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Diatoms of the United States is now known as Diatoms of North America.
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Distrionella incognita

(E.Reichardt) D.M.Williams 1990      Category: Araphid
BASIONYM: Fragilaria incognita E.Reichardt 1988

REPORTED AS: Fragilaria incognita emend. (Morales, Bahls & Cody 2005) 

Discostella stelligera


Ellerbeckia arenaria

LM scalebar = 10 µm = 80 pixels.


Contributor: Loren Bahls - March 2012
Length Range: 28-76 µm
Width Range: 1.9-2.9 µm
Striae in 10 µm: 20-26


Valves are lightly silicified, linear, and very narrow with capitate apices. The central sternum is barely visible in LM. Transapical costae are irregularly spaced and number 11-17 in 10 µm. Striae are faint and also irregularly spaced.

Original Description

Basionym: Fragilaria incognita
Author: E.Reichardt 1988
Length Range: 50-85 µm
Width Range: 1.8-3.0 µm
Striae in 10 µm: 22-28

Original Description

Schalen schmal lanzettlich bis linear-lanzettlich mit schwach bis mäβig kopfig gerundeten Enden, 50-85 µm lang, 1,8-3 µm breit. Transapikalstreifen sehr zart und unregelmäβig gestellt, 22-28 in 10 µm. Im LM fallen nur die unregelmäβig breiten Zwischenräume zwischen den Areolen reihan auf. Axialarea sehr eng und im LM kaum erkennbar, Zentralarea fehlt. In der Nähe eines Schalenpols befinder sich ein Lippenfortsatz.

Original Images

Cite This Page:
Bahls, L. (2012). Distrionella incognita. In Diatoms of the United States. Retrieved May 27, 2018, from

Species: Distrionella incognita

Contributor: Loren Bahls

Reviewer: Sarah Spaulding


Morales, E.A., Bahls, L.L. and Cody, W.R. (2005). Morphological studies of Distrionella incognita (Reichardt) Williams (Bacillariophyceae) from North America with comments on the taxonomy of Distrionella Williams. Diatom Research 20: 115–135.

Reichardt, E. (1988). Neue Diatomeen aus Beyerischen und Nordtiroler Alpenseen. Diatom Research 3(2): 237-244.

Williams, D.M. (1990). Distrionella D.M. Williams, nov. gen., a new araphid diatom (Bacillariophyta) genus closely related to Diatoma Bory. Archiv für Protistenkunde 138: 171-177.

Links & ID's

Index Nominum Algarum (INA)

Transfer INA

California Academy of Sciences (CAS)

Distrionella incognita CAS

North American Diatom Ecological Database (NADED)


Autecology Discussion

Cells of Distrionella incognita may be solitary or form stellate, zig-zag, or ribbon-like colonies. It has two long flat plastids, one on either side of a central nucleus. It is benthic, but may appear incidentally in the plankton. In the United States its range is largely limited to the Canadian Rockies (“Crown of The Continent”) ecoregion in northwestern Montana and to rivers (e.g. Kootenai River in northern Idaho) whose headwaters are in this ecoregion. Here it is found in lakes and streams with alkaline pH (range 7.3-8.6) and moderate levels of electrolytes (specific conductance range 222-616 µS/cm).


Stellate colony of Distrionella incognita from Birch Creek, Pondera County, Montana.

Credit/Source: Loren Bahls