• Category
  • Length Range
    78-105 µm
  • Width Range
    18.0-19.3 µm
  • Striae in 10 µm
    14 (center) to 17 (apices); 10-15 Heribaudii stage

Identification

Description

Valves are lanceolate with rostrate to subcapitate apices. The axial area is narrow. The central area is elliptic and slightly wider than the axial area. The raphe is filiform and somewhat sinuous, with inflated and relatively distant proximal raphe ends. Striae are parallel in the middle of the valve, becoming weakly radiate and then convergent near the apices. One or more striae in the central area are slightly shorter than adjacent striae. Areolae are distinct in LM and number a constant 28 in 10 µm. Valves with a Heribaudii stage were also present in the population observed. Craticula, however, were not observed.

Autecology

Craticula johnstoniae evidently tolerates a wide range in water quality. It has been collected from a circumneutral pond (pH 6.98) with low specific conductance (46 µS/cm) and from an alkaline pond (pH 8.1-11.1) with moderate specific conductance (302-313 µS/cm). At these locations it was found in association with Craticula cuspidata, C. acidoclinata, and C. sardiniana

Akamina  Pools 1
Credit: Barb Johnston, Parks Canada
Akamina Pools, Waterton Lakes National Park, Alberta: home of Craticula johnstoniae.

Original Description

Valves lanceolate with rostrate to subcapitate apices. Valve length 78–105 μm; valve width 18.0–19.3 μm. Axial area narrow, flaring somewhat to merge with an elliptic and slightly wider central area. Raphe filiform and somewhat sinuous with inflated and relatively distant proximal ends that are bent to the same side. Striae parallel in the middle, becoming weakly radiate and then convergent near the apices, 14 in 10 μm at valve center, 17 in 10 μm at the apices. One or more striae in the central area slightly shorter than adjacent striae. Areolae 28 in 10 μm. “Heribaudii” valves present with more strongly radiate striae and lower stria density; craticula valves not observed.

  • Author
    Bahls 2013
  • Length Range
    78-105 µm
  • Width
    18.0-19.3 µm
  • Striae in 10µm
    14 at valve center, 17 at the apices

Original Images

Craticula johnstoniae orig illus
Craticula johnstoniae orig descr

Cite This Page

Bahls, L. (2012). Craticula johnstoniae. In Diatoms of North America. Retrieved June 24, 2018, from https://diatoms.org/species/craticula_johnstoniae

Responses

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