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Pinnularia gigas

Ehrenb. 1843      Category: Symmetrical biraphid

REPORTED AS: Pinnularia dactylus (Patrick and Reimer 1966, p. 632, plate 62, fig. 4) | Pinnularia dactylus (Krammer and Lange-Bertalot 1986, p. 430, fig. 198: 1) 

Pinnularia divergentissima


Pinnularia lata

LM scalebar = 10 µm = 20 pixels.


Contributor: Loren Bahls - March 2014
Length Range: 173-297 µm
Width Range: 39.3-64.0 µm
Striae in 10 µm: 4-5


Valves are large and linear-elliptic with slightly convex margins and rounded apices. The post-initial valves are tumid in the center. The central area is asymmetric and rounded. The raphe is distinctly lateral and complex (a raphe with an extremely curved outer fissure). Proximal raphe ends are deflected to one side and terminate in small pores. Terminal raphe fissures are S-shaped, or bayonet-shaped depending on the depth of focus. Striae are radiate at the valve center, becoming parallel near the apices. Striae are crossed by a broad longitudinal line. The proximal edge of this band is distinct.

Original Description

Author: Ehrenb. 1843
Length Range: µm
Striae in 10 µm:

Original Description

Original Images

Cite This Page:
Bahls, L. (2014). Pinnularia gigas. In Diatoms of the United States. Retrieved May 23, 2018, from

Species: Pinnularia gigas

Contributor: Loren Bahls

Reviewer: Marina Potapova


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.

Krammer, K. (1992). Die Gattung Pinnularia in Bayern. Hoppea 52: 1-308.

Krammer, K. (2000). The genus Pinnularia. The Diatoms of Europe. Diatoms of Inland Waters and Comparable Habitats 1: 1-703.

Krammer, K. and Lange-Bertalot, H. (1986). Bacillariophyceae. 1. Teil: Naviculaceae. In: Ettl, H., J. Gerloff, H. Heynig and D. Mollenhauer (eds.) Süsswasserflora von Mitteleuropa, Band 2/1. Gustav Fisher Verlag, Jena. 876 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.

Links & ID's

Index Nominum Algarum (INA)

Original INA

California Academy of Sciences (CAS)

Pinnularia gigas CAS

North American Diatom Ecological Database (NADED)


Autecology Discussion

The specimens of P. gigas pictured on this website are from two small ponds and a fen in Glacier National Park, Montana. In these waters, pH ranges from 6.02 to 7.34 and specific conductance from 31 to 71 µS/cm. Krammer (2000) reports this species from nordic-alpine regions in oligotrophic waters with low electrolyte content and low pH.


Atlantic Pond, Glacier National Park, Montana: home of Pinnularia gigas.

Credit/Source: Loren Bahls