• Category
  • Length Range
    63-87 µm
  • Width Range
    15-17 µm
  • Striae in 10 µm
  • Synonyms
    Navicula undula Schumann



Valves are linear and slightly triundulate in larger specimens. The central and distal undulation are of about the same width. The apices are rostrate to subcapitate, about half of the valve width. The axial area is linear-lanceolate, about one third of the valve width. The central area is large and round. Small round depressions are found on the external valve surface in the axial and central areas. The striae are radiate at center valve, becoming convergent at the apices. The raphe is lateral and almost straight, with very slightly expanded proximal ends and large semi-circular terminal fissures located in large rounded terminal areas.

The concept of Pinnularia undula presented here follows that of Krammer (2000). In contrast, the iconotype shows a slightly different valve margin, axial area, and no obvious markings. Therefore, future work may show this taxon to differ from the original description.


Pinnularia undula occurs in the benthos of lakes in the northeastern US.

Original Description

  • Basionym
    Navicula undula
  • Author
    Schumann 1862
  • Length Range
    77-95 µm

Original Images

Pinn Undula Orig Ill
Pinn Undula Orig Descr

Cite This Page

Friedman, N., Potapova, M. (2021). Pinnularia undula. In Diatoms of North America. Retrieved April 21, 2024, from https://diatoms.org/species/pinnularia-undula


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