• Category
  • Length Range
    24-34.5 µm
  • Width Range
    5-6.5 µm
  • Striae in 10 µm



Valves are linear-elliptical to linear-lanceolate with narrow, rounded apices. Valves are 24.0-34.5 µm long and 5.0-6.5 µm wide. Striae are 12-17 in 10 µm. The axial area is narrow and linear and the central area is asymmetrically rounded. The raphe is filiform with enlarged proximal raphe ends that weakly unilaterally deflected. The distal raphe fissures are distinctly deflected from the valve face onto the mantle, with the deflection to the secondary side. The lineolate striae are strongly radiate at the center and radiate throughout the valve. The space between each stria is equal or wider to the width of the stria. Voigt faults are often evident on the secondary side of the valve. Areolae are 24-28 in 10 µm. A thickened central nodule is present on the primary side, positioned between the deflected proximal fissures.


This taxon is characteristic of high pH, conductivity, and nitrogen and phosphorus concentrations. It is tolerant of high amounts of sediment, turbidity, and watershed disturbance.

Original Description

Valva linearis vel lanceolata, 33 µ longa, 6µ lata, apicibus rotundatis: striis lineatis 15-17 per 10 µ, ad centrum valvae conspicue radiatis, ad margines valvae minus conspicuae radiatis; area axiali angusta; area centrali distincte rectangulare. In the general shape of the central area and the formation of the striae this species is quite similar to Navicula gracilis Ehr. and its varieties. However, it is typically smaller in size and the striae are more radiate in the center of the valve and radiate instead of convergent at the ends. Also the striae are finer (Fig. 6). Distribution-Brazil: Rio Grande do Sul, current water at roadside, near the Lagua dos Quadros, 385 H. Kleerekoper July: 1941 (A-25741). Type (A-25740), scrapings of stones in a rapid of the river Maquuine, an affluent of the Lagua dos Quadros 337 H. Kleerekoper June 1941 (A-25737).

  • Author
    R.M.Patrick 1944
  • Length Range
    33 µm
  • Width
    6 µm
  • Striae in 10µm

Original Images

Navicula Symmetrica
Nasymmetrica  Orig Descr

Cite This Page

Manoylov, K., Hamilton, P. (2010). Navicula symmetrica. In Diatoms of North America. Retrieved June 17, 2024, from https://diatoms.org/species/navicula_symmetrica


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