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Craticula ambigua

D.G.Mann in Round, R.M.Crawford and D.G.Mann 1990      Category: Symmetrical biraphid
BASIONYM: Navicula ambigua Ehrenb. 1843
SYNONYM(S): Navicula cuspidata var. ambigua (Ehrenb.) Cleve 1894 

Craticula acidoclinata


Craticula buderi

LM scalebar = 10 µm = 40 pixels.


Contributor: Gina LaLiberte | Melissa Vaccarino | Steve Main - May 2015
Length Range: 38-75 µm
Width Range: 12-19 µm
Striae in 10 µm: 13-21 in the valve center, 17-21 at the ends


There are three valve types found for this taxon: vegetative, “heribaudii”, and craticula forms. The three forms are produced as a cellular strategy for suriving inimical conditions such as desiccation (Schmid 1979). Two craticula are formed within the vegetative frustule and subsequently the “heribaudii” cell is formed within the craticula. The heribaudii cell usually has different ornamentation compared to vegetative cell.

Valves are lanceolate, with protracted rostrate ends. The axial area is narrow and linear. The central area is only very slightly enlarged around the center. The raphe is filiform. The proximal raphe ends are slightly expanded. Striae are slightly radiate, becoming convergent at the ends. Striae may be slightly denser on one side of the valve as compared to the other side. Stria density increases as the size range decreases in this taxon.

In Europe, a greater range in size is reported (length 42-95 µm, breadth 13-24 µm, and striae count 15-18 in 10 µm) (Lange-Bertalot 2001).

Original Description

Basionym: Navicula ambigua
Author: Ehrenb. 1843
Length Range: µm
Striae in 10 µm:

Original Description

N. ambigua, testula a dorso lineari-oblonga utroque apice constricto brevi tenui obtuso. Icon! Priori similis; an pulli Pinnulariae dicephalae?

Original Images

Cite This Page:
LaLiberte, G., Vaccarino, M., and Main, S. (2015). Craticula ambigua. In Diatoms of the United States. Retrieved May 23, 2018, from

Species: Craticula ambigua

Contributor: Gina LaLiberte | Melissa Vaccarino | Steve Main

Reviewer: Rex Lowe


Ehrenberg, C.G. (1843). Verbreitung und Einfluß des mikroskopischen Lebens in Süd- und Nord-Amerika. Abhandlungen der Königlichen Akademie der Wissenschaften zu Berlin, 1841: 291-445, 4 Tafel.

Lange-Bertalot, H. (2001). Navicula sensu stricto, 10 genera separated from Navicula sensu lato, Frustulia. Diatoms of Europe 2: 1-526.

Links & ID's

Index Nominum Algarum (INA)

Transfer INA

California Academy of Sciences (CAS)

Craticula ambigua CAS

NCBI Genbank Taxonomy

Navicula ambigua Ehrenberg NCBI

North American Diatom Ecological Database (NADED)

NADED ID: 21010

Autecology Discussion

Craticula ambigua has been documented in alkaline wetlands and streams of Iowa, including Wickiup Hills (near Cedar Rapids) and Dugout Creek (Dickinson County).


Valve view of living C. ambigua from the Winnebago River, Iowa.

Credit/Source: Stephen Main

Girdle view of living C. ambigua from the Winnebago River, Iowa.

Credit/Source: Stephen Main

Craticula and heribaudii internal valves (Iowa Lakeside Lab Diatom Herbarium L-U24 70).

Credit/Source: Stephen Main