• Category
  • Length Range
    25-150 µm
  • Width Range
    5-12 µm
  • Striae in 10 µm



Valves are bent and constricted at the center ventral margin so that the valve face is asymmetric to the apical axis. Specimens vary from highly arched to nearly straight, in smaller valves. Apices are small, strongly protracted in larger specimens, and slightly reflexed toward the dorsal margin. Frustules in girdle view are rectangular and slightly bent in the center. The raphe is excentric and located within a canal. Cells occur with the raphe on the same side on both valves. The central nodule is distinct and rectangular. Striae are indistinctly punctate, nearly parallel to radiate and may become curved toward the apices. In some specimens, two striae are aligned per fibula. Fibulae are unequally spaced along the length of the valve, with 6-10 fibulae in 10 µm.

Krammer and Lange-Bertalot (1991, p. 128) describe much finer striae for this taxon, which have not been seen in specimens from North America.

As indicated by Krammer and Lange-Bertalot (1988), the identity of this commonly reported species is uncertain. The Ehrenberg (1843) images of this species show a species clearly asymmetric to the
apical axis.


This species has been reported, sometimes in relatively large numbers, from streams and rivers in North America, but these reports have not been verified. Larger populations of this taxon reside in soil and other aerophilous habitats.

Hantzschia amphioxys live
Credit: Sylvia Lee
Living cell from soil in a puddle made by a rain storm
Hantzschia amphioxys soil sample 20190530
Credit: Sylvia Lee
Active soil biofilms on the campus of Iowa Lakeside Lab

Original Description

Eunotia amphioxys, anguste linearis dorso leviter conver laevi, ventre leviter concavo subtiliter striato, apicibus subito attenuatis. Icon!

  • Basionym
    Eunotia amphioxys
  • Author
    Ehrenb. 1843

Original Images

Hantzschia amphioxys orig illus
Hantzschia amphioxys orig desc

Cite This Page

Kociolek, P., Polaskey, M., Lee, S. (2015). Hantzschia amphioxys. In Diatoms of North America. Retrieved July 13, 2024, from https://diatoms.org/species/hantzschia_amphioxys


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