Valves are broadly lanceolate and somewhat dorsiventral, with subrostrate ends. The axial area is three to four times wider than the raphe. It widens gradually into the central area, which is round to elliptical and one-third to one-half as wide as the valve. The axial and central areas are ornamented with faint spots that are about the same size as areolae, but irregularly arranged. The raphe is broadly lateral, becoming reverse-lateral near the proximal ends and narrower near the distal ends. The distal ends are comma-shaped and deflected toward the dorsal side. The proximal raphe ends terminate in bulbous pores, which lie at the edge of a dark and elliptical central nodule. Striae are radiate throughout and distinctly punctate. Areolae are very coarse and number 10-14 in 10 µm.


Cymbopleura crassipunctata has been found in a small pond in western Montana. Here pH measured 7.57 and specific conductance was 16 µS/cm. The type locality for Cymbopleura crassipunctata is Savona on Kamloops Lake, British Columbia, where the species is reported to occur as a fossil (Krammer 2003). Kulikovskiy et al. (2010) recently reported this taxon from Mongolia.

Skinner  Pond 2 Photo 2 1
Credit: Loren Bahls
Skinner Pond #2, Beaverhead County, Montana: home of Cymbopleura crassipunctata.

Original Description

Valves slightly dorsiventral, broadly lanceolate, dorsal and ventral margins tapering to subrostrate ends. Length 94-127 µm, breadth 29-36 µm, maximum length/breadth ratio 3.9. Axial area moderately wide, almost in the median line of the valve. Central area large, 1/3-1/2 the valve breadth, rounded to elliptical, sometimes asymmetrical and then more well-developed dorsally or ventrally. Raphe broadly lateral, narrowing towards the distal ends, appearing reverse-lateral near the proximal ends. Proximal raphe ends bulbous central pores; terminal fissures comma-shaped and dorsally deflected. Striae radiate throughout, very distinctly punctate-lineate. Striae in the middle portion (dorsal) 6.5-9/10 µm, up to 14/10 µm towards the ends, puncta 10-14/10 µm.

  • Author
    Krammer 2003
  • Length Range
    94-127 µm
  • Width
    29-36 µm
  • Striae in 10µm
    6.5-9.0 (middle) - 14 (ends)

Original Images

Cymbopleura crassipunctata orig illus
Cymbopleura crassipunctata orig illus 3
Cymbopleura crassipunctata orig descr

Cite This Page

Bahls, L. (2011). Cymbopleura crassipunctata. In Diatoms of North America. Retrieved July 23, 2018, from


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