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Pinnularia acrosphaeria

W.Sm. 1853      Category: Symmetrical biraphid

Peronia fibula


Pinnularia borealis

LM scalebar = 10 µm = 40 pixels.


Contributor: Loren Bahls - March 2014
Length Range: 53-83 µm
Width Range: 9.7-12.0 µm
Striae in 10 µm: 11-13


Valves are linear, with a slightly gibbous center and broadly rounded, slightly subcapitate apices. The axial area is linear and about one-third as wide as the valve. The central area is asymmetric and only a bit wider than the axial area. The surface of the valve of both axial and central areas are mottled. Outer fissure of the raphe is straight, while the inner fissure is curved forming a lateral raphe. The features of the raphe may be difficult to discern against the mottled surface of the valve. Proximal raphe ends are weakly expanded, deflected to one side, and closely spaced. Terminal raphe fissures are deflected to the primary valve side. The terminal raphe fissures are comma- or sickle-shaped. Striae are weakly radiate at the valve center and parallel throughout the rest of the valve.

Krammer (2000) recognizes several varieties of P. acrosphaeria and the nominate variety is treated here. The varieties are described from outside continental North America: P. acrosphaeria var. sandvicensis A. Schmidt is described from Hawaii, P. acrosphaeria var. parma Krammer is described from Java and P. acrosphaeria var. tumidula Krammer is described from Germany.

Original Description

Author: W.Sm. 1853
Length Range: µm
Striae in 10 µm:

Original Description

Original Images

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

Species: Pinnularia acrosphaeria

Contributor: Loren Bahls

Reviewer: Marina Potapova


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.

Smith, W. (1853). Synopsis of British Diatomaceae. John Van Voorst, London 1853. 89 pp., pls 1-31.

Links & ID's

Index Nominum Algarum (INA)

Original INA

California Academy of Sciences (CAS)

NCBI Genbank Taxonomy

Pinnularia acrosphaeria NCBI

North American Diatom Ecological Database (NADED)

NADED ID: 52148

Autecology Discussion

The specimens of P. acrosphaeria pictured on this web page are from a spring, a small lake, and a pond in western Montana. Kootenai Pond (photo below) has a pH of 7.78 and a specific conductance of 139 µS/cm. Krammer (2002) reports this species as mainly tropical in distribution, but also widespread in temperate regions of the northern hemisphere, where it is epipelic in waters with average electrolyte content and circumneutral pH.


Kootenai Pond, Glacier National Park, Montana: home of Pinnularia acrosphaeria.

Credit/Source: Loren Bahls

Mud Lake, Bob Marshall Wilderness, Montana: home of Pinnularia acrosphaeria.

Credit/Source: John Pierce