• Category
  • Length Range
    6-21 µm
  • Width Range
    3.5-5.0 µm
  • Striae in 10 µm
  • Synonyms
    Navicula stroemii (stromii) Hust.



Valves are linear to linear-elliptic, with broadly rounded apices. Larger specimens have apices that are slightly subcapitate. The raphe is straight, with straight proximal ends. The terminal raphe fissures are long and deflected to the secondary valve side. The axial area is linear, with grooves visible under LM as parallel lines on each side of the raphe. The grooves are partially covered by non-porous conopeum. Grooves and conopea are interrupted by a small central area. Striae are slightly radiate throughout most of the valve, in some specimens nearly parallel near the apices. Areolae are small, rounded, and number approximately 70 in 10 μm. Polar bars are absent.

The size range of this species is slightly wider than in populations described from Europe (Falasco et al. 2009), which is not unusual when additional populations from various geographic areas are examined. The stria density (23-25 in 10 μm) in North American specimens is on the lower end of the range reported by Falasco et al. (2009). The areola density (70 in 10 μm) is somewhat lower than that reported (78-80 in 10 μm) in European populations.


Sellaphora stroemii is most common in hard-water streams. The images on this page are from a stream in Missouri; this taxon has also been reported from the western US (EPA EMAP Survey), southeast (Bishop et al. 2017), and California (USGS 2017).

Original Description

Navicula Strömii HUST. nov. spec. Schalen breit linear mit deutlich welligen Rändern und breit gerundeten Enden, 10-15 µ lang, 3,5-4,5 µ breit. Raphe gerade, Polspalten nach denselben Seiten abgebogen, klein. Axialarea eng, Zentralarea klein, etwas quer verbreitert. Transapikalstreifen zart, leicht radial, etwa 24 in 10 µ, in der Mitte etwas weiter gestellt (Fig. 3). Habituell der N. subhamulata var. undulata HUST. sehr ähnlich, unterscheidet sich aber durch die fehlende Kieselrippe um die Raphe und durch die viel kleineren Polspalten. Nicht selten in Nr. 1, aber infolge der geringen Größe leicht zu übersehen.

  • Basionym
    Navicula strömii
  • Author
    Hust. 1931
  • Length Range
    10-15 µm
  • Width
    3.5-4.5 µm
  • Striae in 10µm

Original Images

Sellaphora Stroemii  Orig Ill
Sellaphora Stroemii  Orig Descr

Cite This Page

Potapova, M., Shainker, S. (2021). Sellaphora stroemii. In Diatoms of North America. Retrieved December 07, 2021, from https://diatoms.org/species/sellaphora_stroemii


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