• Category
  • Length Range
    58.3-93.4 µm
  • Width Range
    14.6-19.1 µm
  • Striae in 10 µm
    16-18 midway between valve center and apex
  • Reported As
    Navicula americana (Patrick and Reimer 1966, p. 493, pl. 47, fig. 3)
    Navicula americana (Krammer and Lange-Bertalot 1986, p. 188, fig. 67: 1)



Valves are broadly linear, with parallel or weakly concave margins. Apices are obtusely rounded. The axial area is narrow and undulate, bordered on each side by a wide conopeum. The conopea are continuous through the central area, where they expand laterally. The conopea narrow to a point near the apices. The central area is wide and rounded. The central nodule, defined by the inner margins of the conopea, is small and elliptic. The raphe is filiform and follows the undulate margins of adjacent conopea. Proximal raphe ends are deflected slightly to one side and tipped with small pores. Distal raphe ends are comma-shaped. Central striae are straight, parallel, and shorter, but with about the same spacing as more distal striae, which are curved and radiate.


Specimens of S. americana pictured and described on this web page were collected from a pond near Helena, Montana, a pond in Lincoln County, Montana and from Denton Slough, a backwater bay of Lake Pend Oreille in Bonner County, northern Idaho. The Montana ponds have pH values of 6.0 and 6.9, and specific conductance values of 37 and 50 µS/cm. Denton Slough has a pH of 7.3 and specific conductance of 150 µS/cm. Krammer and Lange-Bertalot (1986) report this species as cosmopolitan in standing waters. Patrick and Reimer (1966) report it as widely distributed in U. S. waters with circumneutral pH.

Original Description

  • Basionym
    Navicula americana
  • Author
    Ehrenb. 1843

EMAP Assessment

EMAP Distribution

Sellaphora Americana   Ehrenberg   Mann 20
Map 20

Response Plots

Sellaphora Americana   Ehrenberg   Mann

Cite This Page

Bahls, L. (2014). Sellaphora americana. In Diatoms of North America. Retrieved August 20, 2018, from https://diatoms.org/species/sellaphora_americana


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