• Category
  • Length Range
    18.8-47.7 µm
  • Width Range
    2.2-3.0 µm
  • Striae in 10 µm



Valves are linear-lanceolate with narrow, acutely rounded apices. Fibulae on the eccentric keel number 11-15 in 10 µm. On most valves the two median fibulae are more widely spaced, giving the appearance of a "central nodule". Striae are parallel and composed of indistinct areolae.

This taxon is very similar to and may be conspecific with Nitzschia radicula Hustedt.


The specimens pictured on this web page are from streams on the Northwestern Great Plains of Montana and from the Weiser River in northern Idaho. Krammer & Lange-Bertalot (1988) report this species from electrolyte-rich to brackish waters. It was originally described from a lake in Turkey and also reported from the North Sea Coast of Belgium. Nitzschia radicula is very similar to N. incognita, both in morphology and autecology.

Original Description

  • Author
    Legler and Krasske 1940
  • Length Range
    34-52 µm
  • Width
    2 µm
  • Striae in 10µm

Original Images

Nitzschia Incognita Origimag001
Nitzschia Incognita Origimag002
Nitzschia Incognita Origidesc001

Cite This Page

Bahls, L. (2016). Nitzschia incognita. In Diatoms of North America. Retrieved July 21, 2018, from https://diatoms.org/species/nitzschia_incognita


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