• Category
  • Length Range
    5.6-20.8 µm
  • Width Range
    1.5-3.3 µm
  • Striae in 10 µm



Cells are solitary or in very short chains, often attached to substrate by a stalk. Frustules are monoraphid with a concave raphe valve and convex rapheless valve. Valves are linear-lanceolate with slightly drawn-out or slightly capitate ends, 1.5-3.3 µm wide, 5.6-20.8 µm long. Central external raphe ends are simple, terminal raphe fissures are short, almost straight, or absent. Internally, the central raphe ends are turned in opposite directions. Striae are radiate throughout both valves, 25-35 in 10 µm. Striae consist of one row of areolae. The striae are often interrupted in the central part of raphe valve to form a symmetrical or asymmetrical fascia. One row of elongated areolae is present on the valve mantle. External areolae openings of areolae vary in shape from circular to transapically elongated slits. Internal openings of the areolae are elliptical, occluded by hymens perforated by small pores. Girdle bands are plain, open.


Original Description

Stipite brevissimo; corpusculis minutissimis parum curvatis lutescentibus, e frustulis plerumque binis constitutis.

  • Basionym
    Achnanthes minutissima
  • Author
    Kütz. 1833

Original Images

Achnanthes minutissima orig illus
Achnanthes minutissima orig descr

Citations & Links



Cite This Page

Potapova, M. (2009). Achnanthidium minutissimum. In Diatoms of North America. Retrieved June 17, 2024, from https://diatoms.org/species/achnanthidium_minutissimum


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