• Category
  • Length Range
    17.6-21 µm
  • Width Range
    6.9-8.5 µm
  • Striae in 10 µm
    13.7-19.2
  • Reported As
    Fragilaria sp. 2 NAWQA EAM (NADED 34179)

Identification

Description

Valves are cruciform and strongly symmetrical. Valves abruptly narrow and extend more than the length of the swollen central area to capitate or subcapitate ends. Striae are alternate and slightly radial at the center to radial at the ends. The axial area is narrow and linear. Marginal spines are present and are particularly visible in girdle view. Spines are longer at the center of cells, resulting in gaps between adjacent cells which are visible in girdle view. Spines are spatulate. Lacks a central area, apical pore field, and rimoportula.

Frustules grow in short chains of a few cells. The colonies may be joined face to face, or joined at only one end of a frustule.

Autecology

This taxon was observed in the sediments of Lake Okeechobee, Florida (Stoermer et al. 1992). Frustules are joined in short chains of several cells. In many colonies, adjacent cells are separated near the apices.

16 57564
Credit: Gina LaLiberte
Separation between cells as seen in girdle view. Specimens from the holotype population. Academy of Natural Sciences GC 57564
23 57564
Credit: Gina LaLiberte
Separation between cells as seen in girdle view. Specimens from the holotype population. Academy of Natural Sciences GC57564

Original Description

DESCRIPTION: Frustules rectangular in girdle view, often arranged in chains (Figs 5, 6, 11) with the aid of spatulate solid spines (Figs 10, 11). Spines longer at the central area resulting in the separation of the apices of contiguous cells (Figs 5, 11). Valve surface flat (Figs 7, 8, 11). Valves swollen in the central area, elegantly cruciform (Figs 1 - 4, 7, 8), and very symmetrical in valve view (widest in the centre, same as valve width). Ends of the valve rounded or slightly capitate, 1.5 ± 1.8 μm wide. Pseudoraphe distinct with a linear and very narrow central sternum (Figs 1-4, 7, 8). Areolae vary from round along the apical axis to slightly linear along the valve margins, 6 in 1 μm. Striae alternate along the sternum and continue onto the valve mantle (Figs 7 ± 11). Apical pore fields absent or very reduced. Girdle bands open and valvocopulae narrow (Fig. 12). Rimoportulae not present (Figs 9, 11). Chloroplast plate-like and large. Valve length 18 ± 21 μm, width 7 ± 9 μm, and stria density 14 ± 19 per 10 μm.

  • Author
    Manoylov, E.Morales and Stoermer 2003
  • Length Range
    18-21 µm
  • Width
    7-9 µm
  • Striae in 10µm
    14-19

Original Images

Staurosira Stevensonii Original Images
Staurosira Stevensonii Original Description

Cite This Page

LaLiberte, G. (2015). Staurosira stevensonii. In Diatoms of North America. Retrieved July 21, 2018, from https://diatoms.org/species/staurosira_stevensonii

Responses

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