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Cymbella mexicana

(Ehrenb.) Cleve 1894      Category: Asymmetrical biraphid
BASIONYM: Cocconema mexicanum Ehrenb. 1844

Cymbella maggiana


Cymbella mexicana var. kamtschatica

LM scalebar = 10 µm = 20 pixels.


Contributor: Briana Johnson - June 2011
Length Range: 80-155 µm
Width Range: 26-33 µm
Striae in 10 µm: 6-8 in the central valve, 7-10 at the ends


Valves are moderately to strongly dorsi-ventral, with rounded apices. The outline of valve is cymbelliform-lanceolate to broadly semi-lanceolate. The dorsal margin is strongly arched, whereas the ventral margin is slightly concave. The central portion of the ventral margin is slightly convex. The small central area is circular to oval in shape. A single, large stigma is present between the proximal raphe ends. The proximal raphe ends have distinct central pores that curve to the ventral margin. The raphe is lateral near the middle of the valve, becoming thread-like near the distal end. The terminal raphe fissures are dorsally deflected nearly 90º. Apical pore fields are present at both apices. Striae are radiate near the center of the valve, becoming parallel towards the ends. The dorsal and ventral striae in the central portion of the valve are variable in length (often 3 or more striae are half the length of the other striae). The areolae appear to be rectangular to circular in shape. Areolae adjacent to the raphe are elongated into a triangular shape. Areolae number 10-12 in 10 µm, occasionally up to 14 in 10 µm.

Note that Cymbella janischii was described as a distinct species by De Toni in 1891. Later, Patrick & Reimer (1975) considered it a variety of Cymbella mexicana. They are treated as two species in this database.

Original Description

Basionym: Cocconema mexicanum
Author: Ehrenb. 1844
Length Range: µm
Striae in 10 µm:

Original Description

Cocconema mexicanum, testula majore striata crassa lunata, ventre leviter lumido, cornubus parum elongatis obtusis, striis in 1/90”’ 18 distincte et eleganter granulosis. Long. 1/18”’. Mexico.

Original Images

Cite This Page:
Johnson, B. (2011). Cymbella mexicana. In Diatoms of the United States. Retrieved May 20, 2018, from

Species: Cymbella mexicana

Contributor: Briana Johnson

Reviewer: Sarah Spaulding


Bahls, L. L. (2007). Cymbella janischii–Giant endemic diatom of the Pacific Northwest: morphology, ecology and distribution compared to Cymbella mexicana. Northwest Science 81 (4): 284-292.

Cleve, P.T. (1894). Synopsis of the Naviculoid Diatoms, Part I. Kongliga Svenska-Vetenskaps Akademiens Handlingar 26(2):1-194, 5 pls.

Edsall, T.A., Stoermer, E.F. and Kociolek, J.P. (1991). Periphyton accumulation at remote reefs and shoals in Lake Superior. Journal of Great Lakes Research 17(3).

Ehrenberg, C.G. (1844). Über einen deutlichen Einfluss des unsichtbar kleinen organischen Lebens als vulkanisch gefrittete Kieselmasse auf die Massenbildung von Bimstein, Tuff, Trafs, vulkanischem Conglomerat und auch auf das Muttergestein des nordasiatischen Marekanits. Bericht über die zur Bekanntmachung geeigneten Verhandlungen der Königlich-Preussischen Akademie der Wissenschaften zu Berlin 1844: 324-344.

Krammer, K. (1982). Valve morphology and taxonomy in the genus Cymbella C.A. Agardh. Morphology of Diatom Valves 11: 1-299.

Krammer, K. (1997). Die cymbelloiden Diatomeen. Eine Monographie der weltweit bekannten Taxa. Teil 1. Allgemeines und Encyonema. Bibliotheca Diatomologica 36: 1-382.

Patrick, R.M. and Reimer, C.W. (1975). The Diatoms of the United States, exclusive of Alaska and Hawaii, V. 2. Monographs of the Academy of Natural Sciences of Philadelphia 13.

Links & ID's

Index Nominum Algarum (INA)

Original INA

California Academy of Sciences (CAS)

Cymbella mexicana CAS

NCBI Genbank Taxonomy

Cymbella mexicana NCBI

North American Diatom Ecological Database (NADED)

NADED ID: 23078

Autecology Discussion

Cymbella mexicana secretes a mucilaginous stalk from either of two apical pore fields. Live cells contain one large, central golden-brown chloroplast that stretches the breadth of the valve and ~ ½ the distance to each end. For this study, C. mexicana was was found in a number of samples, including shallow water in the epilithon of Beck’s Canal, Dickinson County, Iowa (pH 6.85, 16ºC, 6.8 mg/L DO, 381 µS/cm), a boat ramp in Lazy Lagoon, Dickinson County, Iowa (pH 8.1, 16.7ºC, 6.7 mg/L DO, 449 µS/cm), and Grove Lake, Antelope County, Nebraska (pH 9, 20.7ºC, 7.1 mg/L DO, 293 µS/cm). The Iowa Lakeside Lab Herbarium contains C. mexicana specimens from epiphytic, epipsammic, and epilithic samples of East Lake Okoboji, West Lake Okoboji, Gar Lake, Beck’s Canal, and Milford Creek, all within Dickinson County, Iowa.

Other confirmed distributional records in the United States include: Montana, North Dakota, South Dakota, Wyoming, Idaho, Oregon, California (Bahls 2005), Alaska (Foged 1981), the Colorado River near Parker, Arizona (Krammer 2002), and Lake Superior (Edsall et al. 1991).

A confirmed C. mexicana fossil was reported from the Lower Klamath Lake, Oregon (Krammer 2002).


Cymbella mexicana, (live under 20x magnification) from Little Millers Bay, Dickinson Co., Iowa

Credit/Source: Mark Edlund

Cymbella mexicana, (live under 40x magnification) from Little Millers Bay, Dickinson Co., Iowa

Credit/Source: Mark Edlund

Cymbella mexicana sample location at Beck’s Canal, Dickinson Co., Iowa

Credit/Source: Lisa Allinger

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

Cymbella mexicana

EMAP Response Plots

Cymbella mexicana

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.