• Category
  • Length Range
    10-28 µm
  • Width Range
    3.6-6.6 µm
  • Striae in 10 µm
  • Reported As
    Achnanthes subrostrata var. appalachiana (Potapova 2011, pg. 76, Figs 28-39)



Valves are lanceolate to linear-lanceolate with slightly drawn-out ends. Raphe is absent on one valve. The rapheless valve has narrowly rhomboid axial area, which sometimes widens in the middle portion of the valve to form asymmetrical central area. The axial area of the rapheless valve has siliceous thickenings and depressions. The raphe valve has narrowly lanceolate axial area and circular or elliptical, often asymmetrically expanded central area. The raphe has a slightly curved external and straight internal slit. The proximal raphe ends are slightly expanded externally. Internally, the proximal raphe ends are bifurcated and turned sharply backwards. Striae are radiate through both valves, 20-24 in 10 μm. The external openings of the areolae are covered by the kidney-shaped hymens.

Note that examination of the holotype of Achnanthes subrostrata var. appalachiana Camburn and Lowe show diatoms that correspond to N. lapidosa (Potapova 2011). Consequently, A. subrostrata var. appalachiana is considered to be conspecific with N. lapidosa.


Original Description

Lanzettlich, Enden leicht vorgezogen. Die Langsarea beider Schalen erweitert sich lanzettlich nach der Mitte, um hier eine rundliche Zentralarea zu bilden, die auf der Oberschale, bei manchen Exemplaren auch auf der Unterschale einseitig durch das Fehlen der Mittelstreifen bis an den Rand erweitert ist. Streifen strahlend, 16 in 10 μ auf der Oberschale, 18 in 10 μ auf der Unterschale; auf dieser nach den Enden enger werdend, hier 20 in 10 μ. Lang 20-24 μ, breit 6-7 μ.

  • Basionym
    Achnanthes lapidosa
  • Author
    Krasske 1929
  • Length Range
    20-24 µm
  • Width
    6-7 µm
  • Striae in 10µm
    16 in 10 μm in upper valve, 18 in 10 μm in lower valve, 20 in 10 μm towards the ends

Original Images

Orig Ill  N Lapidosa
Orig Descr001 2

Cite This Page

Potapova, M. (2010). Nupela lapidosa. In Diatoms of North America. Retrieved May 20, 2024, from https://diatoms.org/species/nupela_lapidosa


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