• Category
  • Length Range
    26.2-37.2 µm
  • Width Range
    9.0-11.6 µm
  • Striae in 10 µm
    12-14 in the valve center, up to 18 near the apices
  • Reported As
    Cymbopleura citriformis (Krammer 2003, p. 68, figs 97: 13-15, 98: 1-5)
    Cymbopleura designata (Lange-Bertalot and Genkal 1999, p. 226, figs 56: 17-19 INVALID NAME)
  • Genus Considered



Valves are broadly lanceolate and moderately dorsiventral with strongly arched dorsal and ventral margins. Apices are apiculate and extend laterally from the ends of the valve. The axial area is about 1/4 to 1/5 the valve width, curved, and narrower near the apices. The central area is slightly tumid and scarcely wider than the axial area. Raphe branches are weakly lateral near their centers and filiform towards the proximal and distal ends. Proximal raphe ends are slightly expanded and displaced ventrally. Distal raphe ends are comma-shaped and deflected dorsally. Striae are radiate throughout. Areolae in the striae number 26-30 in 10 µm.

The nomenclatural history of this taxon is convoluted. Krammer (1985) proposed that Cymbella leptoceros var. rostrata Hustedt is morphologically dissimilar to Cymbella leptoceros and should, therefore, be elevated to the rank of species, creating the new name and rank of Cymbella designata Krammer. Later, Lange-Bertalot and Genkal (1999) suggested that Cymbella designata belongs in Cymbopleura (p. 226, figs 56: 17-19) but they failed to formally transfer the species, so the name Cymbopleura designata is invalid.

In 2003, Krammer published the new species Cymbopleura citriformis, which appears to be conspecific with Cymbella designata. The type of the basionym Cymbella leptoceros var. rostrata Hustedt 1942, which is Cymbella designata, has nomenclatural priority.


Krammer (2002) reports Cymbella designata from sub-arctic and arctic sites with oligotrophic waters of low mineral content and notes records from north Sweden, north Finland, north Norway, north Russia, Spitsbergen, Greenland, and Alaska. The specimens shown here were collected from small circumneutral tundra lakes above the Arctic Circle in Nunavut, Canada. Cymbella designata (presented as Cymbopleura citriformis) was also reported as a fossil in sediment deposited at the bottom of a lake in north Germany (Krammer 2003).

Sample 6 3
Credit: Beverly Boynton, Adventurers and Scientists for Conservation.
Red Sand Lake, Nunavut, Canada.

Original Description

  • Basionym
    Cymbella leptoceros var. rostrata
  • Author
    Hust. 1942

Original Images

Cymbella leptoceros var. rostrata orig illus

Cite This Page

Bahls, L. (2015). Cymbella designata. In Diatoms of North America. Retrieved July 15, 2024, from https://diatoms.org/species/cymbopleura_citriformis


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