• Category
  • Length Range
    10–40 µm
  • Width Range
    6–12 µm
  • Striae in 10 µm



Valves are elliptic-lanceolate, with rounded ends. Transapical ribs are 3-6 in 10 µm. Striae are uniseriate, consisting of small poroid areolae. The axial area is linear and very narrow. A rimoportula is present at one apex. Apical pore fields are present at both apices. Frustules are rectangular in girdle view.


This taxon is considered to be a cold water species. In western North America, it is found in streams across a range of elevation, but particularly in association with mosses. It reaches its greatest abundances in low nutrient, low conductivity waters with little human disturbance.

Original Description

  • Basionym
    Fragilaria mesodon
  • Author
    Ehrenb. 1839

EMAP Assessment

EMAP Distribution

D Mesodon 20
Map 20

Response Plots

Diatoma Mesodon


Sep 19, 2017 - Transfer from the genus Diatoma to Odontidium

Re-examination of the genera Diatoma and Odontidium led Jüttner et al. (2015) to recommend the use of the name Odontidium at the generic level for taxa treated from that sub-genus of Diatoma. Refer to Jüttner et al. for an account, including a neotype designation for O. hyemale and commentary on the nomenclatural priority of Odontidium.

This taxon appeared as Diatoma mesodon Kützing 1844 in the Diatoms of the US flora from May 2010 through September 2017. As of September 2017, the taxon appears as Odontidium mesodon (Ehrenberg) Kützing 1844.

Cite This Page

Potapova, M. (2009). Odontidium mesodon. In Diatoms of North America. Retrieved July 16, 2018, from https://diatoms.org/species/odontidium_mesodon


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