• Category
  • Length Range
    63.0-97.0 µm
  • Width Range
    15.0-16.5 µm
  • Striae in 10 µm
    23-25 in the center, 25-26 at the ends



Valves are linear-lanceolate-rhomboid. The apices are broadly rounded apices and slightly constricted. Across most of the valve, striae are parallel or sometimes slightly radiate. Striae are very slightly convergent at the apices. Striae are radiate at the apices. In the longitudinal direction, the areolae are partially organized giving the longitudinal striae a wavy appearance. Areolae are generally unorganized at the center of the valve and minimal amount of organization is present near the apices. Externally, the openings of the areolae are lanceolate in shape. Internally, the areolae are oval and occluded by hymenes. The raphe branches curve slightly and are enclosed by longitudinal ribs. A very robust and slightly curved porte-crayon is present where the longitudinal ribs and long, linear helictoglossa fuse. The central nodule is elongate and fuses with the longitudinal ribs, which appear to be interrupted at the central area, rather than constricted. External raphe ends are slightly dilated and accompanied by a small, round depression. The central area may have 0-4 isolated poroids. An isolated poroid may also be present near the distal raphe ends.

Original Description

  • Basionym
    Navicula rhomboides var. amphipleuroides
  • Author
    Grunow 1880

Original Images

Navicula rhomboides var. amphipleuroides orig illus
Navicula rhomboides var. amphipleuroides orig illus

Cite This Page

Kociolek, P., Graeff, C. (2011). Frustulia amphipleuroides. In Diatoms of North America. Retrieved May 18, 2024, from https://diatoms.org/species/frustulia_amphipleuroides


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