• Category
  • Length Range
    14-31 µm
  • Width Range
    7.5-9.9 µm
  • Striae in 10 µm
    26-32
  • Reported As
    Navicula variostriata (Hein 1990, p. 76, plate 31, figs. 7-9)
    Navicula cf. variostriata (Pienitz et al. 2003, p. 47, plate 14, fig. 6)

Identification

Description

Valves are elliptic-lanceolate with broadly rounded apices. The axial area is narrow and linear. The central area is orbicular and large, about 1/2 the width of the valve. The raphe is filiform and straight with distinctly expanded proximal ends. Distal raphe fissures are deflected abruptly in opposite directions, some distance from each apex. Striae are radiate throughout and alternately long and short around the central area. Areolae in the striae adjacent to the central area tend to be larger than areolae elsewhere and somewhat elongate transapically. Areolae number 26-35 in 10 µm. Internally, under SEM, proximal raphe ends are T-shaped and areolae are occluded by hymenes.

Autecology

Cavinula davisiae is documented here from the Pacific Northwest. Besides the type locality (photo below), C. davisiae has been confirmed from a stream in southwest Montana and a small pool in Waterton Lakes National Park, Alberta (Montana Diatom Collection). This species has been misidentified as Navicula variostriata Krasske and is probably more widespread than our records show. Hein (1990) reported it (as N. variostriata) from Adak Island, Alaska, and Pienitz et al. (2003) reported it (as N. cf. variostriata) from islands off the Pacific Coast of western British Columbia, Canada. It appears to prefer oligotrophic or dystrophic waters with circumneutral pH and low conductivity.

Clover  Lake By Flickr
Credit: flickr
Clover Lake, Mount Rainier National Park, Pierce County, Washington: type locality for Cavinula davisiae.

Original Description

Valves elliptic-lanceolate with broadly rounded apices. Valve length 14–31 μm; valve width 7.5–9.9 μm. Axial area narrow and linear; central area orbicular and large, about 1/2 valve width. Raphe filiform and straight with distinctly expanded proximal ends. Terminal raphe fissures hooked abruptly in opposite directions some distance from each apex. Striae radiate throughout, alternately long and short around the central area, 26–32 in 10 μm. Areolae round, 26–35 in 10 μm. Areolae of striae adjacent to central area larger and somewhat elongate transapically. Internally, proximal raphe ends T-shaped and areolae occluded by hymenes.

  • Author
    Bahls 2013
  • Length Range
    14-31 µm
  • Width
    7.5-9.9 µm
  • Striae in 10µm
    26-32

Original Images

Cavinula davisiae orig illus
Cavinula davisiae orig descr

Cite This Page

Bahls, L. (2012). Cavinula davisiae. In Diatoms of North America. Retrieved July 21, 2018, from https://diatoms.org/species/cavinula_davisiae

Responses

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