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Brachysira serians

(Bréb.) Round and D.G.Mann 1981      Category: Symmetrical biraphid
BASIONYM: Frustulia serians Bréb. 1838
SYNONYM(S): Anomoeoneis serians (Bréb.) Cleve | Navicula serians Bréb. ex Kütz. 

Brachysira ocalanensis


Brachysira styriaca

LM scalebar = 10 µm = 40 pixels.


Contributor: Paul Hamilton - December 2010
Length Range: 50-123 µm
Width Range: 14-19 µm
Striae in 10 µm: 18-23


Valves are lanceolate with narrowly rounded apices. The striae are slightly radiate to parallel throughout the valve. At the apices, the striae are composed of a single areola. The axial area is linear and distinct; the central area is asymmetrically rounded. The raphe is positioned between two external, longitudinal ribs. The raphe is straight with straight proximal fissures and T-shaped distal fissures. Areolae are elongated rectangular slits with rounded ends, oriented to the transapical axis. Spaces between the areolae give the appearance of longitudinal undulations. Thick, external ribs are present at the valve margins. The mantle possesses a single row of elongated areolae. One or two Voigt faults are present on the secondary side of the axial area.

In SEM, the internal distal raphe fissures terminate at small helictoglossae. The areolae are covered internally with flat hymenes. Externally, a series of siliceous ridges may extend longitudinally on the valve face.

The first description of B. serians appeared in Kutzing (1844), with a valve length of 94 µm. Kutzing’s illustration (Taf. 30, fig. 23) presents the species in valve and girdle views.

Original Description

Basionym: Frustulia serians
Author: Bréb. 1838
Length Range: µm
Striae in 10 µm:

Original Description

Original Images

Cite This Page:
Hamilton, P. (2010). Brachysira serians. In Diatoms of the United States. Retrieved May 20, 2018, from

Species: Brachysira serians

Contributor: Paul Hamilton

Reviewer: Sarah Spaulding


Brébisson, A. de. (1838). Considérations sur les Diatomées et essai d’une classification des genres et des espèces appartenant à cette famille. Brée l'Ainé Imprimeur-Libraire, Falaise. 22 pp.

Camburn, K.E. and Charles, D.F. (2000). Diatoms of Low-Alkalinity Lakes in the Northeastern United States. Academy of Natural Sciences of Philadelphia, Special Publication 18, 152 pp.

Gaiser, E.E. and Johansen, J. (2000). Freshwater diatoms from Carolina bays and other isolated wetlands on the Atlantic Coastal Plain of South Carolina, USA, with descriptions of seven taxa new to science. Diatom Research 15(1): 75-130. 10.1080/0269249X.2000.9705487

Kützing, F.T. (1844). Die kieselschaligen Bacillarien oder Diatomeen. Nordhausen. 152 pp., 30 pls.

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

Metzeltin, D. and Lange-Bertalot, H. (2007). Tropical Diatoms of South America II. Iconographia Diatomologica 18, 1-877.

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.

Round, F.E. and Mann, D.G. (1981). The diatom genus Brachysira. I. Typification and separation from Anomoeneis. Archiv Protistenkunde 124: 221-231.

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.

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.

Links & ID's

Index Nominum Algarum (INA)

Transfer INA

California Academy of Sciences (CAS)

Brachysira serians CAS

North American Diatom Ecological Database (NADED)

NADED ID: 18003

Autecology Discussion

Brachysira serians was reported in acidic and humic stained waterbodies of the eastern United States, but in abundances less than 10% (Siver et al. 2005; Siver and Hamilton, 2011). A preference for acidic habitats was also noted by other authors (Patrick and Reimer, 1966; Lange-Bertalot and Moser, 1994; Camburn and Charles, 2000; Gaiser and Johansen, 2000). Optima for pH and TP from these works range between 4.0-5.2 and 4.3-15.6 µg/L, respectively.