• Category
  • Length Range
    64-133 µm
  • Width Range
    45-67 µm
  • Striae in 10 µm
  • Reported As
    Cymatopleura elliptica ((Bréb.) W.Sm.1851)



Valves are elliptic to lanceolate and symmetric about the apical and transapical axes with broadly rounded to slightly apiculate ends. Valves are roughly 1.5-2 times longer than they are wide. Along the margin of the valve, the alar canals are visible in LM. Fibula density is 3-4 in 10 μm. In SEM, striae appear radiate and convergent at the apices and transition to parallel toward the center of the valve. Striae are uniseriate and formed by fine areolae which become more dense toward the valve margin. Porcae are visible as transapical undulations across the valve face. Valves typically have nine porcae, up to eleven in larger valves. The raphe ends curve to the same side and are slightly enlarged.

This taxon was first described as Navicula undulata Ehrenb.1838. Later, Ehrenberg (1849) described S. undulata Ehrenb. 1845, without acknowledgment of the 1838 publication. Still later, Ehrenberg (1849) made the combination Surirella undulata (Ehrenb.) Ehrenb. 1849. Resolving if these taxa are of the same type or distinct entities needs to be investigated.

For many practitioners, this taxon is recognized and well-known as Cymatopleura elliptica (Bréb. ex Kütz.) W. Sm. 1851. However, C. elliptica is a later, subjective synonym (not of the same type).

Recent investigation into the phylogeny of the group (Ruck et al. 2016) supports a shared derived character, or synapomorphy, between Cymatopleura and Surirella. Simple portulae are found in both genera. These portulae form a cellular communication between the raphe canal and cell interior through fibulae. Because of this synapomorphy, Ruck et al. (2016) proposed a change in nomenclature to reflect evolutionary relationships. As a result, Cymatopleura taxa are now considered within Surirella.

This taxon also shares characteristics of the Surirella Pinnatae group by its isopolar valves and the marginal location of the raphe directly on the valve mantle (Jahn et al. 2017).


Surirella undulata was found in a benthic dredge sample and two separate gravity core samples from West Lake Okoboji, Dickinson County, Iowa and a planktonic sample from Beck’s Canal, Dickinson County, Iowa. The specimens found in West Lake Okoboji were found in pH 8.0-8.7.

20180522 111109
Credit: Katie Johnson
Gravity core from West Lake Okoboji, Iowa

Original Description

  • Basionym
    Navicula undulata
  • Author
    Ehrenb. 1838
  • Length Range
    125 µm
  • Width
    83 µm

Original Images

Navicula Undulata Ehrenb Orig Illus 1
Navicula Undulata Ehrenb Orig Illus 2
Navicula Undulata Ehrenb Orig Desc 1

Cite This Page

Hatcher, K. (2018). Surirella undulata. In Diatoms of North America. Retrieved June 20, 2024, from https://diatoms.org/species/surirella-undulata


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