• Category
  • Length Range
    20.1-52.1 µm
  • Width Range
    8.7-11.6 µm
  • Striae in 10 µm



Valves are weakly arcuate, with rounded ends. Both ventral and dorsal margins are distinctly sinuate, with undulations occurring 2 in 10 µm. Undulation of the central margin is bilateral, while more dorsal and ventral undulations toward the apices are alternate. Breadth in the center of valve is 8.7-11.6 µm at undulations (widest part), 6.3-8.0 µm between undulations (narrow parts), and 3.7-5.4 µm at the ends. Striae are interrupted by a sternum near the ventral margin. Areolae are visible in LM, numbering 21-27 in 10 µm. The raphe is short and curves onto the ventral mantle, near the apices.

While many authors continue to use the name Amphicampa eruca, Brightwell (1859) elevated A. eruca Ehrenberg 1954 from Ehrenburg’s subdivision of Eunotia, Amphicampa, to the genus level Eunotia eruca. Two years later A. eruca was superfluously synonymized with A. miriabilis Ehrenberg ex Ralfs in Pritchard 1861. Furthermore, Boyer (1927) lectotypified A. eruca for the genus Amphicampa, which was later re-lectotypified to A. mirabilis (Farr et al. 1979). Here we recognize the current valid name of this taxon as Eunotia eruca (Ehrenberg) Brightwell 1859, however there is not a consensus on recognition of the genus Amphicampa (as Amphicampa, Patrick and Reimer 1966, Kociolek 2000; as Eunotia, Krammer and Lange-Bertalot 1991; and awaiting detailed analysis, Round et al. 1990, Williams and Reid 2006). The few taxa recognized in the genus have a reduced raphe system and a sinuate ventral valve margin. Further work should be conducted to treat this species, as the classification in the Eunotiophycidae is in flux.


Amphicampa eruca was originally described from a fossil deposit in Mexico (Ehrenberg 1854). Modern collections are found in disparate localities including the San Joaquin River in California (Elmore 1921 [as Eunotia eruca, Patrick and Reimer 1966 [as A. mirabilis], Kociolek 2000), and subfossil deposits in prairie potholes (Collins 1968, M. Julius, unpublished).

Eueruca  Biodata
Credit: USGS BioData
Distribution in rivers of the continental U.S. based on the National Water Quality Assessment program. Retrieved 26 July 2016.

Original Description

  • Basionym
    Amphicampa eruca
  • Author
    Ehrenb. 1854

Original Images

Amphicampa eruca orig illus
Amphicampa eruca orig descr

Citations & Links



  • Index Nominum Algarum
  • North American Diatom Ecological Database
    NADED ID: 33188

Cite This Page

Burge, D., Edlund, M. (2015). Eunotia eruca. In Diatoms of North America. Retrieved May 18, 2024, from https://diatoms.org/species/amphicampa_eruca


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