• Category
  • Length Range
    10-18 µm
  • Width Range
    5.4-7.1 µm
  • Striae in 10 µm



Frustules are often strongly bent in the girdle view with concave raphe valve and convex rapheless valve. Valves are elliptical-lanceolate with slightly drawn-out ends. The raphe valve has a narrow axial area and an asymmetrical central area, which is usually expanded to the valve margin on one side. The raphe is straight or slightly sigmoid with terminal ends sharply turned to opposite directions. Rapheless valve has a narrow linear or slightly sigmoid axial area and a large central area of variable shape, often asymmetrical an expanded to one or both valve margins. Sometimes a shallow depression is visible on one side of the central area. The striae are radiate, 25-35 in 10 μm.

Note that this concept of E. laevis is wide and includes types of E. quadratarea (Ostrup) Lange-Bertalot in Lange-Bertalot and Genkal, E. diluviana (Hustedt) Lange-Bertalot in Lange-Bertalot and Genkal, and E. lapponica Hustedt. North American researchers have referred this taxon to Achnanthes lapponica var. ninckei (Guerm. and Mang.) Reimer [Syn.: Eucocconeis lapponica var. ninckei (Guerm. and Mang.) Stoermer and Yang 1969] based on its treatment in Patrick and Reimer (1966). Further investigation is necessary to establish whether these taxa represent separate species.


Original Description

Long. 13 μ, Lat. 5,5 μ. Striis subtilissimis. Valva elliptica, apicibus subtruncatis. Epitheca: Area apicali angusta, lineari. Striis inconspicuis. Hypotheca: Raphe area apicali hyalina, angustissima, media in parte valvæ subito dilatata, cincta. Striis media modo in parte valvæ conspicuis.

  • Basionym
    Achnanthes laevis
  • Author
    Østrup 1910
  • Length Range
    13 µm
  • Width
    5.5 µm

Original Images

Eucocconeis laevis orig illus
Eulaevis  Orig Desc

EMAP Assessment

EMAP Distribution

Eucocconeis Laevis 40 Copy
Map 40

Response Plots

Eucocconeis Laevis Copy

Cite This Page

Potapova, M. (2010). Eucocconeis laevis. In Diatoms of North America. Retrieved July 22, 2018, from https://diatoms.org/species/eucocconeis_laevis


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