Cymbopleura fluminea

(R.M.Patrick and Freese) Lange-Bert. and Krammer 2003      Category: Asymmetrical biraphid
BASIONYM: Cymbella fluminea R.M.Patrick and Freese 1961

REPORTED AS: Cymbopleura fluminea (Lange-Bertalot and Genkal 1999, p. 38, figs 56: 14-16) | Cymbella naviculiformis var. linearis (Foged 1981, p. 73, plate L, fig. 8) | Cymbopleura linearis (Krammer 2003, p. 58, figs 80: 1-11, 89: 1-11) 

Cymbopleura florentina


Cymbopleura frequens

LM scalebar = 10 µm = 80 pixels.


Contributor: Loren Bahls | Dan Bogan | Marina Potapova - September 2015
Length Range: 32-43 µm
Width Range: 8.3-9.1 µm
Striae in 10 µm: 14-18


Valves are linear-lanceolate and slightly dorsiventral, with broadly rostrate to capitate apices. Dorsal margins are slightly convex; ventral margins are nearly straight. The axial area, near the median line of the valve, is narrow at the valve ends and widens gradually to merge with a rounded central area of variable size. The central area ranges in size from about one-fifth to four-fifths of the valve width. The raphe is lateral, becoming filiform to reverse-lateral at the proximal ends. The proximal ends are weakly expanded and deflected towards the ventral margin. Terminal raphe fissures are deflected dorsally. Striae are radiate, more widely spaced near the valve center, and very finely punctate. Areolae are difficult to resolve in LM.

This taxon displays considerable variation within a population in length to width ratio, shape of the ends, width of the axial area and width of the central area.

To prepare this taxon page, we compared populations in British Columbia, Saskatchewan, the north slope of Alaska, and Swedish Lapland, along with the iconotype image of Cymbella naviculiformis var. linearis Foged (=Cymbopleura linearis (Foged) Krammer). We conclude that C. linearis is a later, subjective synonym for C. fluminea Patrick and Freese.

Original Description

Basionym: Cymbella fluminea
Author: R.M.Patrick and Freese 1961
Length Range: 34.0-40.0 µm
Width Range: 6.0-8.0 µm
Striae in 10 µm: 12-14 middle/dorsal, 14-15 middle/ventral, up to 18 at the apices (dorsal and ventral)

Original Description

Valve with median raphe, but one margin is convex and the other is straight. Apices broadly rostrate. Axial area narrow, slightly widened into the central area. Central area small, linear. No isolated punctum or stigma present. Striae finely punctate, radiate. Striae 12-14 in 10 µ in the middle part of dorsal margin, 14-15 in 10 µ in middle part of ventral margin. On both sides of the raphe the striae to 18 in 10 µ at the apices. Length 34-40 µ. Breadth 6-8 µ.

Original Images

Cite This Page:
Bahls, L., Bogan, D., and Potapova, M. (2015). Cymbopleura fluminea. In Diatoms of the United States. Retrieved April 22, 2018, from

Species: Cymbopleura fluminea

Contributor: Loren Bahls | Dan Bogan | Marina Potapova

Reviewer: Teofil Nakov


Foged, N. (1981). Diatoms in Alaska. Bibliotheca Phycologica, Band 53, J. Cramer, Vaduz, 317 pp.

Krammer, K. (2003). Cymbopleura, Delicata, Navicymbula, Gomphocymbellopsis, Afrocymbella. Diatoms of Europe. Diatoms of the European Inland Waters and Comparable Habitats 4: 1-530.

Lange-Bertalot, H. and Genkal, S.I. (1999). Diatoms from Siberia I. Islands in the Arctic Ocean (Yugorsky-Shar Strait). Iconographia Diatomologica 6: 1-292.

Patrick, R.M. and Freese, L.R. (1961). Diatoms (Bacillariophyceae) from Northern Alaska. Proceedings of the Academy of Natural Sciences of Philadelphia 112(6):129-293.

Links & ID's

Index Nominum Algarum (INA)

Transfer INA

California Academy of Sciences (CAS)

Cymbopleura fluminea CAS

North American Diatom Ecological Database (NADED)


Autecology Discussion

Patrick and Freese (1961) described conditions at the type locality as follows: “seepage over silt-gravel surface”, pH 6.7, temperature 18C, alkalinity 16 ppm (as CaCO3), hardness 30 ppm (as CaCO3), chloride 25 ppm, total iron (Fe) 0.07 ppm. Krammer (2003) reports both C. fluminea and C. linearis from oligotrophic waters with low electrolyte content. Besides several waters in Alaska, this species has also been reported from the subarctic region of Siberia (Lange-Bertalot and Genkal 1999), from Finnish and Swedish Lapland (Krammer 2003), and from a wet grassy meadow in northern Saskatchewan (photo below).


Wet grassy meadow near the Clearwater River in northern Saskatchewan, Canada: home of Cymbopleura fluminea.

Credit/Source: Beverly Boynton, Adventurers and Scientists for Conservation.