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Neidium undulatum

L.L.Bahls 2013      Category: Symmetrical biraphid
BASIONYM: Neidium kozlowi var. undulata Stoermer 1963

REPORTED AS: Neidium kozlowii (Krammer and Lange-Bertalot 1986, p. 276, fig. 102: 12-13) 

Neidium sacoense


Nitzschia acicularis

LM scalebar = 10 µm = 40 pixels.


Contributor: Loren Bahls - April 2013
Length Range: 82-110 µm
Width Range: 23-26 µm
Striae in 10 µm: 10-12


Valves are elliptic-lanceolate with gradually protracted, relatively narrow subrostrate apices. A longitudinal line is evident along each margin. The axial area is rather broad and includes a row of irregularly spaced areolae along one side of both raphe branches. The central area is rectangular and positioned diagonally to the valve midline. Short striae, composed of areolae of irregular size and spacing, occur along both margins of the central area. The raphe is lateral, becoming filiform at the proximal ends. The proximal raphe ends are deflected sharply in opposite directions. The distal raphe fissures are bifurcate. Striae near the valve center are arranged diagonally with respect to the valve midline and become convergent towards the apices.

Original Description

Basionym: Neidium kozlowi var. undulata
Author: Stoermer 1963
Length Range: 98 µm
Width Range: 24 µm
Striae in 10 µm: 10-12

Original Description

Valves long elliptic-lanceolate with triundulate margins and rather long broadly rounded sub-rostrate ends. Striae diagonal to midline of valve, having tendency to radiate in central portion of valve and to become parallel or slightly convergent at ends. Striae distinctly punctate. Axial area fairly broad, slightly diagonal, to perapical axis. Central area rectangular, distinctly diagonal, at margins of valve not sharply defined due to irregularity of striae. Both axial and central areas often have scattered punctae of somewhat abnormal appearance. Raphe generally linear, often appearing undulate due to contour of valve. Proximal raphe hooks short, attenuate, distal raphe ends narrowly bifurcate.

Original Images

Cite This Page:
Bahls, L. (2013). Neidium undulatum. In Diatoms of the United States. Retrieved May 23, 2018, from

Species: Neidium undulatum

Contributor: Loren Bahls

Reviewer: Sarah Spaulding


Bahls, L. (2013). New diatoms (Bacillariophyta) from western North America. Phytotaxa 82(1): 7-28.

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.

Mereschkowsky, C. 1906. Diatomées du Tibet. Imperial Russkoe geograficheskoe obshchestvo. St. Petersburg 40 pp. (1906). Diatomées du Tibet. Imperial Russkoe geograficheskoe obshchestvo, St. Petersburg. 40 pp.

Metzeltin, D., Lange-Bertalot, H. and Soninkhishig, N. (2009). Diatoms in Mongolia. Iconographia Diatomologica (H. Lange-Bertalot, ed.), Vol. 20, A. R. G. Gantner Verlag K. G., Ruggell, 691 pp.

Stoermer, E.F. (1963). New taxa and new United States records of the diatom genus Neidium from West Lake Okoboji, Iowa. Notulae Naturae 358: 1-9.

Links & ID's

Index Nominum Algarum (INA)

Original INA

California Academy of Sciences (CAS)

Neidium undulatum CAS

North American Diatom Ecological Database (NADED)


Autecology Discussion

In addition to the type locality, Neidium undulatum was collected from Grassy Lake in the Axolotl Lakes near Ennis, Montana, elevation 2290 m. On the date the Grassy Lake sample was collected (29 September 2011), pH measured 9.73 and specific conductance measured 177 µS/cm.


Grassy Lake in the Axolotl Lakes near Ennis, Madison County, Montana: home of Neidium undulatum.

Credit/Source: Loren Bahls