Stauroneis gracilis

Ehrenb. 1843      Category: Symmetrical biraphid

Stauroneis fluminopsis


Stauroneis heinii

LM scalebar = 10 µm = 40 pixels.


Contributor: Loren Bahls - December 2011
Length Range: 68-127 µm
Width Range: 13-22 µm
Striae in 10 µm: 15-18


Valves are elliptic-lanceolate with subrostrate, broadly rounded apices. The axial area is linear to narrowly lanceolate and two to three times wider than the raphe. The stauros is rectangular, often widening slightly towards the valve margins. Short striae are absent from the central area. The raphe is lateral with curved and inflated proximal ends. Terminal raphe fissures are shaped like question marks and hooked toward the secondary side. Striae are radiate throughout. Areolae number 18-22 in 10 µm.

Original Description

Author: Ehrenb. 1843
Length Range: µm
Striae in 10 µm:

Original Description

Original Images

Cite This Page:
Bahls, L. (2011). Stauroneis gracilis. In Diatoms of the United States. Retrieved April 21, 2018, from

Species: Stauroneis gracilis

Contributor: Loren Bahls

Reviewer: Mark Edlund


Bahls, L. (2010). Stauroneis in the Northern Rockies: 50 species of Stauroneis sensu stricto from western Montana, northern Idaho, northeastern Washington and southwestern Alberta, including 16 species described as new. Northwest Diatoms, Volume 4. The Montana Diatom Collection, Helena, 172 pp.

Ehrenberg, C.G. (1843). Verbreitung und Einfluß des mikroskopischen Lebens in Süd- und Nord-Amerika. Abhandlungen der Königlichen Akademie der Wissenschaften zu Berlin, 1841: 291-445, 4 Tafel.

Reichardt, E. (1995). Die Diatomeen (Bacillariophyceae) in Ehrenbergs Material von Cayenne, Guyana Gallica (1843). Volume 1, Iconographia Diatomologica (H. Lange-Bertalot, ed.). Koeltz Scientific Books, Konigstein.

Van de Vijver, B., Beyens, L. and Lange-Bertalot, H. (2004). The genus Stauroneis in Arctic and Antarctic Regions. Bibliotheca Diatomologica 50, 312 pp.

Links & ID's

Index Nominum Algarum (INA)

Original INA

California Academy of Sciences (CAS)

Stauroneis gracilis CAS

North American Diatom Ecological Database (NADED)


Autecology Discussion

Stauroneis gracilis is widely distributed in lakes, ponds, and wetlands in the Northern Rockies. The pH of these waters ranges from 5.5 to 7.4 (mean pH = 6.7) and specific conductance ranges from 7 to 192 µS/cm (mean SC = 36 µS/cm). Van de Vijver et al. (2004) report this species as widely distributed in both the Arctic and Antarctic, where it is present in a large variety of habitats ranging from small, very shallow pools to large, deep lakes. In these waters the pH ranges from 6.0 to 8.3 and specific conductance ranges from 50 to 350 µS/cm.


Red Eagle Pond, Glacier National Park, Montana: home of Stauroneis gracilis.

Credit/Source: E. William Schweiger, National Park Service