Pinnularia nodosa var. percapitata

Krammer 2000      Category: Symmetrical biraphid

Pinnularia nodosa


Pinnularia parvulissima

LM scalebar = 10 µm = 40 pixels.


Contributor: Loren Bahls - March 2014
Length Range: 43-70 µm
Width Range: 7.7-10.6 µm
Striae in 10 µm: 10


Valves are linear with triundulate margins. In the largest specimens, the central undulation is wider than the distal undulations. Apices are distinctly capitate. Axial areas are about one-third the valve width and become wider from the apices towards the valve center. The central area is a bilateral fascia. The surface of the valve is mottled along either side of the raphe, continuing into the central area. The raphe is straight. Proximal raphe ends are bent to one side and terminate in small tear-shaped pores. Distal raphe fissures are shaped like question marks. Striae are weakly radiate at the valve center, becoming strongly convergent at the apices.

Original Description

Author: Krammer 2000
Length Range: 47-61 µm
Width Range: 9-10 µm
Striae in 10 µm: 8-10

Original Description

Original Images

Cite This Page:
Bahls, L. (2014). Pinnularia nodosa. In Diatoms of the United States. Retrieved April 26, 2018, from

Species: Pinnularia nodosa

Contributor: Loren Bahls

Reviewer: Sam Rushforth


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

Links & ID's

Index Nominum Algarum (INA)

Original INA

California Academy of Sciences (CAS)

Pinnularia nodosa var. percapitata CAS

North American Diatom Ecological Database (NADED)


Autecology Discussion

The specimens of P. nodosa var. percapitata observed are from streams, ponds and small lakes in the northern Rocky Mountains of Montana. At these locations pH ranged from 6.10 to 7.78 and specific conductance ranged from 22 to 169 µS/cm. Water quality preferences of this variety appear to be similar to those of the nominate variety: low to moderate electrolyte content and low pH, most commonly found in peaty bogs and in springs (Krammer 2000).


Indian Meadows Research Natural Area, Helena National Forest, Lewis & Clark County, Montana: home of Pinnularia nodosa var. percapitata.

Credit/Source: Loren Bahls