• Category
  • Length Range
    45-166 µm
  • Width Range
    13.5-17 µm
  • Striae in 10 µm



Valves are dorsiventral and are 45-166 μm long and 13.5 to 17 μm wide. Valves taper toward rounded to rostrate to slightly capitate ends. Striae are 8-10 in 10 μm and costae are 4-5 in 10 μm. There are 2-3 striae between costae. The dorsal margin is strongly convex and the ventral margin is slightly concave. The raphe canal lies against the ventral margin at distal ends of the valve and arches toward the dorsal margin in the valve center. The central arch of the canal is approximately 7-8 μm above the ventral margin reaching almost half the distance to the dorsal margin.


Similar to other species of Epithemia, E. turgida contains nitrogen-fixing cyanobacteria. The endosymbionts enable cells to become abundant in microhabitats with a low N/P ratio. It is frequently abundant as an epiphyte on Cladophora and other coarse filamentous algae, particularly in western rivers.

Epithemia turgida Iho41070 1Ed 1
Credit: R.L. Lowe
A large post-initial valve, at 165 µm.
Epithemia turgida 005 1
Credit: R.L. Lowe
Epithemia turgida (larger cells) and E. sorex (smaller cells) epiphytic on Cladophora from the Eel River, California.
Epithemia turgida 006
Credit: R.L. Lowe
Live Epithemia turgida showing endosymbiotic cyanobacteria.

Original Description

  • Basionym
    Navicula turgida
  • Author
    Ehrenb. 1832
  • Length Range
    45-225 µm

Original Images

Orig Descr1

Cite This Page

Lowe, R. (2010). Epithemia turgida. In Diatoms of North America. Retrieved June 23, 2024, from https://diatoms.org/species/epithemia_turgida


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