• Category
  • Length Range
    8-50 µm
  • Width Range
    3-6 µm
  • Striae in 10 µm
    11-12 in the center valve, 13-15 at the ends
  • Reported As
    Rhoicosphenia abbreviata ((Agardh) Lange-Bertalot 1980)

Identification

Description

Frustules are clavate and strongly flexed in girdle view. Valves are heteropolar in valve view, linear-lanceolate with protracted apices in larger specimens and rounded apices in smaller specimens. Frustules are heterovalvate; one valve is concave with long raphe branches (raphe valve), one valve convex with shortened raphe branches (reduced raphe valve). On the raphe valve, the raphe is filiform. The proximal raphe ends are dilated externally and crook-shaped internally in same direction. The distal raphe ends curve in same direction externally. Internally the raphe ends terminate in in helictoglossae. The axial area is narrow, widening to form a small, ovate central area. Striae are parallel to radiate in the center of the valve and radiate at the apices. The striae are composed of round to lineate areolae, 40 in 10 μm. On the reduced raphe valve, raphe branches are 3–5 μm long at head pole, and do not extend beyond the pseudoseptum. Raphe branches are 5–7 μm long at foot pole. The external proximal ends are not expanded. The internal proximal ends are crook-shaped in same direction. The distal ends are not inflated externally and terminate in helictoglossae internally. Striae are parallel throughout. Both valves with pseudosepta at each apex, 3–8 μm long. Both valves with apical pore field at the foot pole, in which porelli number 4 per 1 μm. Girdle bands are open.

Autecology

Original Description

Frustules clavate and strongly flexed in girdle view. Valves heteropolar in valve view, linear-lanceolate with protracted apices in larger specimens and rounded apices in smaller specimens, 8–50 μm long, 3–6 μm wide. Frustules heterovalvate, one valve concave with long raphe branches (R-valve), one valve convex with shortened raphe branches (D-valve). R-valve: raphe filiform, proximal raphe ends dilated externally, crook-shaped internally in same direction, distal raphe ends curved in same direction externally ending in helictoglossae internally. Axial area narrow, widening at small ovate central area. Striae parallel to radiate in center of the valve and radiate at apices, 11–12 striae in 10 μm at center of valve, 13–15 striae in 10 μm at apices, composed of round to lineolate areolae, 40 in 10 μm. D-valve: raphe branches 3–5 μm long at head pole, not extending beyond pseudoseptum, and 5–7 μm long at foot pole, external proximal ends not expanded, internal proximal ends crook-shaped in same direction and distal ends not inflated externally, terminate in helictoglossae internally. Striae parallel throughout, 12–14 striae in 10 μm at center of valve, 13–16 striae in 10 μm at apices, composed of round to lineolate areolae. Both valves with pseudosepta at each apex, 3–8 μm long. Both valves with apical pore field at foot pole, porelli 4 per 1 μm. Girdle bands open.

  • Author
    Thomas and Kociolek 2015
  • Length Range
    8-50 µm
  • Width
    3-6 µm
  • Striae in 10µm
    11-12 in the center valve, 13-15 at the ends

Original Images

R Californica  Holotype

Cite This Page

Thomas, E. (2015). Rhoicosphenia californica. In Diatoms of North America. Retrieved August 18, 2018, from https://diatoms.org/species/rhoicosphenia_californica

Responses

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