• Category
  • Length Range
    43-64 µm
  • Width Range
    16.9-19.6 µm
  • Striae in 10 µm
  • Reported As
    Navicula tuscula (Patrick and Reimer 1966, p. 539 [in part], pl. 52, fig. 7)
    Navicula tuscula (Krammer and Lange-Bertalot 1986, p. 234 [in part], fig. 24: 1; figs. 81: 3,8)



Valves are broadly lanceolate to elliptic-lanceolate with rostrate apices. Axial area is narrow and linear. Central area is a rectangular transverse fascia delimited by 3-5 unevenly shortened striae on each side. The raphe is filiform to weakly lateral and straight to slightly undulate. Proximal raphe ends are dilated. Striae are radiate throughout. Areolae are transversely elongate in the central region and irregularly spaced where they number 8-10 in 10 µm, becoming more densely and evenly packed near the valve margin. Areolae are secondarily aligned in wavy longitudinal rows.


Aneumastus rostratus has been collected from several lakes and ponds in Glacier National Park, Montana and Waterton Lakes National Park, Alberta. Here pH ranges from 7.08 to 8.54 and specific conductance ranged from 92 to 183 µS/cm. In Europe, Lange-Bertalot (2001) reports optimum conditions for this species in electrolyte-rich to brackish waters near the coasts.

Redrock  L
Credit: Loren Bahls
Redrock Lake, Glacier National Park, Montana: home of Aneumastus rostratus.

Original Description

Valva elliptica, apicus subrostratis. Tab. III, Fig. 22. 880/1.

  • Basionym
    Navicula tuscula var. rostrata
  • Author
    Hust. 1911

Original Images

Navicula Tuscula Rostrata Orig Illus
Navicula Tuscula Rostrata Orig Des

Cite This Page

Bahls, L. (2012). Aneumastus rostratus. In Diatoms of North America. Retrieved May 29, 2024, from https://diatoms.org/species/aneumastus_rostratus


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