• Category
  • Length Range
    9-15.3 µm
  • Width Range
    6.9-10.6 µm
  • Striae in 10 µm
    rapheless: 10-14, raphe: 25-27 at margin, 38-40 near axial area



Valves are broadly elliptical. The raphe valve has a narrow axial area, although the striae near the axial area may not be visible in LM. The striae are fine and radiate. The striae on the raphe valve number 25 to 27 in 10 µm near the valve margin, and near 40 in µm near the axial area. The rapheless valve has a broad, lanceolate axial area that covers 1/3 to 1/2 the width of the valve. The striae are coarse, square to elliptical, and radiate. The number of areolae ranges from 3 to 5.


This species has been reported from northern Europe, Canada and New England, USA. It is probably most common in lotic ecosystems.

Original Description

  • Author
    E.Reichardt 1982
  • Length Range
    11.5-13.5 µm
  • Width
    8.5-9.5 µm

Original Images

Cocconeis pseudothumensis orig illus
Cocconeis pseudothumensis orig descr

Cite This Page

Lowe, R. (2015). Cocconeis pseudothumensis. In Diatoms of North America. Retrieved February 24, 2024, from https://diatoms.org/species/cocconeis_pseudothumensis


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