• Category
  • Length Range
    6–30 µm
  • Width Range
    4-5 µm
  • Striae in 10 µm
  • Reported As
    Synedra socia (Patrick and Reimer 1966)



Valves are linear and narrow, 4-5 µm wide and 14-31 µm long. Valves with rostrate to subcapitate ends. The central margin is unilaterally expanded. Valve face 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. The colonies are attached to the substratum at one end, by a frustule attached by a mucilage pad, or planktonic. The central area clear across the valve in large specimens or a one-sided clear area in medium-sized to small specimens. Ghost striae may be present in the central area devoid of ornamentation. The striae are distinct and composed of long lineolae giving the impression of thick striae, 14-16 in 10 µm, and the costae are broad. The lineolae bear finely branched volae. The striae are mostly parallel, to slightly radiate toward the valve ends. Striae alternate. Striae extend onto the valve mantle, interrupted by spines at the valve face/mantle junction. The spines are spatulate, fine and delicate. They are present along the valve face edge, except at the apices. The spines may be absent, especially in small specimens. Well-developed, ocellulimbus type, apical pore fields with round poroids are present. A single rimoportula is present on each valve, aligned with the first stria at the valve face apex. The rimoportula is located on, or just off the central sternum, and is parallel or slightly inclined in a counterclockwise fashion with respect to the transapical axis. Scab-like structures, or blisters, are present along the abvalvar portion of the mantle. Copulae, or girdle bands, bear small, unoccluded perforations located just beneath the previous girdle element’s abvalvar edge. Plastids are unknown.

Researchers in North America may have also referred this taxon (especially individual valves) to Synedra socia Wallace based on treatment of this taxon in Patrick and Reimer (1966). Additional study is needed to determine the relationship of S. socia to F. vaucheriae. Several described varieties of Fragilaria capucina with thickened and expanded central areas also deserve closer scrutiny.


Benthic, forming palisade colonies attached to substratum by one end, or attached singly to substratum by a mucilage pad.

Original Description

Frustulis aut solitariis aut fasciculatis, minutissimus, linearibus, utrinque obtusis, altero latere apicem versus subattenuatis et rotundato-obtusis, viridi-lutescentibus et maculatis.

  • Basionym
    Exilaria vaucheriae
  • Author
    Kütz. 1833

Original Images

Fragilaria vaucheriae orig illus
Fragilaria Vaucheriae Original Description

EMAP Assessment

EMAP Distribution

Fragilaria Vaucheriae 5 Copy
Map 3

Response Plots

Fragilaria Vaucheriae Copy

Cite This Page

Morales, E. (2010). Fragilaria vaucheriae. In Diatoms of North America. Retrieved June 17, 2018, from https://diatoms.org/species/fragilaria_vaucheriae


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