• Category
  • Length Range
    4-38 µm
  • Width Range
    3.5-6.5 µm
  • Striae in 10 µm
  • Synonyms
    Fragilaria leptostauron var. dubia (Grunow) Hust.



Valves are heavily silicified, lanceolate in larger specimens and elliptical in smaller specimens, 3.5-6.5 µm wide by 4-38 µm long. Valves demonstrate rostrate ends in larger specimens becoming rounded in smaller valves. Valve face flat, or slightly undulate due to raised costae. The valve face/mantle junction forms a sharp angle. The abvalvar edge of the mantle is parallel to the valve face/mantle junction. In girdle view, frustules are rectangular and form ribbon-like colonies, probably joined by linking spines. The colonies are attached to the substratum at one end by a frustule attached by a mucilage pad, or colonies may be planktonic. The axial area is lanceolate. The striae are distinct, composed of lineolae gradually decreasing in size from the valve face/mantle edge to both the central sternum and the valve mantle, 6-10 in 10 µm. The lineolae bear finely branched volae. Lineolae are long forming wide striae that have the appearance of punch holes on the valve. Striae vary from parallel in the central area to radiate toward the valve ends. Striae extend deeply into the valve mantle. Costae are wider than the striae. The spines are reduced to solid prominences, two on each costa, between the striae. Striae are present along the valve face edge, except at the apices. Well-developed, ocellulimbus type, apical pore fields with round poroids are present. Apical pore fields are located on the valve mantle. Rimoportula are absent. Scab-like structures, or blisters, are absent. Copulae, or girdle bands are open and do not bear perforations. Valvocopula are wider than other girdle elements and bear developed fimbriae (finger-like projections).


Frustules attach to substrates by mucilage pads; ribbon-like colonies are common.

Original Description

  • Basionym
    Fragilaria harrisonii var. dubia
  • Author
    Grunow 1862

Original Images

Staurosirella Leptoatauron Var Dubia Iconotype
Staurosirella Leptoatauron Var Dubia  Original Description

Cite This Page

Morales, E. (2010). Staurosirella leptostauron var. dubia. In Diatoms of North America. Retrieved May 30, 2024, from https://diatoms.org/species/staurosirella_leptostauron_var._dubia


The 15 response plots show an environmental variable (x axis) against the relative abundance (y axis) of Staurosirella leptostauron var. dubia 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.