• Category
  • Length Range
    185–335 µm
  • Width Range
    29–44 µm
  • Striae in 10 µm
    5–6 throughout the valve, up to 9 around central area



Valves are linear-lanceolate, with a central inflation and rounded apices, subcapitate to capitate in larger specimens. Valve length to width ratio is 6.5–8. The axial area is linear-lanceolate and approximately 1/3 of the valve width. The central area is round or elliptic, asymmetric, and wider on the primary side of the valve. The raphe is lateral, with external raphe slits that are only slightly curved. The central pores are small and round. Terminal raphe fissures are sickle-shaped, extending onto the valve mantle. Striae (alveoli) are radiate in the valve center and convergent at the apices.

On the external valve surface, the alveoli are covered by silica plates perforated by pores arranged in 6–8 rows. Internal alveoli openings are short, 1/4–1/3 of alveolus length mid-way between valve center and apex, longer in valve center and at apices. Longitudinal lines formed by the borders of the internal alveoli openings are visible in LM and transect striae in the middle. Striae continue to the valve mantle without interruption at the valve face and mantle.


Pinnularia ectorii is found in lakes with clear, circumneutral water and low nutrient and chlorophyll concentrations. It is found in recent sediments of 15% of lakes that were sampled in the northeastern US and is also common in Quaternary lacustrine deposits (Potapova et al. 2022).

Original Description

  • Length Range
    185–335 µm
  • Width
    29-44 µm
  • Striae in 10µm

Original Images

Pinn Ectorii Orig Illustration
Pinn Ectorii Orig Description

Cite This Page

Potapova, M., Aycock, L., Kersey, M. (2023). Pinnularia ectorii. In Diatoms of North America. Retrieved May 24, 2024, from https://diatoms.org/species/pinnularia-ectorii


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