• Category
  • Length Range
    5.4-13 µm
  • Width Range
    2.4-3.3 µm
  • Striae in 10 µm
  • Synonyms
    Nitzschia frustulum var. inconspicua (Grunow) Grunow 1882
    Homoeocladia inconspicua (Grunow) Kuntze 1898



Valves are lanceolate to linear-lanceolate, usually with wedge-shaped apices. Large specimens have linear-lanceolate valves with protracted and narrowed apices, while small specimens are lanceolate or sometimes elliptical. At the smaller end of the size range, the apices may be rounded.

Striae are uniseriate, evenly distributed, mostly parallel, and radiate at the apices. Areolae are simple round pores plainly discernible with LM. Fibulae are small, somewhat rectangular, and evenly distributed, except for a central gap. Fibulae number 12-14 in 10 µm.

With SEM, it can be observed that the striae extend to the raphe canal. the raphe canal is raised on a elevated keel. Proximal raphe ends are expanded, while terminal raphe ends are hooked. Internally, fibulae are biconcave, giving a roundish appearance to the interfibular spaces.


Field and culture investigations of N. inconspicua and N. soratensis suggest that the two taxa are not closely related and differ in ecological preferences (Trobajo et al. 2013). Based on Trobajo et al., N. inconspicua is euryhaline, so it has a wide tolerance of brackish to freshwater habitats. It was found in high conductivity (988 µS/cm) and alkalinity (~200 mg/L CaCO3) conditions in Spain. In contrast, N. soratensis is considered to be restricted to low specific conductance waters. In rivers of the United Kingdom, the two species were found growing together in lower salinity sites.

Laboratory-based experiments on European collections (Trobajo et al. 2013) suggest that both taxa are indifferent to phosphorus, at least in the range of 0.016-1.63 mg/L P. As a result, it appears that conductivity and/or alkalinity are the main environmental factors driving the differences between these two species in streams. Further suggestions are that these taxa are separated primarily by watershed geology rather than by anthropogenic nutrient pollution.

Original Description

  • Author
    Grunow 1862

Original Images

Nitzschia inconspicua Orig ilus
Nitzschia inconspicua Original Description

Citations & Links



Cite This Page

Garzon, E., Aycock, L., Stancheva, R. (2018). Nitzschia inconspicua. In Diatoms of North America. Retrieved July 24, 2024, from https://diatoms.org/species/nitzschia-inconspicua


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