• Category
  • Length Range
    7-20 µm
  • Width Range
    4-8.5 µm
  • Striae in 10 µm



Valves are linear-elliptical with rostrate, subrostrate or narrowly subcapitate apices. The raphe valve has a linear axial area and transversely rectangular central area. The rapheless valve has a narrow, linear axial area. The asymmetric central area on the rapheless valve contains a shallow depression on the internal valve surface. The raphe is straight with expanded external proximal endings. The striae are radiate throughout both valves.


Original Description

A. lanceolata var. dubia GRUN. (Achnanthidium delicatulum KG. ex parte?) Steht der vorigen Art sehr nahe, und unterscheidet sich fast nur durch die kurzen, breit lanzettlichen kurz zugespitzten Schaalen, und den etwas schmäleren Pseudostauros der unteren Schaalen. Querstreifen 13-14 in 0,01 mm. Länge 0,015-0,017 mm., Breite 0,007-0,0072 mm. Buchberg in Unterösterreich, Belgien.

  • Basionym
    Achnanthes lanceolata var. dubia
  • Author
    Grunow 1880
  • Length Range
    15-17 µm
  • Width
    7-7.2 µm
  • Striae in 10µm

Original Images

Pl Dubium  Orig Ill
Pl Dubium  Orig Descr

EMAP Assessment

EMAP Distribution

Planothidium Dubium   Grunow   Round Et  Bukhtiyarova 3
Map 3

Response Plots

Planothidium Dubium   Grunow   Round Et  Bukhtiyarova

Cite This Page

Potapova, M. (2011). Planothidium dubium. In Diatoms of North America. Retrieved February 22, 2020, from https://diatoms.org/species/planothidium_dubium


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