• Category
  • Length Range
    10-25 µm
  • Width Range
    7-11 µm
  • Striae in 10 µm
    24-28 on raphe valve, 16-22 on rapheless valve
  • Synonyms
    Achnanthes peragalloi Brun and Hérib.
    Planothidium peragalloi (Brun and Hérib.) Round and Bukht.



Valves are elliptic-lanceolate, with subrostrate to subcapitate apices. The raphe valve has a narrow linear axial area and a wide, bowtie-shaped central area. The raphe is straight and filiform. The external proximal raphe ends are straight. The striae on the raphe valve are uniseriate, and strongly radiate, much denser than striae on the rapheless valve. Short and long striae alternate around the central area. The rapheless valve has a wide cavum. The rapheless valve also has a wide lanceolate axial area bordered by biseriate striae.


This taxon typically forms populations in low abundance, although it appears to be widespread. It has been reported from EPA and USGS surveys in western North America, southeast states, and California. The images presented here are from specimens in rivers and lakes of Delaware, Maine, Massachusetts, South Carolina and Vermont.

Original Description

Espèce très petite. Longueur 12 á 16 μ; largeur 6 á 8 μ. Frustule elliptique, á terminaisons capitulées on simple-ment rostrées. La valve supérieure porte des stries larges, peu convergentes et lisses. Ces stries s'atténuent subite-rnent dans la région médiane, environ á mi-distance de la marge an centre. La valve inférieure porte des stries plus fines et plus serrées (comme chez l’Ach. Clevei Grun.) et très convergentes; elles laissent un large nodule central qui s'évase considérablement, en cônes rectilignes, jus-qu'aux flancs de la valve. Sur l’un des côtés du frustule se trouve un demi-cercle très nettement marqué, interposé entre les deux valves et n'interrompant pas les stries de la face supérieure (comme chez l’Ach. lanceolata). Face connective très peu courbée, presque rectiligne.

  • Basionym
    Achnanthes peragalloi
  • Author
    Brun and Hérib. in Hérib. 1893
  • Length Range
    12-16 µm
  • Width
    6-8 µm

Original Images

Planperag  Orig Ill

Cite This Page

Potapova, M. (2019). Skabitschewskia peragalloi. In Diatoms of North America. Retrieved September 19, 2019, from https://diatoms.org/species/skabitschewskia_peragallii


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