• Category
  • Length Range
    5-26 µm
  • Width Range
    4-5.5 µm
  • Striae in 10 µm
  • Synonyms
    Staurosira venter (Ehrenb.) Cleve and J.D.Möller 1879
    Staurosira construens f. venter (Ehrenb.) Bukht. 1995
    Fragilaria construens var. venter (Ehrenb.) Grunow 1881



Valves are lanceolate with rostrate ends in larger specimens and elliptical with broadly rounded ends in smaller valves, 4-5.5 µm wide and 5-26 µm long. The valve face is flat, or slightly undulate due to raised costae. The valve face/mantle junction forms a sharp angle. In girdle view, frustules are rectangular and form ribbon-like colonies joined by linking spines. One cell within a colony is attached to the substratum by a frustule attached by a mucilage pad, or cells may be planktonic. The axial area is narrowly to widely lanceolate. The striae are distinct, alternate, and composed of oval areolae decreasing in size from the valve face/mantle edge to both the central sternum and the valve mantle; 12-16 in 10 µm. Lineolae bear finely branched volae. Striae vary from parallel to radiate in the central area to radiate toward the valve ends. Striae extend nearly to the mantle edge (abvalvar edge) in smaller specimens. The costae are broad. Spines are spatulate, hollow and some possess terminal digitations that connect to neighboring valve lineolae. Spines are present along the valve face edge, except at the apices, and always located on the costae between striae. Well-developed, ocellulimbus type, apical pore fields with round poroids are present. Apical pore fields are located on the junction between valve mantle/mantle. Rimoportula are absent. Scab-like deposits are present in some specimens on the abvalvar edge of the mantle near the valve apices. Copulae (girdle bands) are open and lack perforations. Valvocopulae are wider than copulae.

Morphological variability of specimens within single samples is common in S. construens var. venter, as with other varieties. This variability is not only related to size diminution during asexual reproduction, which mainly affects valve outline and striae orientation, but is also due to differences in shape of areolae, length and thickness of striae and degree of development of apical pore fields. For example, Morales (2001) and Morales et al. (2001) reported extensive morphological variability in valve outline and striation pattern and density in a single lake population from Connecticut.

Note that the name of this taxon will be updated, following upcoming revisions. - S. Spaulding (May 10, 2024)


This taxon is widely distributed and tolerant of a range of conditions. Cells may benthic and attach to substrate by mucilage pads. Alternatively, cells may be planktonic within colonies linked by spines.

Original Description

  • Basionym
    Fragilaria venter
  • Author
    Ehrenb. 1854

Original Images

S Construens Ventor Iconotype

Cite This Page

Morales, E. (2010). Staurosira construens var. venter. In Diatoms of North America. Retrieved July 15, 2024, from https://diatoms.org/species/staurosira_construens_var._venter


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