• Category
  • Length Range
    255.0-265.0 µm
  • Width Range
    45.0 µm
  • Striae in 10 µm



Valve of Frickea lewisiana are linear-lanceolate with bluntly rounded apices. There is little relative variation in the lengths of specimens, which were 255.0-265.0 µm in length and 45.0 µm in breadth. The majority of the striae are perpendicular, but they become convergent near the apices. Striae are composed of small, round areolae. Striae density is 22-24 in 10 µm. The longitudinal ribs are complete and extend to the helictoglossa. At the central area, the ribs enclose the central nodule but do not fuse with it. Externally, both the proximal and distal raphe ends are T-shaped. The areolae on the valve face opposite the location of the helictoglossa are highly unorganized and sparse. The areolae around the relatively small, symmetrical central area are expanded transversely, several times the length of the typical areolae openings on the valve. Rows of poroids are present between the raphe and longitudinal ribs near the central area and apices.


Original Description

  • Basionym
    Navicula lewisiana
  • Author
    Grev. 1863

Original Images


Cite This Page

Graeff, C. (2010). Frickea lewisiana. In Diatoms of North America. Retrieved July 22, 2018, from https://diatoms.org/species/frickea_lewisiana


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