Gyrosigma attenuatum

(Kütz.) Rabenh. 1853      Category: Symmetrical biraphid
BASIONYM: Frustulia attenuata Kütz. 1833
SYNONYM(S): Navicula attenuata (Kütz.) Kütz. 1844 | Gyrosigma attenuata (Kützing) Cleve 1894 

Gyrosigma acuminatum


Halamphora coffeaeformis

LM scalebar = 10 µm = 20 pixels.


Contributor: Joanna Gauthier - June 2015
Length Range: 130-255 µm
Width Range: 20-28 µm
Striae in 10 µm: 12-14 transverse; 10-12 longitudinal


Valves are narrowly lanceolate and moderately sigmoid. The central area is small, longitudinally elliptical and, in some cases, irregular. The raphe is straight for at least 2/3 of its length and positioned in the center of the valve. Near the apices, the raphe becomes sigmoid. The proximal raphe ends are deflected to opposite sides of the valve near to where the axial area widens to form the central area. The axial area is narrow, widening at each end of the valve into a triangular shape. The distal raphe ends are deflected to opposite directions. The longitudinal striae are parallel to the axial area, including at the center of the valve where the central area widens. The longitudinal striae are more coarse than the transverse striae.

Original Description

Basionym: Frustulia attenuata
Author: Kütz. 1833
Length Range: µm
Striae in 10 µm:

Original Description

Original Images

Cite This Page:
Gauthier, J. (2015). Gyrosigma attenuatum. In Diatoms of the United States. Retrieved April 21, 2018, from

Species: Gyrosigma attenuatum

Contributor: Joanna Gauthier

Reviewer: Kalina Manoylov


Cleve, P.T. (1894). Synopsis of the Naviculoid Diatoms, Part I. Kongliga Svenska-Vetenskaps Akademiens Handlingar 26(2):1-194, 5 pls.

Hofmann, G., Werum, M. and Lange-Bertalot, H. (2011). Diatomeen im Süßwasser-Benthos von Mitteleuropa. Koeltz Scientific Books, Königstein, 908 pp.

Kützing, F.T. (1833). Synopsis Diatomacearum oder Versuch einer systematischen Zusammenstellung der Diatomeen. Linnaea 8(5): 529-620, pls. XIII-XIX.

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.

Rabenhorst, L. (1853). Die Süßwasser-Diatomaceen (Bacillarien) für Freunde der Mikroskopie. Leipzig, 72 pp.

Links & ID's

Index Nominum Algarum (INA)

Original INA
Transfer INA
Transfer INA

California Academy of Sciences (CAS)

Gyrosigma attenuatum CAS

North American Diatom Ecological Database (NADED)

NADED ID: 38005

Autecology Discussion

Gyrosigma attenuatum is widely distributed in the U.S. (Patrick and Reimer 1966), but is rarely found in high densities in water bodies (Lange-Bertalot 2011). This species prefers alkaline water environments and is relatively sensitive to organic load from outflows in its environment (Lange-Bertalot 2011).


Distribution of Gyrosigma attenuatum in the continental U.S. rivers sampled for the National Water Quality Assessment program. Retrieved on June 15, 2015.

Credit/Source: USGS BioData

EMAP Assessment

The Environmental Protection Agency (EPA) western Environmental Monitoring and Assessment Program (EMAP) study was completed during the years 2000-2004 (see citations at bottom of this page). Over 1200 streams and rivers in 12 western states (Arizona, California, Colorado, Idaho, Montana, Nevada, North Dakota, Oregon, South Dakota, Utah, Washington and Wyoming) were selected for sampling based on a stratified randomized design. This type of design insures that ecological resources are sampled in proportion to their actual geographical presence. Stratified randomized design also allows for estimates of stream length with a known confidence in several “condition classes” (good or least-disturbed, intermediately-disturbed, and poor or most-disturbed) for biotic condition, chemistry and habitat.

EMAP Distribution

Gyrosigma attenuatum

EMAP Response Plots

Gyrosigma attenuatum

EMAP citations

Results are published in:

Johnson, T., Hermann, K., Spaulding, S., Beyea, B., Theel, C., Sada, R., Bollman, W., Bowman, J., Larsen, A., Vining, K., Ostermiller, J., Petersen, D. Hargett, E. and Zumberge, J. (2009). An ecological assessment of USEPA Region 8 streams and rivers. U.S. Environmental Protection Agency Region 8 Report, 178 p.

Stoddard, J. L., Peck, D. V., Olsen, A. R., Larsen, D. P., Van Sickle, J., Hawkins, C. P., Hughes, R. M., Whittier, T. R., Lomnicky, G. A., Herlihy, A. T., Kaufman, P. R., Peterson, S. A., Ringold, P. L., Paulsen, S. G., and Blair, R. (2005). Environmental Monitoring and Assessment Program (EMAP) western streams and rivers statistical summary. U.S. Environmental Protection Agency Report 620/R-05/006, 1,762 p.

Stoddard, J. L., Peck, D. V., Paulsen, S. G., Van Sickle, J., Hawkins, C. P., Herlihy, A. T., Hughes, R. M., Kaufman, P. R., Larsen, D. P., Lomnicky, G. A., Olsen, A. R., Peterson, S. A., Ringold, P. L., and Whittier, T. R. (2005). An ecological assessment of western streams and rivers. U.S. Environmental Protection Agency Report 620/R-05/005, 49 p.