• Category
  • Length Range
    19.8-31.8 µm
  • Width Range
    6.4-8.7 µm
  • Striae in 10 µm
    12-16 at center valve, up to 18 at the ends
  • Reported As
    Cymbella amphicephala (Patrick and Reimer 1975, plate 4, fig. 11)
    Cymbella amphicephala (Krammer and Lange-Bertalot 1986, fig. 142: 3-14)
    Cymbella amphicephala (A. Schmidt et al. 1875, fig. 9: 64)



Valves are elliptic and slightly dorsiventral with the curvature of the dorsal and ventral sides very similar. Apices are capitate to subcapitate and bent slightly towards the ventral margin. The axial area is narrow and located near the midline of the valve. The central area is very small and asymmetric, formed by 1-3 short striae on one or both sides. The raphe is filiform with proximal ends deflected slightly towards the ventral margin. Proximal raphe ends are not expanded. Distal raphe ends are deflected dorsally. Striae are slightly radiate throughout and more closely spaced towards the apices. Areolae are difficult to resolve in LM and number 32-35 in 10 µm.


Cymbopleura amphicephala is widely distributed in small headwater lakes and streams throughout the Northwest United States, primarily in mountain regions but also in plains streams. Here it prefers well oxygenated and alkaline (calcium-bicarbonate) waters with moderate electrical conductance (see table below). It is rarely found in abundance. Patrick and Reimer (1975) report it as widespread in the United States "frequently under conditions of high oxygen content and at a pH above 7". Cymbopleura naviculiformis also prefers well oxygenated waters, but waters with circumneutral pH and much lower concentrations of dissolved solids (Montana Diatom Database).

Cymboamphi Chem 001
Credit: Montana Diatom Database
Abundance-weighted means of selected water quality variables measured concurrently with the collection of samples containing Cymbopleura amphicephala.

Original Description

  • Basionym
    Cymbella amphicephala
  • Author
    Naegeli ex Kütz. 1849

Original Images

Cymbella amphicephala orig descr


Jun 13, 2024 - Change in species circumscription

When first opened, the page for Cymbopleura amphicephala on this website was presented in a broad sense. That is, it included images and measurements for C. amphicephala, C. frequens and C. similiformis. These three taxa are are now considered to be unique biological species. As of this update, the taxonomic circumscription was reduced so that now only images and measurements of C. amphicephala sensu stricto are presented. - S. Spaulding and L. Bahls

Cite This Page

Bahls, L. (2012). Cymbopleura amphicephala. In Diatoms of North America. Retrieved June 13, 2024, from https://diatoms.org/species/cymbopleura_amphicephala


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