• Category
  • Length Range
    75.9-120.9 µm
  • Width Range
    17.0-20.1 µm
  • Striae in 10 µm
    6-9 at the valve center, up to 15 near the apices
  • Reported As
    Cymbella cymbiformis (Patrick and Reimer 1975, Pl 10, Fig 3 [not Fig 4])



Valves are lanceolate and dorsiventral with bluntly rounded apices. The dorsal margin is moderately arched; the ventral margin is weakly concave with a slightly gibbous middle. The axial area is linear. The central area is small and elliptic, somewhat wider on the ventral side. The raphe is distinctly lateral, becoming reverse-lateral near the proximal ends. Proximal raphe ends are deflected ventrally and terminate with inflated pores. Terminal raphe fissures are deflected ventrally at about 45 degrees. Striae are widely spaced and nearly parallel at the valve center, becoming radiate near the apices. Areolae are distinct in LM and widely spaced, numbering 14-17 in 10 µm. Stigmata are variable in number. Usually there are 1 or 2 on the ventral side of the central nodule.

Note that the width of the specimens illustrated here not conform with the width of European C. cymbiformis (Krammer 2002). Further work may show this North American taxon to be a different species.


The specimens of C. cymbiformis shown on this web page were collected from Lake Winona, a shallow lake with abundant submerged and emergent vegetation on the west side of Glacier National Park, Montana. At the time of collection, Lake Winona had a pH of 7.20 and electrical conductance of 250 µS/cm. Krammer (2002) reports this species as widely distributed in arctic, subarctic, and temperate regions, primarily in the littoral zones of oligotrophic lakes and streams with low to very low electrolyte content.

Credit: Billy Schweiger, National Park Service
Closeup of Lake Winona shoreline, Glacier National Park, Montana: home of Cymbella cymbiformis
P9230531 1
Credit: Billy Schweiger, National Park Service.
Lake Winona, Glacier National Park, Montana.

Original Description

  • Author
    C.Agardh 1830

Original Images

Cymbella cymbiformis orig descr

Cite This Page

Bahls, L. (2016). Cymbella cymbiformis. In Diatoms of North America. Retrieved April 14, 2024, from https://diatoms.org/species/cymbella_cymbiformis


The 15 response plots show an environmental variable (x axis) against the relative abundance (y axis) of Cymbella cymbiformis 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.