology, Diversity, Taxonomy. Koeltz Scientific Books. Königstein, Germany, 2:390 pp.

Links & ID's

Index Nominum Algarum (INA)

Original INA

California Academy of Sciences (CAS)

Sellaphora alastos CAS

North American Diatom Ecological Database (NADED)


Autecology Discussion

Specimens of S. alastos pictured and described on this page were collected from five ponds and small lakes in the Rocky Mountains of Montana and Colorado and the North Cascade Mountains of Washington. pH ranged from 6.73 to 6.98 and specific conductance measured 22 to 71 µS/cm. Sellaphora alastos was described from a river in eastern Canada (Hohn and Hellerman 1963) and also reported from an oligo-dystrophic lake in Finland (Lange-Bertalot and Metzeltin 1996).


Lake Caroline, Chelan County, Washington: home of Sellaphora alastos.

Credit/Source: Ryan Davis, Adventurers and Scientists for Conservation