• Category
  • Length Range
    24-28 µm
  • Width Range
    5.6-5.9 µm
  • Striae in 10 µm



Valves are linear, with triundulate sides. The central inflation is the same width as the distal inflations. The apices are small and subcapitate. The raphe is straight, with comma shaped terminal fissures. The axial area is narrow and gradually widens to a rhombic central area with a transverse fascia. Striae are radiate in the center becoming convergent toward the apices.


This taxon was originally described from an oligotrophic lake in Finland ( ). The images here are from sediments of a pond in Maine.

Original Description

Valves linear, margins moderately triundulate, the central inflation equally wide as the other two, ends small subcapitate, length 26-30 µm, breadth 6.3-6.7 µm, length-to-breadth ratio 4.5. Raphe branches straight, central pores lateral deflected, terminal fissures probable ?-shaped. Axial area narrow, central area rhombic, widened to a small fascia. Striae radiate in the middle becoming convergent towards ends, 12-13/10µm.

Distribution: Known only from the type locality.

Distinguished from P. pluviana by the length-to-breadth ratio, the finer striation and the different shape of the areae.

  • Author
    Krammer 2000
  • Length Range
    26-30 µm
  • Width
    6.3-6.7 µm
  • Striae in 10µm

Original Images

Pinn pluvianiformis org img
Pinn pluvianiformis org descp

Cite This Page

Aycock, L. (2022). Pinnularia pluvianiformis. In Diatoms of North America. Retrieved May 30, 2024, from https://diatoms.org/species/pinnularia-pluvianiformis


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