• Category
  • Length Range
    67-83 µm
  • Width Range
    8.30-9.30 µm
  • Striae in 10 µm



Valves are linear, with slightly triundulate sides and subcapitate apices. The axial area is about 1/3-1/2 of the valve width, and widens to an irregular, rhombic central area. The central area has a wide transverse fascia. Striae are radiate in the center, becoming convergent toward the apices. The raphe is broadly lateral with question mark-shaped terminal fissures.


This taxon is represented by images from specimens in sediments of small lakes in Maine, New Hampshire, and Rhode Island. It was encountered in the EPA National Lakes Assessment program.

Original Description

  • Author
    Kramer 1992
  • Length Range
    48-84 µm
  • Width
    8-10 µm
  • Striae in 10µm

Original Images

Pinn subgibba var undulata org img 02
Pinn subgibba var undulata org img 01
Pinn subgibba var undulata org descp

Cite This Page

Aycock, L. (2022). Pinnularia subgibba var. undulata. In Diatoms of North America. Retrieved May 24, 2024, from https://diatoms.org/species/pinnularia-subgibba-var-undulata


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