• Category
  • Length Range
    10.3-20.4 µm
  • Width Range
    3.7-4.4 µm
  • Striae in 10 µm
    24-28 in the center of raphe valve, 26-32 in the center of rapheless valve, 35-42 at the ends



Valves are linear-lanceolate with subrostrate ends. The raphe valve is concave with a linear axial area, which widens slightly in the middle portion of the valve. The terminal raphe fissures are hooked towards the same side of the valve. The central raphe ends are teardrop-shaped externally and curve to opposite sides internally. The rapheless valve is convex with a narrow, linear axial area widening slightly in the middle. Striae are parallel or very slightly radiate throughout both valves. Striae 24-28 in 10 µm in the middle and 35-42 in 10 µm at the apices of the raphe valve. Striae 26-32 in 10 µm in the middle and 35-40 in 10 µm at the apices of the rapheless valve. The external openings of the areolae are transapically elongated, appearing as narrow slits. Each stria in the middle part of the valve is composed of 4-5 areolae.


Original Description

Valves 9-27 μm long, 2.5-5 μm wide, with 19-22 striae in 10 μm at valve center, 29-31 striae in 10 μm at the ends on both the raphe and pseudoraphe valve. Valves linear, with subrostrate ends. Smaller specimens becoming rounded with no distinct ends. Raphe filiform, with distal raphe ends deflecting in the same direction. Differs from the nominate variety in the widely spaced median striae.

  • Basionym
    Achnanthes deflexa var. alpestris
  • Author
    R.L.Lowe and Kociolek 1984
  • Length Range
    9-27 µm
  • Width
    2.5-5 µm
  • Striae in 10µm
    19-22 in the center valve, 29-31 at the ends

Original Images

Orig Ill001 6
Orig Desc001

Cite This Page

Potapova, M. (2010). Achnanthidium alpestre. In Diatoms of North America. Retrieved June 23, 2024, from https://diatoms.org/species/achnanthidium_alpestre


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