Eunotia perpusilla

(Grunow) Berg 1939      Category: Eunotioid
BASIONYM: Eunotia tridentula var. perpusilla Grunow 1881

REPORTED AS: Eunotia paratridentula (Kulikovsky and Lange-Bertalot 2011, pg. 33, Pl. 19, Fig. 1-9, Pl. 37, Fig. 3-6 ) | Eunotia perpusilla var. perpusilla (Patrick 1958, pg. 7, Pl. 1, Fig. 7) 

Eunotia pectinalis


Eunotia rhomboidea

LM scalebar = 10 µm = 80 pixels.


Contributor: Ian Bishop - January 2017
Length Range: 14-20 µm
Width Range: 3.2-4.2 µm
Striae in 10 µm: 16-20


Valves are dorsiventral. The ventral margin is concave, with two subapical swellings. The dorsal margin is convex and undulate, with the number of undulations varying with valve size (typically 3-4). Striae are radiate, evenly spaced, with occasional shortened striae intruding from the dorsal margin. Apices are protracted, capitate and weakly recurved. Terminal raphe ends are distinct in LM and positioned near the ventral margin.

Additional nomenclatural observations

In Van Heurck’s Atlas (1880-1881), a drawing with the caption “E. tridentula Ehr. var.? perpusilla Grun.” was published. In the “Table Alphabetique” (the accompanying text for the Atlas plates), which was published in 1884, Van Heurck changes his mind and drops the “var.? perpusilla”, leaving “E. tridentula Ehr.” and still referring to the same figure in the Atlas (Pl. XXXIV, Fig. 31).

In 1939, A. Berg elevated E. tridentula var. perpusilla to the rank of species, resulting in Eunotia perpusilla (Grunow) Berg. While he did not specifically include the text “stat. nov.”, at the time this was not required of him and the omission does not invalidate his transfer.

It is the author’s opinion that E. muscicola var. tridentula Nörpel & Lange-Bertalot 1993 (and its current form Eunotia paratridentula Lange-Bertalot & Kulikovsky 2011) is conspecific with E. perpusilla (Grunow) Berg, as illustrated in Van Heurck’s Atlas.

It should be noted that Lange-Bertalot has a separate interpretation of the identity of E. perpusilla. He believes that E. perpusilla (referring to its basionym E. tridentula var. perpusilla) is synonymous with E. microcephala Krasske ex Hustedt 1932, and we believe this to be incorrect (Lange-Bertalot et al. 2011). Lange-Bertalot and Nörpel also considered Eunotia perpusilla Grunow sensu Patrick 1958 to be conspecific with E. muscicola var. tridentula (Krammer and Lange-Bertalot 1991). Lastly, it should also be noted that Patrick referred to North American specimens, such a those above, as E. perpusilla. Unfortunately, she attributed the incorrect authority, using Grunow, instead of (Grunow) Berg (Patrick 1958).

Original Description

Basionym: Eunotia tridentula var. perpusilla
Author: Grunow 1881
Length Range: µm
Striae in 10 µm:

Original Description

Original Images

Cite This Page:
Bishop, I. (2017). Eunotia perpusilla. In Diatoms of the United States. Retrieved March 25, 2017, from

Species: Eunotia perpusilla

Contributor: Ian Bishop

Reviewer: Marina Potapova


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.

Kulikovskiy, M.S., Lange-Bertalot, H., Witkowski, A., Dorofeyuk, N.I. and Genkal, S.I. (2010). Diatom assemblages from Sphagnum bogs of the world. I. Nur bog in northern Mongolia. Bibliotheca Diatomologica 55: 1-326.

Lange-Bertalot, H. (1993). 85 Neue taxa und uber 100 weitere neu definierte Taxa erganzend zur Subwasserflora von Mittleuropa. Bibliotheca Diatomologica 27, 454 p. Cramer, Berlin, Stuttgart.

Patrick, R.M. (1958). Some nomenclatural problems and a new species and a new variety in the genus Eunotia (Bacillariophyceae). Notulae Naturae 312: 1-15.

Van Heurck, H. (1881). Synopsis des Diatomées de Belgique. Atlas. Ducaju & Cie., Anvers. pls 31-77.

Van Heurck, H. (1885). Synopsis des Diatomées de Belgique. Texte. Martin Brouwers & Co., Anvers. p. 157. (description).

Links & ID's

Index Nominum Algarum (INA)

Original INA

California Academy of Sciences (CAS)

Eunotia perpusilla CAS

North American Diatom Ecological Database (NADED)


Autecology Discussion

This taxon is frequently found in the temperate holoarctic (Kulikovsky et al. 2011). In recent USGS NAWQA surveys, E. perpusilla has been confirmed in the Pacific Northwest (Puget Sound basin and Willamette Valley) and across the eastern US, from western Maine to northern Georgia. Patrick (1958; 1966) found it in western Montana (Missoula and Ravalli counties). Although broadly distributed, relatively few valves are reported in these North American localities.