Cymbopleura incertiformis

Krammer 2003      Category: Asymmetrical biraphid

Cymbopleura incerta


Cymbopleura incertiformis var. laterostrata

LM scalebar = 10 µm = 80 pixels.


Contributor: Loren Bahls - January 2014
Length Range: 30-61 µm
Width Range: 7.0-9.4 µm
Striae in 10 µm: 14-17 at the valve center, 20-24 at the ends on the dorsal side


Valves are lanceolate and not, or just barely, dorsiventral. Apices are either not protracted, or they are weakly protracted and subrostrate. The narrow axial area widens somewhat near the valve center. The central area is rounded and more or less symmetric, formed by shallow depressions on the dorsal and ventral sides. The raphe is lateral, becoming filiform toward the ends. Proximal raphe ends are deflected ventrally and terminate with weakly expanded pores. Distal raphe ends are hooked toward the dorsal side. Striae are radiate throughout and more widely spaced near the valve center. Areolae are difficult to resolve in LM and number 28-32 in 10 µm.

Original Description

Author: Krammer 2003
Length Range: 24-60 µm
Width Range: 6.5-8.5 µm
Striae in 10 µm: 15-19 at the valve center, up to 20 towards the apices on the dorsal side

Original Description

Original Images

Cite This Page:
Bahls, L. (2014). Cymbopleura incertiformis. In Diatoms of the United States. Retrieved April 24, 2018, from

Species: Cymbopleura incertiformis

Contributor: Loren Bahls

Reviewer: Diane Winter


Krammer, K. (2003). Cymbopleura, Delicata, Navicymbula, Gomphocymbellopsis, Afrocymbella. Diatoms of Europe. Diatoms of the European Inland Waters and Comparable Habitats 4: 1-530.

Links & ID's

Index Nominum Algarum (INA)

Original INA

California Academy of Sciences (CAS)

Cymbopleura incertiformis CAS

North American Diatom Ecological Database (NADED)


Autecology Discussion

Cymbopleura incertiformis is widespread and locally abundant in lakes and ponds of the northern Rocky Mountains and North Cascades. In lakes with water quality data, pH ranged from 6.7 to 7.8 and specific conductance ranged from 10 to 53 µS/cm. Krammer (2003) reports variety incertiformis as “widely distributed in the subarctic, nordic, and alpine area in oligotrophic to dystrophic habitats with commonly low electrolyte content, sometimes in large numbers”.


Goat Flats Tarn, Snohomish County, Washington: home of Cymbopleura incertiformis.

Credit/Source: Craig Weiland, Adventurers and Scientists for Conservation.