• Category
  • Length Range
    13-18.5 µm
  • Width Range
    3.5-4.5 µm
  • Striae in 10 µm
  • Synonyms
    Achnanthes petersenii Hust.



Valves are linear or linear-elliptical with rounded ends. The raphe valve has a narrow axial area and a large rectangular or transversely elliptical central area that almost reaches the valve margins. The raphe is straight, filiform, and lacks terminal fissures. Internally, the central raphe endings are curved to opposite sides. The rapheless valve has a narrowly rhomboid axial area and no distinct central area. Striae are uniseriate and slightly radiate. Each stria in the middle part of the valve contains 5-7 areolae. The valve mantle bears one row of areolae.


Original Description

Zellen mit schwach verkieselten Membranen, sehr hyalin. Schalen linear-elliptish, gegen die breit gerundeten Enden etwas verschmälert, 12-17 µ lang, 3,5-4 µ breit. Raphenschale mit gerader, fadenförmiger Raphe, Axialarea sehr eng, Zentralarea eine breite, bisanden Schalenrand reichende Querbinde. Transpikalstreifen im mittleren Teil etwa 36 in 10 µ, gegen die Pole enger werdend, bis etwa 40 in 10 µ, durchweg leicht radia. Raphenlose Schale mit schmal linearer, zuweilen in der Mitte etwas erweiterer Pseudoraphe, Transapikalstreifen etwas gröber, im mittleren Teil etwa 30 in 10 µ, gegen Enden ebenfalls enger werdend, durchweg radial. Fig. 10-14.

  • Basionym
    Achnanthes petersenii
  • Author
    Hust. 1937
  • Length Range
    12-17 µm
  • Width
    3.5-4 µm
  • Striae in 10µm
    36 in the middle, about 40 at the poles

Original Images

Achnanthes petersenii orig illus
Achnanthes petersenii orig descr

Cite This Page

Potapova, M. (2010). Rossithidium petersenii. In Diatoms of North America. Retrieved July 19, 2024, from https://diatoms.org/species/rossithidium_petersenii


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