Brachysira hannae

(Reimer) Lange-Bert. and Gerd Moser 1994      Category: Symmetrical biraphid
BASIONYM: Anomoeoneis follis var. hannae Reimer 1966

Brachysira brebissonii


Brachysira microcephala

LM scalebar = 10 µm = 40 pixels.


Contributor: Paul Hamilton - December 2010
Length Range: 30-60 µm
Width Range: 14-19 µm
Striae in 10 µm: 20-22


Valves are rhombic with straight margins and rounded apices. Striae are radiate throughout valve. The central area is asymmetrically rounded and axial area is narrow and straight. Striae at the center valve margin are short, and not interrupted. The raphe is positioned within two longitudinal ribs on the external valve face. The ribs terminate at the edge of the central area and the apices. Raphe is straight and filiform. The proximal fissures are undifferentiated and the distal fissures are T-shaped. Areolae are variable in shape, mostly elongate with respect to the transapical axis. The orientation and irregular size of the areolae creates a series of wavy hyaline areas. Small papillae (visible in SEM) may be positioned on rows between the striae. A thickened rib is present along the valve margin and apex, separating the valve face from the mantle. Striae on the mantle are uniseriate and aligned with striae on the valve face.

In SEM, the internal proximal raphe fissures terminate at a small helictoglossa. Areolae are covered internally with flat, well-defined hymenes. Externally, a well-defined, thick rib defines the valve face / mantle interface. The mantle contains a single row of elongated pores, each of which is covered internally by a hymen.

Original Description

Basionym: Anomoeoneis follis var. hannae
Author: Reimer 1966
Length Range: 25-73 µm
Width Range: 13-21 µm
Striae in 10 µm: 21-22

Original Description

Valves rhombic; ends obtusely rounded. Axial area narrow. Central area somewhat angular. Raphe straight filiform. Striae radiate throughout, occasionally the last three or four striae at the ends may be parallel. A few short striae may be interposed between the longer striae on either side of the central area. Striae punctate. Length 25-73 µm; width 13-21 µm; striae 21-22/10 µm

Original Images

Original text and images reproduced with permission by Academy of Natural Sciences of Philadelphia.

Cite This Page:
Hamilton, P. (2010). Brachysira hannae. In Diatoms of the United States. Retrieved April 26, 2018, from

Species: Brachysira hannae

Contributor: Paul Hamilton

Reviewer: Sarah Spaulding


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

Patrick, R.M. and Reimer, C.W. (1966). The Diatoms of the United States exclusive of Alaska and Hawaii, V. 1. Monographs of the Academy of Natural Sciences of Philadelphia 13.

Reimer, C.W. (1961). New and variable taxa of the diatom genera Anomoneis Pfitz. and Stauroneis Her. (Bacillariophyta) from the United States. Proc. Acad. Nat. Sci. Philadelphia 113: 187-214.

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. and Hamilton, P.B. (2011). Diatoms of North America: The Freshwater Flora of Waterbodies on the Atlantic Coastal Plain. Iconographia Diatomologica 22.

Links & ID's

Index Nominum Algarum (INA)

California Academy of Sciences (CAS)

Brachysira hannae CAS

North American Diatom Ecological Database (NADED)


Autecology Discussion

Little is known about the ecology of B. hannae, since it is rarely reported. The lmited records are from acidic, humic strained waters.