• Category
  • Length Range
    31-58 µm
  • Width Range
    7.3-10.2 µm
  • Striae in 10 µm
    15-16 at the valve center, 18-20 near the apices
  • Synonyms
    Cymbella incerta (Grunow) Cleve 1894
  • Reported As
    Cymbella incerta (Krammer and Lange-Bertalot 1986, p. 329, figs 136: 1-12)



Valves are lanceolate and moderately dorsiventral with rounded apices. Except for the largest valves, where dorsal and ventral margins are equally arched, the dorsal margin is much more strongly arched than the ventral margin. In small specimens, the ventral margin may be flat, or even slightly concave. The axial area is narrow, widening gradually toward the ellliptic central area, which is from 1/3 to 1/2 the width of the valve. The axial and central areas form a narrow longitudinal lanceolate space that is displaced somewhat to the ventral side of the apical axis. The raphe is lateral, becoming reverse-lateral near the central valve. The proximal ends are slightly inflated and deflected toward the ventral side. The distal raphe fissures are narrow and hooked toward the dorsal side. Striae are slightly radiate, becoming more strongly radiate near the apices. Areolae in the striae number 28-32 in 10 µm.


Cymbopleura incerta has been collected from Johnson Lake in southwestern Montana (photo below). Johnson Lake is at an elevation of 2329 m in the Anaconda Mountain Range. Here, on the collection date, pH measured 8.2 and specific conductance measured 140 µS/cm. In Europe, Krammer (2003) reports this species from oligotrophic habitats with low to moderate conductivity in northern and alpine regions.

26  George  Wuerthner
Credit: George Wuerthner
Johnson Lake, Anaconda-Pintler Wilderness, Deerlodge National Forest, southwestern Montana: home of Cymbopleura incerta.

Original Description

  • Basionym
    Cymbella pisciculus var. incerta
  • Author
    Grunow 1878

EMAP Assessment

EMAP Distribution

Cymbella Incerta   Grunow   Cleve 40
Map 40

Response Plots

Cymbella Incerta   Grunow   Cleve

Cite This Page

Bahls, L. (2013). Cymbopleura incerta. In Diatoms of North America. Retrieved July 18, 2019, from https://diatoms.org/species/cymbopleura_incerta


The 15 response plots show an environmental variable (x axis) against the relative abundance (y axis) of Cymbopleura incerta from all the stream reaches where it was present. Note that the relative abundance scale is the same on each plot. Explanation of each environmental variable and units are as follows:

ELEVATION = stream reach elevation (meters)
STRAHLER = distribution plot of the Strahler Stream Order
SLOPE = stream reach gradient (degrees)
W1_HALL = an index that is a measure of streamside (riparian) human activity that ranges from 0 - 10, with a value of 0 indicating of minimal disturbance to a value of 10 indicating severe disturbance.
PHSTVL = pH measured in a sealed syringe sample (pH units)
log_COND = log concentration of specific conductivity (µS/cm)
log_PTL = log concentration of total phosphorus (µg/L)
log_NO3 = log concentration of nitrate (µeq/L)
log_DOC = log concentration of dissolved organic carbon (mg/L)
log_SIO2 = log concentration of silicon (mg/L)
log_NA = log concentration of sodium (µeq/L)
log_HCO3 = log concentration of the bicarbonate ion (µeq/L)
EMBED = percent of the stream substrate that is embedded by sand and fine sediment
log_TURBIDITY = log of turbidity, a measure of cloudiness of water, in nephelometric turbidity units (NTU).
DISTOT = an index of total human disturbance in the watershed that ranges from 1 - 100, with a value of 0 indicating of minimal disturbance to a value of 100 indicating severe disturbance.