• Category
  • Length Range
    25.1-43.6 µm
  • Width Range
    7.1-8.4 µm
  • Striae in 10 µm
    23 – 29
  • Reported As
    Neidium affine f. hercynicum (Hustedt, F. 1930, pp. [i]-vii, [1]-466.)



Valves are narrowly elliptic, with broadly rounded apicies. The axial area is slightly diagonal and gradually tapers toward the central area and ends. Proximal raphe ends are short, deflected in opposite directions, and thinner than the middle portion of the raphe. Distal raphe ends are also thinner than the main portion of the raphe and they extend over the distal valve margin. The central area has a diagonal to diamond shape. Longitudinal canals are present on either side of the valve, usually marginal, sometimes submarginal, and are either linear or, in some specimens, concave at the apicies. In the center of the valve, the striae are distinctly oblique at an angle of 23° to 28° from the central sternum. At the apices, the striae may nearly parallel. Stria density is high and may be difficult to resolve under LM. In some specimens, Voigt discontinuities are prominent.


This taxon has been recorded from small, dystrophic streams and swamps from Connecticut and Pennsylvania (Patrick and Reimer 1966). The specimens illustrated here were found in rare abundance in association with a large population of Odontidium and Meridion in samples from a wet wall below the Upper Coney Lake, Allenspark, Colorado.

N. hercynicum sample site_1
Credit: Lane Allen
Close up image of the wet wall below the Upper Coney Lake, Allenspark, Colorado.
N. hercynicum sample site_2
Credit: Lane Allen
A wide view of the wet wall below the Upper Coney Lake, Allenspark, Colorado
Neidium hercynicum angle of striation
Credit: Ayowole Fifo
Image illustrating how the angle of striation of N. hercynicum is calculated.

Original Description

  • Author
    Mayer 1917
  • Length Range
    25-75 µm
  • Width
    5-13 µm
  • Striae in 10µm

Original Images

Neidium hercynicum original image caption
Neidium hercynicum original image
Neidium hercynicum original description

Cite This Page

Fifo, A., Allen, L. (2023). Neidium hercynicum. In Diatoms of North America. Retrieved April 16, 2024, from https://diatoms.org/species/neidium-hercynicum


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