• Category
  • Diameter
    5-10 µm
  • Synonyms
    Rhizosolenia eriensis H.L.Sm.



Frustules are thinly silicified. In most preparations, the frustules are positioned so that they lie in girdle view. The valve is obliquely conical, and has a long, tubular process that extends from each valve. The process is eccentric in its position on the valve face. Together, the valve and tubular process are termed a calyptra (Schröder 1911). The valve face is ornamented with radiate poroids, or ribs (Rott et al. 2006). In LM, it is difficult to determine if the process includes a seta (a delicate extension originating from the tip of the process).

Girdle bands are composed of scale-like half bands, joined so that they form a zig-zag pattern between the columns, along the apical plane. The meeting point of the half bands meet is termed the “imbrication line”. This line may be shifted to one side, dependent upon the valve orientation. Girdle bands number 2-4 in 10 µm. Frustules are joined in chains, with each process positioned along the apical edge of the opposing frustule.

This species forms true resting spores, which are often well preserved in sediments (Edlund and Stoermer 1993). The spores have a primary valve that is domed, with spines near the valve margin. The secondary valve is concentrically undulate, with a domed center. The secondary valve of some specimens may possess small spines.


This taxon is planktonic and primarily grows in lakes. Most of the specimens shown here are from Lake Superior. It is likely to be widely distributed, but it is often overlooked because the lightly silicified frustules are easily destroyed in processing.

We also observed this taxon in collections from a fish hatchery pond (collected by M. Winkler on 28 July 1981) and in West Lake Okoboji (collected by J. Hungerford on 30 July 1970), in Dickinson County, Iowa. In both the Lake Superior and Lake Okoboji samples, there were more than one species of Urosolenia, the first was probably U. gracilis. We expect the second taxon taxon may be undescibed. This taxon was distinguished by longer processes and girdle bands that were less curved.

Urosolenia Eriensis Lm3
Credit: Sampled by Mark Edlund
Two frustules in girdle view linked in a chain. Burn mount of plankton sample from Lake Superior.
Urosolenia Eriensis Burn Mount West Okoboji 1970
Credit: Image by Sylvia Lee
Burn mount of a plankton tow sample from West Lake Okoboji, Dickinson Country, Iowa sampled by J. Hungerford on July 30, 1970. Reimer Herbarium slide L-5-33.
Rott Et Al 2006 Urosolenia 7
Fig. 1 from Rott et al. 2006 showing morphological features of Urosolenia.

Original Description

Frustules small, compressed, somewhat flattened; not rigidly siliceous; six to twelve times as long as broad; length .003 to .006. Annuli on the dry frustules conspicuous, apparently interrupted in the middle, and alternate; obscure in fluid or balsam. Frustules finely striated. Bristles nearly as long as the frustules, and, with the calyptra, excentric (sic), lying nearly in a line with one margin of the frustule when the flat side is in view. Chicago water-supply; very abundant at certain seasons, and very rare at others. Originally noted in Lake Erie, at Cleveland, O. (Briggs 1872 page 44).

  • Basionym
    Rhizosolenia eriensis
  • Author
    H.L.Sm. 1872
  • Length Range
    3-6 µm

Original Images

Urosolenia Eriensis Orig Illus2
Urosolenia Eriensis Orig Desc

Cite This Page

Silvester, E., Lee, S. (2019). Urosolenia eriensis. In Diatoms of North America. Retrieved June 21, 2024, from https://diatoms.org/species/urosolenia-eriensis


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