• Category
  • Length Range
    73-110 µm
  • Width Range
    17.1-20.4 µm
  • Striae in 10 µm
  • Reported As
    Tropidoneis lepidoptera var. javanica (Hustedt 1938)



Valves are lanceolate with an arched valve face. The valve face has longitudinal folds and apiculate apices. The narrow axial area and raphe are positioned on the apex of a raised keel that runs along the apical axis. The central area is asymmetric and about one-half the width of the valve. The raphe is filiform with simple proximal and distal ends. Proximal raphe ends are straight and positioned close to one another. Striae are parallel at the center, becoming increasingly radiate towards the apices. The striae may appear wavy because of valve contours. Areolae are difficult to resolve in LM and number 26-30 in 10 µm.


Plagiotropis lepidoptera var. proboscidea has been found in 37 samples collected from streams on the Northwestern Great Plains. The mean pH of these waters is 8.3 and the mean specific conductance is 4389 µS/cm. These waters have elevated concentrations of sodium (mean = 613 mg/L), sulfate (mean = 1307 mg/L), iron (mean = 1560 µg/L), and manganese (mean = 1944 µg/L). Common diatom associates include Navicula namibica, Planothidium engelbrechtii, Bacillaria paradoxa, Navicula peregrina, Staurophora brantii, Nitzschia siliqua, Entomoneis alata, and Tryblionella compressa. Patrick and Reimer (1975) report this taxon as widespread in the United States in alkaline streams. It was described from material collected in Cameroun, Africa (Cleve 1894).

Original Description

  • Basionym
    Tropidoneis lepidoptera var. proboscidea
  • Author
    Cleve 1894
  • Length Range
    75 µm
  • Width
    18 µm
  • Striae in 10µm

Original Images

Plagiotropis Proboscidea  Orig Descr

Cite This Page

Bahls, L. (2012). Plagiotropis lepidoptera var. proboscidea. In Diatoms of North America. Retrieved June 23, 2024, from https://diatoms.org/species/plagiotropis_lepidoptera_var._proboscidea


The 15 response plots show an environmental variable (x axis) against the relative abundance (y axis) of Plagiotropis lepidoptera var. proboscidea 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.