Eunotia diadema

Ehrenb. 1837      Category: Eunotioid

REPORTED AS: Eunotia serra var. diadema (Krammer & Lange-Bertalot 1991) | Eunotia serra var. diadema (Patrick & Reimer 1966) 

Eunotia charliereimeri


Eunotia enischna

LM scalebar = 10 µm = 40 pixels.


Contributor: Loren Bahls - July 2012
Length Range: 34-65 µm
Width Range: 14-26 µm
Striae in 10 µm: 7-10 in the valve center, 12-17 near the apices


Valves are highly arched. The dorsal margin has a constant 6 bluntly pointed undulations. The ventral margin is concave and follows the same curvature as the dorsal margin. The apices are wider than the undulations and obtusely rounded. Apices are set off from (never coalesce with) the terminal undulations, even in smaller specimens. Distal raphe ends lie along the valve face very close and parallel to each end. Striae are radiate throughout and of two types: complete striae that extend the full width of the valve and short striae that occur only along the dorsal margin. Fan-shaped packets of short striae fill the gaps between complete striae within each undulation. A fine transparent line runs close and parallel to the ventral margin. Striae on either side of this line may be continuous or displaced. Areolae in the striae are easily resolved in LM and number 20-23 (mostly 22) in 10 µm.

The specific epithet diadema is the Latin word for “crown”.

Original Description

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

Original Description

Original Images

Cite This Page:
Bahls, L. (2012). Eunotia diadema. In Diatoms of the United States. Retrieved April 24, 2018, from

Species: Eunotia diadema

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 diadema CAS

North American Diatom Ecological Database (NADED)

NADED ID: 33055

Autecology Discussion

In the Montana Diatom Collection, Eunotia diadema occurs in fens, ponds and small lakes, primarily in the Idaho Batholith and Canadian Rockies ecoregions of western Montana. These waters typically have circumneutral to somewhat acidic pH and low conductivity. Patrick & Reimer (1966) combine this taxon with Eunotia tetraodon and report them as occurring in oligotrophic or dystrophic swamps and bogs in the New England states and Utah. Lange-Bertalot et al. (2011) report it as a component of the Holarctic flora where it is associated with other acidophilous diatoms.


Paradise Pond, Glacier National Park, Montana: home of Eunotia diadema.

Credit/Source: Loren Bahls