• Reported As
    Navicula pseudocrassirostris (Wachnicka et al. 2011)
    Envekadea pseudocrassirostris (Lee et al. 2013)

Identification

Description

Valves are linear, with a tumid center. The apices are protracted and rounded. The axial area is wide at the ends of the valve, but very narrow at the center. The central area is slightly raised above the rest of the valve face. The raphe is weakly lateral and straight except for at the apices, where it becomes sigmoid. External proximal raphe ends are widely T-shaped and terminate close to one another. External distal raphe ends are slightly expanded, positioned within a wide groove. The distal raphe ends are surrounded by a hyaline area, and are deflected to opposite sides. Internally, the raphe is straight. Internal proximal raphe ends are deflected to the same side. The internal distal raphe ends terminate in reduced helictoglossae.

Transapical striae are indistinctly puncate, strongly radiate in the center of the valve, and strongly convergent near the apices. Striae in the center of the valve are composed of interspersed short and long striae. Striae are continuous over the valve mantle. External striae are composed of irregularly formed, rectangular to polygonal areolae. Internally, the areolae are round and unoccluded.

Autecology

Envekadea vanlandinghamii was described from the main basin of Blue Lake Warm Springs, Utah, with high conductance (9320 µS/cm) and close to neutral pH (7.6 pH).

Envekadea vanlandinghamii was found at low abundance (<1%) in a periphyton assemblage that included green algae and bladderwort. The site in Everglades National Park had 3900 µS/cm conductivity, 6.5 pH, and 270 µg/g total phosphorus. Other diatom taxa within the assemblage were E. metzeltinii, Fragilaria synegrotesca, Mastogloia lanceolata, and M. calcarea (Lee et al. 2013).

Original Description

Valves linear, tumid in the center, with apices protracted, rounded (Figs 76–83). Length 32.0–67.0 µm, breadth 7.0–8.5 µm. Apical breadth 4.0–6.0 µm. Axial area wide at the ends of the valve, very narrow to the center where it is only slightly wider and bordered on either side by striae that are more coarse than the others and of various lengths. The raphe is weakly lateral with external proximal ends terminating close to one another and distal ends deflected in opposite directions (Figs 76, 79, 81). Striae are indistinctly punctate, strongly radiate around the center, strongly convergent towards the poles (Figs 79, 81). Striae 17–23/10 µm in the center, 27–29/10 µm at the ends.

In the SEM, the valve exterior is dominated by the striae with their volate occlusions (Fig. 85) and a sharp change in orientation from radiate at the center to convergent at the ends (Fig. 84). The raphe branches and axial area are S-shaped (Fig. 84). Proximal raphe ends are widely T-shaped (Fig. 86). The terminus of the axial area is wide and more developed on one side than the other (Fig. 85). Internally, the axial area is narrow and thickened (Fig. 87). Helictoglossae are fine, with the end pointed inward (Fig. 88). Proximal raphe ends terminate close to one another (Fig. 89).

  • Author
    Graeff, Kociolek and Rushforth 2013
  • Length Range
    32-67 µm
  • Width
    7-8.5 µm
  • Striae in 10µm
    17-23

Original Images

Graeffetal  Original Image  Envekadeavanlandinghamii
Graeffetal  Original Description  Envekadeavanlandinghamii

Cite This Page

Lee, S, and Van de Vijver, B. (2015). Envekadea vanlandinghamii. In Diatoms of North America. Retrieved July 21, 2018, from https://diatoms.org/species/envekadea_pseudocrassirostris

Responses

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