Gomphonema semiapertum

Grunow in Van Heurck 1880      Category: Asymmetrical biraphid

Gomphonema sarcophagus


Gomphonema sierrianum

LM scalebar = 10 µm = 40 pixels.


Contributor: Loren Bahls - February 2017
Length Range: 74-113 µm
Width Range: 10.3-14.1 µm
Striae in 10 µm: 9-12


Valves are lanceolate-clavate, with a rounded headpole and a narrower footpole. Striae are parallel to slightly radiate at the center of the valve, becoming more radiate near the apices. Striae are composed of a single row of distinct areolae that number 25-30 in 10 µm. The central axial area is wide and each branch is lanceolate. The central area is large, asymmetric and rectangular to elliptic. One side of the central area extends all the way to the valve margin; the other side is delimited by 3-5 shortened striae. One isolated stigma is located close to the proximal raphe ends on one side of the central nodule. The raphe is strongly lateral. Proximal raphe ends are small and inconspicuous. On deep focus, the internal proximal raphe ends are steeply deflected, into the shape of a barb, on the same side as the stigma. Terminal raphe ends are comma-shaped. The terminal raphe end at the footpole bisects a distinct apical pore field.

This is a large and distinctive but quite uncommon taxon, with extant populations apparently restricted to the Cascade Mountains of California and Oregon.

Original Description

Author: Grunow in Van Heurck 1880
Length Range: µm
Striae in 10 µm:

Original Description

Gomphonema semiapertum was originally published without a description.

Original Images

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

Species: Gomphonema semiapertum

Contributor: Loren Bahls

Reviewer: Sarah Spaulding


Hanna, G.D. (1932). Pliocene diatoms of Wallace County, Kansas. Univ. Kansas Sci. Bull., 20(21): 369-395.

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.

Schmidt, A. (-). (1874-1959). Atlas der Diatomaceen-Kunde, von Adolf Schmidt, continued by Martin Schmidt, Friedrich Fricke, Heinrich Heiden, Otto Muller, Friedrich Hustedt. Reprint 1984, Koeltz Scientific Books, Konigstein, 480 plates.

Van Heurck, H. (1880). Synopsis des Diatomées de Belgique. Atlas. Ducaju & Cie., Anvers.

Links & ID's

Index Nominum Algarum (INA)

Original INA

California Academy of Sciences (CAS)

North American Diatom Ecological Database (NADED)


Autecology Discussion

The specimens pictured here were collected from three streams in the Cascade Mountains of western Oregon. One of these streams, Bessie Creek, is shown below. At the time of collection, these streams had a mean conductivity of 38 µS/cm-1, pH of 7.1, mean temperature of 4.9 degrees C and mean dissolved oxygen of 12.86 mg/L. Given these water quality characteristics, the conclusion of Patrick & Reimer (1975) that G. semiapertum prefers “water with fairly high conductivity” is questionable.

The original collection examined by Grunow was from Shasta County in northern California. Patrick & Reimer (1975) also report Gomphonema semiapertum from Oregon and unverified records from Michigan and Illinois. In addition, it was reported as a Pliocene fossil from a freshwater lake deposit in Kansas (Hanna 1932).


Distribution of Gomphonema semiapertum based on samples in the Montana Diatom Collection.

Credit/Source: Google Earth

Bessie Creek, Klamath County, Oregon: home of Gomphonema semiapertum.

Credit/Source: U. S. Forest Service

Bessie Creek, Klamath County, Oregon: home of Gomphonema semiapertum.

Credit/Source: U. S. Forest Service

Bessie Creek, Klamath County, Oregon: home of Gomphonema semiapertum.

Credit/Source: U. S. Forest Service