• Category
  • Length Range
    10-40 µm
  • Width Range
    3-5 µm
  • Striae in 10 µm
    10-13 in the center, 14-16 at the footpole



Valves are linear-clavate, with a squarish to rounded, protracted headpole. The footpole is rounded. The axial area is narrow, and expanded to form a transverse fascia as a central area. Striae are shortened on either side of the central area. A single, distinct stigma is present near the proximal raphe ends. The raphe is weakly lateral and slightly undulate. The external proximal ends are slightly dilated and rounded. Striae are radiate, near the center, becoming more strongly radiate at the footpole.

Under SEM, G. pygmaeum has C-shaped areolae and a round, unoccluded opening of the stigma. The proximal fissures of the raphe are dilated, while the distal raphe ends are deflected onto the mantle. The apical porefield is bisected by the raphe and formed by round, unoccluded porelli that are separated from the areolae by a hyaline area.


Gomphonema pygmaeum was described from rock scrapes from the shore of Lake Superior. The specimens illustrated here are from Oregon, and it likely occurs in other regions of the country.

Original Description

  • Author
    Kociolek and Stoermer 1991
  • Length Range
    11-40 µm
  • Width
    3-5 µm
  • Striae in 10µm

Original Images

G Pygmaeum Origillus
G Pygmaeum2 Orig Des

Cite This Page

Kociolek, P. (2015). Gomphonema pygmaeum. In Diatoms of North America. Retrieved July 13, 2024, from https://diatoms.org/species/gomphonema_pygmaeum


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