• Category
  • Length Range
    130-360 µm
  • Width Range
    35-68 µm
  • Striae in 10 µm
  • Synonyms
    Cocconema janischii Schmidt
    Cymbella mexicana var. janischii (Schmidt) Reimer



Valves with a highly arched dorsal margin, ventral margin is straight, with a tumid area in the center. The axial area is narrow and slightly enlarged at the center to form an ovoid to irregular central area. The raphe is lateral, with dilated external proximal ends and distal ends deflected towards the dorsal margin. A single stigma is positioned in the central nodule, between the proximal raphe ends. The areolae near the central area are elongated, especially on the ventral side. Striae are radiate and coarsely punctate. Distinct apical pore fields are present at each apex.

Note: The longer valve length indicated here as compared to Patrick and Reimer up to 295 µm, 1975, p. 60) is due to our observation of an initial valve in the sample. Reimer’s suggestion that this species is closely allied with C. mexicana is not supported by published observations, and we have chosen to keep this as a separate species.


Original Description

  • Basionym
    Cocconema janischii
  • Author
    A.Schmidt 1881

Original Images

Cocconema janischii orig illus

Cite This Page

Kociolek, P. (2011). Cymbella janischii. In Diatoms of North America. Retrieved July 13, 2024, from https://diatoms.org/species/cymbella_janischii


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