• Category
  • Length Range
    24.5-41.2 µm
  • Width Range
    6.9-8.9 µm
  • Striae in 10 µm
    10-12 at the valve center, up to 14 near the apices



Valves are lanceolate and dorsiventral with narrowly rounded, unprotracted apices. The dorsal margin is moderately arched; the ventral margin is slightly convex to nearly flat in the smallest specimens. The axial area arched and located ventral to the valve mid line. The central area is a slightly wider continuation of the axial area. Proximal raphe ends are reverse-lateral, deflected ventrally, and terminate with inflated pores. Terminal raphe fissures are deflected dorsally at about 45 degrees. Striae are slightly radiate at the valve center, becoming more strongly radiate near the apices. Areolae number 24-28 in 10 µm. A single isolated stigma (occasionally 2) is located at the end of the median stria on the ventral side.


Specimens of C. parva pictured on this web page are from Logging Creek, a mountain stream on the west side of Glacier National Park, Montana. On the date of collection, Logging Creek had a pH of 7.74 and a specific conductance of 50 µS/cm. Krammer (2002) reports this taxon as a nordic-alpine species that prefers oligotrophic waters with lower to average electrolyte content. Illustrations by Smith (1853) show that this taxon lives in colonies and produces branched and unbranched stalks.

Original Description

  • Basionym
    Cocconema parvum
  • Author
    W.Sm. 1853

Original Images

Plate Xxiv Fig 222  Cocconema Parvum  Smith1853
Page76  Smith1853  Cocconema Parvum  Smith1853

Cite This Page

Bahls, L. (2016). Cymbella parva. In Diatoms of North America. Retrieved July 13, 2024, from https://diatoms.org/species/cymbella_parva


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