• Category
  • Length Range
    30.3-85.1 µm
  • Width Range
    9.4-13.3 µm
  • Striae in 10 µm
  • Synonyms
    Epithemia proboscidea W.Sm. 1853
    Cystopleura smithii (Carruth.) Kuntze 1891



Valves are dorsiventral with subrostrate and recurved apices in smaller specimens. The largest valves have straight and broadly rounded apices. The dorsal margin is convex and the ventral margin is strongly concave in the largest valves to weakly concave in the smallest ones. Branches of the raphe canal begin at the mid-point of the dorsal margin and proceed ventrally and distally in a broad arc to become flush with the ventral margin and then upturned slightly at the apices. Costae are 3-6 in 10 μm, with 2-5 striae between costae.


The specimens of E. smithii shown on this web page are from three lakes in southwestern Canada and northwestern Montana. One of these lakes (Wolverine Lake, photo below) had a pH of 8.83 and a specific conductance of 107 µS/cm at the time of collection. Krammer and Lange-Bertalot (1988) report this taxon as widespread in northern Europe, often as an epiphyte, in mesotrophic to eutrophic ponds, lakes and rivers with low to medium electrolyte content. Patrick and Reimer (1975) report E. smithii from Lake Michigan.

Upper  Wolverine  Lake 2
Credit: Loren Bahls
Wolverine Lake (upper), Kootenai National Forest, Lincoln County, Montana: home of Epithemia smithii

Original Description

  • Author
    Carruth. 1864

Cite This Page

Bahls, L. (2024). Epithemia smithii. In Diatoms of North America. Retrieved June 23, 2024, from https://diatoms.org/species/epithemia_smithii


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