• Category
  • Length Range
    18.9-22.8 µm
  • Width Range
    9.2-10.8 µm
  • Striae in 10 µm
    30-36 in 10 µm at the valve center, including short striae; a little closer at the apices
  • Reported As
    Navicula pusio (Krammer and Lange-Bertalot 1986, p. 195, plate 70, figs. 19-21)



Valves are elliptic with wide, rostrate apices. The axial area is very narrow, hardly wider than the raphe. The central area is narrow and rectangular in the apical axis. Raphe branches are pin-shaped and widen gradually from the apices toward the proximal ends, which are distinctly inflated. Distal raphe ends are bent in opposite directions (confirmed under SEM). Striae are radiate throughout. Alternately long and short striae surround the central area. Areolae are round, fine and difficult to resolve in LM.


Cavinula pusio has been collected from five springs and small headwater streams in the northern Rocky Mountains. Krammer & Lange-Bertalot (1986) describe it as an uncommon northern-alpine species in Europe, where it prefers oligotrophic waters with low electrolyte content.

Original Description

V. elliptical, with broad rostrate ends. L. 0,016; B. 0,007 mm. Axial area very narrow. Central area small. Striae very fine, about 30 in 0,01 mm. radiate at the ends, in the middle alternately longer and shorter, closer towards the ends. - Pl. II f. 3.

  • Basionym
    Navicula pusio
  • Author
    Cleve 1895
  • Length Range
    16 µm
  • Width
    7 µm
  • Striae in 10µm

Original Images

N Pusio Orig Ill
N Pusio Origdes

Cite This Page

Bahls, L. (2012). Cavinula pusio. In Diatoms of North America. Retrieved August 20, 2018, from https://diatoms.org/species/cavinula_pusio


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