• Category
  • Length Range
    32-53 µm
  • Width Range
    8.0-10.6 µm
  • Striae in 10 µm
  • Synonyms
    Sellaphora bacilliformis (Grunow) Mereschk. 1902



Valves are linear with slightly bowed margins. Apices are broadly rounded with small polar bars visible. Raphe branches are filiform, with a broad curve halfway between the center and end of the valve. Proximal raphe ends are inflated and unilaterally bent to the primary valve side. Terminal raphe fissures are initially deflected in a small question mark shape to the primary side, but then sharply curve to the secondary side on the mantle. The conopeum is small and located within a narrow, linear axial area that becomes expanded near the central area. The conopeum appears as narrow grooves running alongside the raphe and visible as faint lines under LM. The central area is laterally expanded and rectangular to weakly bow-tie shaped. The central area is bordered by 3-4 shortened stria of similar lengths. Striae are slightly curved and reflexed and are parallel at the valve center becoming slightly radiate at the apices. Areolae very fine, and not discernible in LM.

Sellaphora laevissima is part of a species group, or complex, that has not be adequately characterized (Mann et al. 2008).

The type material of Navicula laevissima contains many species of Sellaphora and it is uncertain as to which specimen corresponds to the holotype (Mann 1989). A lectotype was designated from Kützing material housed at the British Museum (Schoeman and Archibald 1976-1980, Lange-Bertalot et al. 2003).


Sellaphora laevissima is widely distributed in rivers of North America (Reavie and Smol 1998). It has been illustrated from lakes of New England (Camburn and Charles 2000), Quebec and Labrador (Fallu et al. 2000), mid-Atlantic states (Siver et al. 2005, Siver and Hamilton 2011) and British Columbia (Cumming et al. 1995). This taxon has been collected from lake sediments (Fallu et al. 2000) and growing in the epilithon of streams (Camburn et al. 1978). It has been reported from neutral to slightly acidic waters (Camburn and Charles 2000, Siver et al. 2005), lakes with an average dissolved organic carbon concentration of 6.54 mg/L (Fallu et al. 2000) and lakes with an average total phosphorus concentration from 9.6 to 18.8 µg/L (Camburn and Charles 2000, Siver and Hamilton 2011).

Selaevissima  Continental
Credit: USGS/Biodata
The distribution of Sellaphora laevissima in rivers of the continental United States, accessed on 29 June, 2017.
Selaevissima  Alaska
Credit: USGS/Biodata
The distribution of Sellaphora laevissima in rivers of Alaska, accessed on 29 June, 2017.

Original Description

N. laevissima, vitrea, clara, bacilares, medio leviter ventricosa, apicibus late rotundas. Longit. 1/45'''. Fossil I'm Bergmehl von San Fiore.

  • Basionym
    Navicula laevissima
  • Author
    Kütz. 1844

Original Images

Nalaevissima Original Image2
Nalaevissima Original Text

Citations & Links



Cite This Page

Burge, D, and Edlund, M. (2017). Sellaphora laevissima. In Diatoms of North America. Retrieved August 18, 2018, from https://diatoms.org/species/sellaphora_laevissima


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