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Eunotia triodon

Ehrenb. 1837      Category: Eunotioid

Eunotia trinacria


Eunotia zasuminensis

LM scalebar = 10 µm = 40 pixels.


Contributor: Loren Bahls - July 2012
Length Range: 47-74 µm
Width Range: 15-23 µm
Striae in 10 µm: 15-18 near valve center, 19-21 near the ends


Valves are moderately arched. The dorsal margin has three broadly rounded undulations, with the number of undulations consistent across large to small valves. The ventral margin is concave and follows the same curvature as the dorsal margin. The apices are protracted, broadly rounded and more narrow than the undulations. Distal raphe ends are curved toward the dorsal margin close to the valve ends. Striae are radiate throughout and are of two types: 1) complete striae that extend the width of the valve and 2) short striae that are interspersed between complete striae along the dorsal margin. A fine hyaline line is near and parallel to the ventral margin. Striae on either side of this line may be aligned or displaced. Areolae in the striae number 27-30 in 10 µm.

Original Description

Author: Ehrenb. 1837
Length Range: µm
Striae in 10 µm:

Original Description

Original Images

Cite This Page:
Bahls, L. (2012). Eunotia triodon. In Diatoms of the United States. Retrieved May 22, 2018, from

Species: Eunotia triodon

Contributor: Loren Bahls

Reviewer: Paula Furey


Ehrenberg, C.G. (1837). Über ein aus fossilen Infusorien bestehendes, 1832 zu Brod verbacknes Bergmehl von der Grenzen Lapplands in Schweden. Bericht über die zur Bekanntmachung geeigneten Verhandlungen der Königlich-Preussischen Akademie der Wissenschaften zu Berlin 1837:43-45.

Krammer, K. and Lange-Bertalot, H. (1991). Bacillariophyceae. 3. Teil: Centrales, Fragilariaceae, Eunotiaceae. In Ettl, H., Gerloff, J., Heynig, H. & Mollenhauer, D. (Eds.). Süsswasserflora von Mitteleuropa. 2(3): 1-576. Gustav Fisher Verlag, Stuttgart, Germany.

Lange-Bertalot, H., Bak, M., Witkowski, A. and Tagliaventi, N. (2011). Eunotia and some related genera. Diatoms of the European Inland Waters and Comparable Habitats. 6: 747 pp.

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)

Eunotia triodon CAS

North American Diatom Ecological Database (NADED)

NADED ID: 33063

Autecology Discussion

Eunotia triodon is uncommon in the Northern Rockies and North Cascades. The specimens shown here are from Blodgett Lake in the Bitterroot Mountains of western Montana and Cutthroat Lake in northern Washington (photos below). Blodgett Lake is at an elevation of 3,000 m. Here pH measured 6.50 and specific conductance was 7 µS/cm.


Blodgett Lake, Selway-Bitterroot Wilderness, Bitterroot National Forest, Montana: home of Eunotia triodon.

Credit/Source: R. A. Carlsen

Adventurers and Scientists for Conservation volunteer Ryan Davis collecting Eunotia triodon at Cutthroat Lake, Washington, July 2013.

Credit/Source: Ryan Davis