• Category
  • Length Range
    9.1-51.1 µm
  • Width Range
    2.9-5.5 µm
  • Striae in 10 µm
  • Synonyms
    Neofragilaria bicapitata (A.Mayer) D.M.Williams and Round



Valves are linear to lanceolate with rostrate apices. Striae are irregularly spaced and do not align from opposite sides of the valve where they meet at the central sternum. The striae appear relatively thick, but areolae not visible in LM. Large apical porefields are present at both ends of the valve. Length to breadth ratio decreases with increasing valve length. In SEM, the striae are seen to be uniseriate. Two rimoportulae are present, one at each apex of the valve. Each rimoportula is aligned with the striae. Small marginal spines are present on each interstria. Spines continue around the valve apex, and are positioned on the apical porefields.

Original Description

  • Basionym
    Fragilaria bicapitata
  • Author
    A.Mayer 1917
  • Length Range
    17-32 µm
  • Striae in 10µm

Original Images

Fragilaria bicapitata orig illus
F Bicapitata Text

Cite This Page

Bishop, I. (2014). Fragilariforma bicapitata. In Diatoms of North America. Retrieved May 20, 2024, from https://diatoms.org/species/fragilariforma_bicapitata


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