• Category
  • Diameter
    7.8-15.1 µm
  • Striae in 10 µm
    15-16 based on chord count, 12-15 based on circumferential density



Valves are discoid, with a flat valve face. Striae are fine and punctate. Striae are radiate, bundled into fascicles and uniseriate in the center becoming biseriate near the margin. Fascicles originate from a central annulus and number 15-16 in 10 µm (based on chord count), 12-15 based on circumferential density. Fascicles are branching in some specimens. Areolae are fine, occurring 16-17 in 10 µm, and are visible only in larger specimens. Short, spatulate spines are present near the margin on every interfasicle. Usually one central fultoportula is present, but occasionally two fultoportulae are present.

The location of the fultoportulae is variable, according to Houk et al. (2014) and may be located anywhere from near the central annulus to near the valve margin.


Cyclostephanos invisitatus is planktonic and regarded as an indicator of eutrophic conditions in rivers (Edlund et al. 2009) and shallow lakes (Yang et al. 2005). Observed in all of the Laurentian Great Lakes, Reavie and Kireta (2015) found C. invisitatus to have a high total phosphorus optimum and most common in Lake Erie. Tibby and Reed (2004) found C. invisitatus to be more abundant in Iow salinity waters. In addition to observing a low conductivity optimum for C. invisitatus, Reavie & Smol (1998) sampled C. invisitatus from the epilithon, epiphyton, and the plankton of the St. Lawrence River.

Cyclostephanos Invisitatus
Credit: USGS BioData
Distribution of Cyclostephanos invisitatus in rivers of the continental U.S. based on the National Water Quality Assessment program. Retrieved 03 June 2015.

Original Description

Valves circular, diameter 9.2-11.4 µ; striae finely punctate, 16/10 µ; short submarginal recurved spines in indistinct hyaline interspaces; center of valve finely punctate, irregular.

  • Basionym
    Stephanodiscus invisitatus
  • Author
    M.H.Hohn and Hellermann 1963
  • Length Range
    9.2-11.4 µm
  • Striae in 10µm

Original Images

Stinvisitatus Original Images
Stinvisitatus Original Text

Citations & Links



Cite This Page

Burge, D., Edlund, M. (2015). Cyclostephanos invisitatus. In Diatoms of North America. Retrieved July 24, 2024, from https://diatoms.org/species/cyclostephanos_invisitatus


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