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Pinnularia polyonca

(Bréb.) W.Sm. 1856      Category: Symmetrical biraphid
BASIONYM: Navicula polyonca Bréb. in Kütz. 1849

Pinnularia parvulissima


Pinnularia rabenhorstii

LM scalebar = 10 µm = 40 pixels.


Contributor: Loren Bahls - March 2012
Length Range: 68-80 µm
Width Range: 8.9-10.3 µm
Striae in 10 µm: 10-12


Valves are rhombic-lanceolate with a triundulate outline, the middle expansion is wider than the distal ones. Apices are capitate and rounded. The axial area is very wide and lanceolate in shape. The central area is a transverse fascia. In some populations, there are one or two short striae on the secondary side of the fascia. The raphe is lateral. Proximal raphe ends are curved to the primary side. Terminal raphe fissures are shaped like question marks. Striae are very short and radiate in the middle, becoming longer and strongly convergent towards the apices.

With their shorter striae, less swollen middles, and broad axial areas with distinct markings, the specimens pictured above belong to P. polyonca var. stidolphii. Thanks to Paul Hamilton for this observation.

Original Description

Basionym: Navicula polyonca
Author: Bréb. in Kütz. 1849
Length Range: µm
Striae in 10 µm:

Original Description

Original Images

Cite This Page:
Bahls, L. (2012). Pinnularia polyonca. In Diatoms of the United States. Retrieved May 22, 2018, from

Species: Pinnularia polyonca

Contributor: Loren Bahls

Reviewer: Sarah Spaulding


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.

Kützing, F.T. (1849). Species Algarum. Lipsiae. F.A. Brockhaus, 922 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.

Smith, W. (1856). Synopsis of British Diatomaceae. John Van Voorst, London 1856. 2: 107pp., pls. 32-60, 61-62, A-E.

Links & ID's

Index Nominum Algarum (INA)

Transfer INA

California Academy of Sciences (CAS)

Pinnularia polyonca CAS

North American Diatom Ecological Database (NADED)

NADED ID: 52087

Autecology Discussion

Pinnularia polyonca has been found in two small lakes and a floating-mat fen in western Montana. All three sites have abundant vascular plant growth. The pH of these sites ranges from 6.73 to 7.41 and specific conductance ranges from 22 to 257 µS/cm.


Skinner Lake, Beaverhead National Forest, Montana: home of Pinnularia polyonca.

Credit/Source: Loren Bahls