• Category
  • Length Range
    70-86 µm
  • Width Range
    24-28 µm
  • Striae in 10 µm
    8-10 (dorsal) and 9-11 (ventral) at the valve center; 13-15 (dorsal) and 14-16 (ventral) at the apices
  • Reported As
    Cymbella cuspidata (Patrick and Reimer 1975, plate 6, fig. 2)



Valves are broadly elliptic and slightly dorsiventral, with strongly arched dorsal and ventral margins. The ventral margin tapers toward short and somewhat ventrally deflected apiculate apices. The length to width ratio is 2.9-3.3. The narrow axial area widens gradually from the apices toward a large, rounded and asymmetric central area. The raphe is lateral and narrows toward the distal and proximal ends. Proximal raphe ends are deflected ventrally and shaped like a crochet hook or a crosier. Terminal raphe fissures are deflected dorsally. Striae are radiate throughout and more closely spaced towards the apices. Areolae are easily resolved in LM and number 18-24 in 10 µm.


Cymbopleura apiculata has been recorded infrequently in small ponds and fens in the Northern Rockies, where it is associated with organic substrates and abundant aquatic vegetation. In one of these habitats (Cut Bank Pond, Glacier National Park), pH measured 7.77 and specific conductance measured 53 µS/cm. In another (Skinner Pond #1, Beaverhead County, Montana), pH measured 7.82 and specific conductance measured 49 µS/cm.

Akokala  Fen  Gnp
Credit: E. William Schweiger, National Park Service.
Akokala Fen, Glacier National Park, Montana: home of Cymbopleura apiculata.
Sofa  Wetland  A 2
Credit: Barb Johnston, Parks Canada.
Sofa Mountain Wetland A, Waterton Lakes National Park, Alberta: home of Cymbopleura apiculata.

Original Description

Valves not or only very slightly dorsiventral, broadly subelliptical to elliptical-lanceolate, dorsal and ventral margins strongly arched, tapering abruptly to apiculate-cuspidate ends. Length 45-113 µm, breadth 22-27 µm, maximum length/breadth ratio 3.5. Axial area moderately narrow, almost in the median line of the valve. Central area distinctly set off, about 1/3 the valve breadth, roundish or slightly elliptical, sometimes asymmetrical. Raphe lateral, narrowing towards the distal and proximal ends. Proximal raphe ends slightly ventrally tipped (Fig. 7:8) or crochet-hooked (Fig. 11:1); terminal fissures dorsally deflected (Fig. 7:9). Striae radiate throughout, distinctly punctate (Fig. 7:8, 10). Striae in the middle portion (dorsal) 8-10/10 µm, 12-15/10 µm towards the ends, puncta 18-23/10 µm.

  • Author
    Krammer 2003
  • Length Range
    45-113 µm
  • Width
    22-27 µm
  • Striae in 10µm
    8-10 at valve center (dorsal); 12-15 towards the apices

Original Images

Cymbopleura apiculata orig illus
Cymbopleura apiculata orig illus 2
Cymbopleura apiculata orig illus 3
Cymbopleura apiculata orig descr

Cite This Page

Bahls, L. (2012). Cymbopleura apiculata. In Diatoms of North America. Retrieved May 29, 2024, from https://diatoms.org/species/cymbopleura_apiculata


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