• Category
  • Length Range
    13-55 µm
  • Width Range
    5-9 µm
  • Striae in 10 µm
  • Synonyms
    Fragilaria leptostauron var. rhomboides (Grunow) Hust. 1931
    Staurosirella leptostauron var. rhomboides (Grunow) Andresen, Stoermer and Kreis 2000



Valves are rhomboid and slightly heteropolar. Valves with rounded ends. The central area is broad. The valve face is slightly to clearly undulate due to raised costae. The valve face/mantle junction forms a sharp angle. The abvalvar edge of the mantle is parallel to the valve face/mantle junction. In girdle view, frustules are rectangular. Cells form short ribbon-like colonies, joined by linking spines. The axial area is lanceolate. Striae are distinct, composed of lineolae. Lineolae are greatest in length midway between the sternum and valve mantle, 6-9 in 10 µm. Lineolae bear finely branched volae. Striae are radiate and extend continuously onto the valve mantle. Costae are as broad as the striae. Spines are flat, spatulate bearing short ligulae on the side. Spines are present along the valve face edge, except at the apices, and are located on the costae between striae. Well-developed, ocellulimbus type, apical pore fields with round poroids are present. Apical pore field at headpole less developed than that of footpole. Pore fields are located at the junction between the valve face/mantle. Rimoportulae are absent. Copulae, or girdle bands, are open and do not bear perforations. Valvocopulae are wider than other girdle elements. Cells form colonies attached to the substratum by a mucilage pad.


Cells form ribbon-like colonies with linking spines, attached by mucilage pads to the substrate.

Original Description

  • Basionym
    Fragilaria harrisonii var. rhomboides
  • Author
    Grunow 1862

Original Images

S Rhomboides Iconotype
S Rhomboides Original Description

Cite This Page

Morales, E. (2011). Staurosirella rhomboides. In Diatoms of North America. Retrieved June 22, 2018, from https://diatoms.org/species/staurosirella_rhomboides


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