Meridion circulare var. constrictum

(Ralfs) Brun 1880      Category: Araphid
BASIONYM: Meridion constrictum Ralfs 1843

Meridion circulare


Meridion lineare

LM scalebar = 10 µm = 80 pixels.


Contributor: Natalie Hoidal - June 2013
Length Range: 12-55 µm
Width Range: 5-8 µm
Striae in 10 µm: 16-20


Frustules are linear-clavate. In valve view, the headpole is rostrate. A narrow sternum extends the length of the apical axis of the valve. Striae are grouped together, 1-6 between costae. Numerous costae are present, positioned along the transverse axis. In some specimens, costae are not visible near the footpole. A rimoportula is present near the headpole, and usually visible under the light microscope. Cells often grow in fan-shaped colonies. Internal valves are common in this taxon.

Original Description

Basionym: Meridion constrictum
Author: Ralfs 1843
Length Range: µm
Striae in 10 µm:

Original Description

M. constrctum. Lateral surfaces constricted below the apex, transversely striated : the ends of the striae forming puncta along the margins of the front view.

Original Images

Cite This Page:
Hoidal, N. (2013). Meridion circulare. In Diatoms of the United States. Retrieved April 22, 2018, from

Species: Meridion circulare

Contributor: Natalie Hoidal

Reviewer: Sam Rushforth


Brun, J. (1880). Diatomées des Alpes et du Jura et de la région Suisse et Française des Environs de Genève. Imprimerie Ch. Schuchardt, Genève. 146 pp.

Patrick, R.M. and Reimer, C.W. (1966). The Diatoms of the United States exclusive of Alaska and Hawaii, V. 1. Monographs of the Academy of Natural Sciences of Philadelphia 13.

Ralfs, J. (1843). On the British species of Meridion and Gomphonema. Annals and Magazine of Natural History 12: 457-467.

Rhode, K.M, Pappas, J.L. and Stoermer, E.F. (2001). Quantitative analysis of shape variation in type and modern populations of Meridion Ag. Journal of Phycology 37: 175-183.

Stancheva, R. (2006). Distribution of resting spores of Eunotia soleirolii and Meridion circulare var. constrictum (Bacillariophyta) in sediments of peat bogs from Mt. Central Sredna Gora, Bulgaria. In Ognjanova-Rumenova, N. and Manoylov, K. (eds.) Advances in Phycological Studies, Pensoft, Sofia and Moscow. 111-121 pp.

Williams, D.M. (1985). Morphology, taxonomy and inter-relationships of the ribbed araphid diatoms from the genera Diatoma and Meridion (Diatomaceae: Bacillariophyta). Bibliotheca Diatomologica 8: 1-228.

Links & ID's

Index Nominum Algarum (INA)

Original INA

California Academy of Sciences (CAS)

Meridion circulare var. constrictum CAS

North American Diatom Ecological Database (NADED)

NADED ID: 45002

Autecology Discussion

Meridion circulare var. constrictum was found in a prairie stream north of Iowa Lakeside Lab, Dickinson County, Iowa. Specimens from the Iowa Lakeside Lab Herbarium confirmed this taxon in soils, duffs from prairie swales, moss, a plankton tow from “No Name” creek in Dickinson County, the surface of a small puddle and in sand from the Little Sioux River.

This species has a fairly cosmopolitan distribution, but is most commonly found in streams and creeks. Williams (1985) described the taxon as being sited in Great Britain, France, Hungary, USA, New Zealand, France, and Lapland. As the cells divide, they form fan-like colonies growing on plants and rocks (Ralfs, 1843). Meridion circulare var. constrictum is less common than the nominate variety and considered to survive outside of permanent water bodies in locations such as puddles (Stancheva, 2006).


Live colony from Northern prairie stream at Iowa Lakeside Lab, Dickinson County, Iowa.

Credit/Source: Natalie Hoidal

Live colony from Northern prairie stream at Iowa Lakeside Lab, Dickinson County, Iowa

Credit/Source: Natalie Hoidal

EMAP Assessment

The Environmental Protection Agency (EPA) western Environmental Monitoring and Assessment Program (EMAP) study was completed during the years 2000-2004 (see citations at bottom of this page). Over 1200 streams and rivers in 12 western states (Arizona, California, Colorado, Idaho, Montana, Nevada, North Dakota, Oregon, South Dakota, Utah, Washington and Wyoming) were selected for sampling based on a stratified randomized design. This type of design insures that ecological resources are sampled in proportion to their actual geographical presence. Stratified randomized design also allows for estimates of stream length with a known confidence in several “condition classes” (good or least-disturbed, intermediately-disturbed, and poor or most-disturbed) for biotic condition, chemistry and habitat.

EMAP Distribution

Meridion circulare var. constrictum

EMAP Response Plots

Meridion circulare var. constrictum

EMAP citations

Results are published in:

Johnson, T., Hermann, K., Spaulding, S., Beyea, B., Theel, C., Sada, R., Bollman, W., Bowman, J., Larsen, A., Vining, K., Ostermiller, J., Petersen, D. Hargett, E. and Zumberge, J. (2009). An ecological assessment of USEPA Region 8 streams and rivers. U.S. Environmental Protection Agency Region 8 Report, 178 p.

Stoddard, J. L., Peck, D. V., Olsen, A. R., Larsen, D. P., Van Sickle, J., Hawkins, C. P., Hughes, R. M., Whittier, T. R., Lomnicky, G. A., Herlihy, A. T., Kaufman, P. R., Peterson, S. A., Ringold, P. L., Paulsen, S. G., and Blair, R. (2005). Environmental Monitoring and Assessment Program (EMAP) western streams and rivers statistical summary. U.S. Environmental Protection Agency Report 620/R-05/006, 1,762 p.

Stoddard, J. L., Peck, D. V., Paulsen, S. G., Van Sickle, J., Hawkins, C. P., Herlihy, A. T., Hughes, R. M., Kaufman, P. R., Larsen, D. P., Lomnicky, G. A., Olsen, A. R., Peterson, S. A., Ringold, P. L., and Whittier, T. R. (2005). An ecological assessment of western streams and rivers. U.S. Environmental Protection Agency Report 620/R-05/005, 49 p.