• Category
  • Length Range
    9.9-21 µm
  • Width Range
    3-3.5 µm
  • Striae in 10 µm
    28-30 in raphe valve, 22-25 in rapheless valve



Valves are elliptical to linear-ellitical. The raphe valve is concave with a linear axial area, which widens slightly in the middle portion of the valve. The raphe is straight without the terminal raphe fissures. The central raphe ends are simple externally, not expanded. Internally, the central raphe ends curve toward opposite sides. The striae are strongly radiate throughout the raphe valve, 28-30 in 10 µm in the middle and up to 40 in 10 µm at the apices. In the middle of the valve the striae are interrupted to form a transverse fascia. The rapheless valve is convex. It has a narrow, linear axial area and no central area. Striae are parallel throughout the rapheless valve, becoming slightly radiate at the apices, 22-25 in 10 µm. The external openings of the areolae are transapically elongated to almost isodiametric. Striae have a maximum of 4-5 areolae on the valve face and one areola on the margin of both rapheless and raphe valves.


Original Description

Schalen schmal linear, selten gegen die Enden etwas lanzettlich verschmälert, an den Polen stumpf gerundet, 7-16 μ lang, 2,5-3 μ breit. Raphenschale mit gerade, fadenförmiger Raphe, Axialarea sehr eng, Zentralarea eine bis an den Rand reichende Querbinde von wechselnder Breite. Transapicalstreifen kräftig, durchweg ziemlich stark radial, 28-30 in 10μ. Raphelose Schale mit sehr enger Pseudoraphe, ohne Zentralarea, Transapicalstreifen senkrecht zur Mittellinie oder nur wenig radial, gröber als auf der Rapheschale, 22-25 in 10 μ, zart aber deutlich punktiert.

  • Basionym
    Achnanthes atomus
  • Author
    Hust. 1937
  • Length Range
    7-16 µm
  • Width
    2.5-3 µm
  • Striae in 10µm
    28-30 on raphe valve, 22-25 on rapheless valve

Original Images

Orig Ill  Ahatomus
Orig Descr 5

Cite This Page

Potapova, M. (2010). Achnanthidium atomus. In Diatoms of North America. Retrieved June 23, 2018, from https://diatoms.org/species/achnanthidium_atomus


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