• Category
  • Length Range
    68-111 µm
  • Width Range
    17.5-21.0 µm
  • Striae in 10 µm
    26–28 in the center, 28 at the ends

Identification

Description

Valves rhomboid with a very slight constriction near the rounded poles. Striae are mostly parallel, but slightly convergent and may be wavy at apices. Externally, areolae lanceolate or round with the most rounded areolae positioned near the valve center. Adjacent to external central area, areolae may be slightly expanded. Internally, areolar openings are round. Areolae circumradiate the apices, but the striae are greatly reduced. Longitudinal striae are parallel over the majority of the valve face, but become slightly wavy at the valve center. External central area possessing an irregular grouping of small poroids, varying in number. Rows of areolae adjacent to either side of raphe terminate before distal raphe end. The areola density is 26 in 10 µm. Internal longitudinal ribs are robust and widen significantly, but smoothly, at the central area before becoming constricted at the central nodule. Longitudinal ribs widen very abruptly near the apices, then terminate bluntly at the helictoglossa. Longitudinal ribs fuse with the linear helictoglossa to form a wide, prominent porte-crayon structure. External proximal raphe ends are expanded into shallow, crescent-moon shapes.

Autecology

Original Description

Valves rhomboid with a very slight constriction near rounded poles; 68.0–111.0 μm long, 17.5–21.0 μm wide. Striae with density of 26–28 in 10 μm at valve centre, 28 in 10 μm at valve ends. Striae mostly parallel but slightly convergent and sometimes wavy at apices (Figs 42 and 44). Externally, areolae lanceolate or round (Figs 51 and 52) with the most rounded areolae being located near valve centre (Fig. 52). Adjacent to external central area, areolae can be slightly expanded (Figs. 45, 46, and 52). Internally, areolar openings round (Figs 54 and 55). Areolae extend around apices, but striae greatly reduced (Fig. 51). Longitudinal striae parallel over majority of valve but become slightly wavy at valve centre (Figs 42 and 45). External central area possessing an irregular grouping of small poroids of varying number (Figs 44, 47, and 52). Rows of areolae adjacent to either side of raphe terminate before distal raphe ending (Fig. 51). Internal longitudinal ribs robust, widen significantly but smoothly at central area before constricting at central nodule (Figs 53 and 55). Longitudinal ribs widen very abruptly near apices, then terminate bluntly at helictoglossa (Figs 42, 45, and 53). Longitudinal ribs fuse with the linear helictoglossa to form a wide and prominent porte-crayon structure (Fig. 54). External proximal raphe ends expanded into shallow crescent-moon shapes (Figs 51 and 52).

  • Author
    Graeff and Kociolek in Graeff et al. 2012
  • Length Range
    68-111 µm
  • Width
    17.5-21.0 µm
  • Striae in 10µm
    26–28 in the center, 28 at the ends

Cite This Page

Graeff, C. (2011). Frustulia rexii. In Diatoms of North America. Retrieved August 18, 2018, from https://diatoms.org/species/frustulia_rexii

Responses

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