• Category
  • Length Range
    200-270 µm
  • Width Range
    32.5-39 µm
  • Striae in 10 µm



Valves are linear, with a slightly swollen central valve. The apices are slightly swollen and rounded. The axial area is very slightly asymmetric about apical plane, positioned closer to the secondary valve side at the valve ends. The axial area is about one-fourth the width of the valve. The central area is elliptic, asymmetric, and wider on primary side of the valve. The striae are radiate in the valve center and convergent at the apices, where they are longer on the primary valve side than on the secondary side. The striae are crossed by two longitudinal lines corresponding to boundaries of internal alveolae openings. The raphe is lateral, complex, and the proximal raphe ends have large central pores. The terminal raphe fissures are hooked.


We documented this taxon in the ANSP Boyer Collection from Norwalk, Connecticut. It has also been recorded from two cold-water springs on the Rocky
Boy Reservation (Chippewa-Cree) in the Rocky Mountains of Montana (Bahls, personal communication).

According to Krammer (2000) this diatom is found in oligotrophic waters with low to average conductivity.

Original Description

  • Author
    Krammer 2000
  • Length Range
    176-304 µm
  • Width
    32-40 µm

Original Images

Pinnularia nobilis orig illus 2 1
Pinnularia nobilis orig illus 3 1
Pinnularia nobilis orig illus 1
Pinnularia nobilis orig desc 1

Citations & Links

Cite This Page

Kersey, M., Potapova, M. (2022). Pinnularia nobilis var. regularis. In Diatoms of North America. Retrieved May 28, 2024, from https://diatoms.org/species/pinnularia-nobilis-regularis


The 15 response plots show an environmental variable (x axis) against the relative abundance (y axis) of Pinnularia nobilis var. regularis 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.