Brachysira ocalanensis

Shayler and Siver 2004      Category: Symmetrical biraphid

Brachysira neoacuta


Brachysira serians

LM scalebar = 10 µm = 80 pixels.


Contributor: Loren Bahls - March 2014
Length Range: 19-39 µm
Width Range: 4.0-5.7 µm
Striae in 10 µm: 32-34, more closely spaced towards the apices


Valves are lanceolate to linear-lanceolate and sometimes heteropolar. Apices are narrowly rounded or sub-rostrate to weakly subcapitate. The axial area is narrow. The central area is a narrow ellipse oriented lengthwise along the apical axis. The raphe is straight. Proximal raphe ends are weakly expanded and relatively distant from one another. Striae are radiate. Areolae are transapically elliptic to bacilliform. Areolae are irregularly spaced, creating a pattern of undulating longitudinal lines.

Original Description

Author: Shayler and Siver 2004
Length Range: 21.5-35.5 µm
Width Range: 4-6 µm
Striae in 10 µm: 33-43

Original Description

Original Images

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

Species: Brachysira ocalanensis

Contributor: Loren Bahls

Reviewer: Marina Potapova


Lange-Bertalot, H. and Moser, G. (1994). Brachysira Monographie der Gattung. Bibliotheca Diatomologica 29: 1-212.

Shayler, H.A. and Siver, P.A. (2004). Biodiversity of the genus Brachysira in the Ocala National Forest, Florida, U.S.A. Proceedings of the Seventeenth International Diatom. Symposium Ottawa, Canada, 25th – 31st August 2002 (M. Poulin, ed.), Biopress limited, Bristol. p. 309-333.

Siver, P.A., Hamilton, P.B., Stachura-Suchoples, K. and Kociolek, J.P. (2005). Diatoms of North America. The Freshwater Flora of Cape Cod. Iconographia Diatomologica 14: 1-463.

Wolfe, A.P. and Kling, H.J. (2001). A consideration of some North American soft-water Brachysira taxa and description of B. arctoborealis sp. nov. Lange-Bertalot-Festschrift Studies on Diatoms, Dedicated to Dr. Dr. h.c. Horst Lange-Bertalot on the occasion of his 65th birthday.

Links & ID's

Index Nominum Algarum (INA)

Original INA

California Academy of Sciences (CAS)

North American Diatom Ecological Database (NADED)

NADED ID: 18046

Autecology Discussion

The images of B. ocalanensis on this website are from Johns Lake in Glacier National Park, Montana (photo below). On the collection date, the pH of Johns Lake was 7.24 and specific conductance measured 30 µS/cm. It has also been recorded from other lakes in Glacier National Park. This species was described from Wildcat Lake on the Ocala National Forest in Florida, which had a pH of 4.83 and a specific conductance of 52.4 µS/cm (Shayler & Siver 2004). It may seem odd that a species described from Florida would appear in the mountains of northwest Montana, but consider that B. arctoborealis, a species described from the Canadian Arctic, has also been reported from the Cascade Mountains of Washington, from Florida, and even from Borneo!


Johns Lake, Glacier National Park, Montana: home of Brachysira ocalanensis.