Gomphonema americobtusatum

E.Reichardt and Lange-Bert. 1999      Category: Asymmetrical biraphid

Gomphonema amerhombicum


Gomphonema apicatum

LM scalebar = 10 µm = 80 pixels.


Contributor: Loren Bahls - May 2017
Length Range: 16-55 µm
Width Range: 6.2-10.1 µm
Striae in 10 µm: 8-12


Valves are lanceolate and slightly heteropolar. Valve apices are obtuse and weakly protracted in some specimens, not protracted in others. The axial area is narrow and linear in smaller specimens, moderately wide and lanceolate in larger specimens. The central area is slightly asymmetric and transversely rectangular. It is bordered by one or two shortened striae on the primary side adjacent to the stigma, and one or two shorter striae on the secondary side of the valve. The raphe is lateral and somewhat sinuous. External proximal raphe ends are weakly expanded and slightly deflected toward the primary side. Terminal raphe ends are are sinuous and deflected toward the secondary side of the valve. Striae are parallel or slightly radiate at the valve center, and become more radiate toward the apices. Areolae in the striae number 28-34 in 10 µm. An initial valve was observed at 55 µm in length.

The relation between this taxon and G. angustatum var. obtusatum (Kützing) Grunow in Van Heurck, as reported from the eastern and central U.S. (Patrick & Reimer 1975), is in need of clarification.

Original Description

Author: E.Reichardt and Lange-Bert. 1999
Length Range: 25-60 µm
Width Range: 8.6-10.7 µm
Striae in 10 µm: 8-10

Original Description

Original Images

Cite This Page:
Bahls, L. (2017). Gomphonema americobtusatum. In Diatoms of the United States. Retrieved April 21, 2018, from http://westerndiatoms.colorado.edu/taxa/species/gomphonema_americobtusatum

Species: Gomphonema americobtusatum

Contributor: Loren Bahls

Reviewer: Ingrid Jüttner


Patrick, R.M. and Reimer, C.W. (1975). The Diatoms of the United States, exclusive of Alaska and Hawaii, V. 2. Monographs of the Academy of Natural Sciences of Philadelphia 13.

Reichardt, E. (1999). Zur Revision der Gattung Gomphonema: Die Arten um G. affine/insigne, G. angustatum/micropus, G. acuminatum sowie gomphonemoide Diatomeen aus dem Oberoligozän in Böhmen. Annotated Diatom Micrographs. Edited by Horst Lange-Bertalot. Iconographia Diatomologica, Volume 8, A.R.G. Gantner.

Links & ID's

Index Nominum Algarum (INA)

Original INA

California Academy of Sciences (CAS)

North American Diatom Ecological Database (NADED)

NADED ID: 37300

Autecology Discussion

Gomphonema americobtusatum was described from Canada. In the Northwest U.S. it is widely distributed in mountain waters, primarily in the Rockies and Cascades, but also on the east side of the Sierra Nevada Range (see map below). Abundance-weighted values for selected water quality variables (table below) suggest that it prefers cool, well-oxygenated, low nutrient and somewhat alkaline water of low conductivity.


Atlantic Pond, Glacier National Park, Montana: home of Gomphonema americobtusatum.

Credit/Source: Loren Bahls

Distribution of Gomphonema americobtusatum in the Northwest United States.

Credit/Source: Montana Diatom Database

Abundance-weighted values of water quality variables for Gomphonema americobtusatum in the Northwest U.S.

Credit/Source: Montana Diatom Database