Identification

Description

Valves are lanceolate to linear-lanceolate. The apices are protracted and narrowly rostrate. The axial area is moderately wide and linear, expanding slightly near the central area. The central area (in Northern Rockies specimens) is a narrow rectangular stauros, hardly expanded toward valve margins and sometimes with shortened striae. The raphe is lateral. Proximal raphe ends are weakly expanded, weakly deflected, and widely spaced (they do not extend into the central area). Striae are radiate throughout. Areolae are variably spaced and number 20-28 in 10 µm.

Stauroneis anceps is one of the most commonly misidentified Stauroneis species in North America. Reichardt (1995) designated the lectotype for this species (Tafel 16, fig. 1) from a population (Sippe 1) in Ehrenberg's type material from Cayenne, French Guyana. Similar forms present in Ehrenberg's type material (Sippe 2 and Sippe 3) were later described as Stauroneis reichardtii (Lange-Bertalot et al. 2003). Specimens of S. anceps from the Northern Rockies tend to be somewhat larger, have a lower stria density and a smaller stauros than specimens of Sippe 1 in the type population, but they are otherwise quite similar. Until further work is completed, we consider the population of S. anceps described here to represent this species as described by Reichardt (1995) from Ehrenberg's type material.

Autecology

In the Northern Rockies, Stauroneis anceps is found in lakes and ponds with circumneutral pH (mean pH = 6.9) and very low specific conductance (mean SC = 17 µS/cm).

Bloody  Dick  Pond 2
Credit: Loren Bahls
Bloody Dick Pond No. 2, Beaverhead County, Montana: home of Kurtkrammeria coxiae.

Original Description

  • Author
    Ehrenb. 1843
  • Length Range
    40-70 µm
  • Width
    10-13 µm
  • Striae in 10µm
    22-24

EMAP Assessment

EMAP Distribution

Stauroneis Anceps 40
Map 40

Response Plots

Stauroneis Anceps

Cite This Page

Bahls, L. (2011). Stauroneis anceps. In Diatoms of North America. Retrieved August 18, 2018, from https://diatoms.org/species/stauroneis_anceps

Responses

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