• Category
  • Length Range
    27.3-40.7 µm
  • Width Range
    4.3-5.3 µm
  • Striae in 10 µm
  • Reported As
    Cymbella lunata (Patrick and Reimer 1975, p. 46, plate 7, figs. 11-14)
    Cymbella gracilis (Krammer and Lange-Bertalot 1986, p. 308, fig. 120: 10-14)



Valves are lunate, or crescent shaped, with rounded apices. The dorsal margin is moderately arched. The ventral margin is concave. The axial area is narrow. The central area is small and asymmetric, formed by a slight shortening of the median dorsal stria. Proximal raphe ends are deflected to the dorsal side and terminate in inconspicuous central pores. Distal raphe fissures are long and curved ventrally. Striae on the dorsal side are radiate and more widely separated at the valve center than they are near the apices. The median dorsal stria may have a single isolated areola near the central valve. Striae are shorter on the ventral side and more or less parallel throughout. Areolae in the striae are very fine and number about 40 in 10 µm.


The specimens of E. lunatum shown on this web page were collected from wetland habitats on the tundra in Nunavut, Canada (photos below). These wetlands have circumneutral pH, low conductivity, and low concentrations of bioavailable nutrients. This species was described from material collected in Scotland and is widespread in suitable habitats (Krammer 1997).

Sample 685701  Wet Hummocks Near  Baillie  River
Credit: Beverly Boynton, Adventurers and Scientists for Conservation
Wet hummocks near Baillie River, Nunavut, Canada: home of Encyonema paucistriatum
Sample 686301  Wetland Near  Back  River
Credit: Beverly Boynton, Adventurers and Scientists for Conservation
Wetland near Back River, Nunavut, Canada: home of Encyonema lunatum

Original Description

  • Author
    W.Sm. in Grev. 1855

Original Images

Cymbella lunata orig illus 2
Cymbella lunata orig descr2

Cite This Page

Bahls, L. (2016). Encyonema lunatum. In Diatoms of North America. Retrieved July 21, 2018, from https://diatoms.org/species/encyonema_lunatum


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