• Category
  • Length Range
    64-148 µm
  • Width Range
    2.8-7.9 µm
  • Synonyms
    Ceratoneis gracilis Bréb. ex Kütz. 1849
    Nitzschiella gracilis (Bréb. ex Kütz.) Rabenhorst 1864



Frustules are weakly silicified, shaped like a spindle, with linear margins. The frustule is twisted about the apical axis so that the valve and girdle bands spiral around the length of the cell. The valve is composed of two narrow strips of silica joined by fibulae (i.e., the valve consists only of the raphe system), about 20 fibulae in 10 µm. The apices are protracted and the apical ends appear subcapitate only from some angles because of the twisted valve construction (and lack of valve view or girdle view orientations). The apices or entire frustule often appear bent or broken, possibly due to processing.


This taxon is common in the plankton of large, slow moving rivers, particularly in the eastern rivers of Montana and midwest states. It is, however, greatly under reported because the lightly silicified valves are destroyed in most laboratory processing.

Christensen and Reimer (1968) reported the distribution of C. gracilis in the United States from the following localities: Patuxent River, Prince Georges County, Maryland (brackish water); Ottawa River, Allen County, Ohio (fresh water); Dugout Creek, Dickinson County, Iowa (fresh water). The authors noted that C. gracilis appears to tolerate both fresh and brackish conditions, and that total conductivity, concentration of sulfates, magnesium, calcium, or some combination of these chemical variables may be more critical to the growth and distribution of this diatom than chloride or sodium ions (Christensen and Reimer 1968). Additional records from Idaho, Montana, North Dakota, South Dakota, and Wyoming are found in Bahls (2009) and the Savannah River estuary (Manoylov and Dominy 2013).

Original Description

C. gracilis. Bréb. in litt. - C. linearis, elongata, apices versus attenuata, curvula vel sigmoides, obtisiuscula. - Long. 1/25'''. Lat. 1/500'''-1/450'''. - In aqua dulci circa Falaise, Galliae, detexit cl. De Brébission. (v.s.)

  • Basionym
    Ceratoneis gracilis
  • Author
    Bréb. ex. Kütz. 1849

Original Images

Ceratoneis gracilis orig desc

Citations & Links



Cite This Page

Meer, D., Lee, S. (2021). Cylindrotheca gracilis. In Diatoms of North America. Retrieved June 23, 2024, from https://diatoms.org/species/cylindrotheca-gracilis


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