• Category
  • Length Range
    159–272 µm
  • Width Range
    3.3–4.0 μm in the center, at apices 5.3–6.4 µm
  • Striae in 10 µm
    18–21

Identification

Description

Valves are elongate, straight, and narrowing gradually and slightly from the center to the subapical region (1.9–2.8 μm wide in the narrowest part), from which they widen abruptly into the spatulate apices. The apices are distinctly dorsally inflated and broadly rounded. Irregularly arranged siliceous ridges, or protrusions, are present at the apical margins of the valves (visible in SEM). The raphe is positioned on the valve mantle, and curves back on the valve face, where it is parallel to the ventral margin, centered with respect to the main axis of the valve. The distal raphe end is visible on the external portion of the valve, but does not penetrate the internal part of valve past the helictoglossa. There, the raphe is internally occluded by a hyaline linear area interrupting the striae. A single rimoportula is present on each valve, located adjacent to the helictoglossa and usually visible in LM. Striae are fine and parallel throughout the valve. The striae are more dense at the apices (up to 23.5 in 10 μm). Areolae are circular and externally occluded, 33–40 in 10 μm.

Autecology

To date, E. spatulata has only been observed in small acidic and oligotrophic lakes and swamps (pH 4.6–5.0, conductivity 22.0–67.8 μS) on Mount Desert Island, Acadia National Park, Maine.

Original Description

Valves are straight, narrowing very gradually and slightly from the center to the subapical portion, from which the valves widen abruptly into the widely spatulate apices (Figs 104–117), 159–272 μm long, 3.3–4.0 μm wide in center, 1.9–2.8 μm wide in narrowest part, 5.3–6.4 μm wide at apices. The apices are inflated more on the dorsal side than the ventral side and appear flattened at the ends (Figs 104–117). The valve edges are sharply beveled with one to two rows or areolae in the beveled section (Figs 120, 121, 124). Irregularly arranged siliceous ridges are present at the apical margins of the valves (Figs 119, 121–123). Raphe begins on the valve mantle, and curves subapically on the valve face back towards the main part of the valve. It is centered with respect to the main axis of the valve but closer to the ventral margin because of the unevenly widened apices (Figs 119, 121–123). External raphe fissure is visible on the external portion of the valve (e.g., Fig. 122), but does not penetrate the internal part of valve past the helictoglossa, where it is internally occluded by a hyaline linear area interrupting the striae past the helictoglossa (Figs 126, 127, 130, 131). A single rimoportula is present on each valve, and is located within the apical edge adjacent to the helictoglossa (Figs 122, 123, 127, 129), usually visible in the LM (Figs 104b, 105b, 107b). Striae are fine and parallel throughout the valve, including the apices, where they are spaced more densely (Figs 126–133), 18–21 in 10 μm, up to 23.5 in 10 μm at the ends. Areolae are circular and externally occluded (Fig. 122), 33–40 in 10 μm.

  • Author
    J.Veselá and J.R.Johans. 2014
  • Length Range
    159–272 µm
  • Width
    3.3–4.0 μm in the center, at apices 5.3–6.4 µm
  • Striae in 10µm
    18–21

Original Images

Eunotia spathulata orig illus
Eun Spathulata  Original  Descr2

Cite This Page

Veselá, J. (2017). Eunotia spatulata. In Diatoms of North America. Retrieved July 22, 2018, from https://diatoms.org/species/eunotia_spatulata

Responses

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