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Geissleria decussis

(Østrup) Lange-Bert. and Metzeltin 1996      Category: Symmetrical biraphid
BASIONYM: Navicula decussis Østrup 1910

Geissleria acceptata


Geissleria ignota

LM scalebar = 10 µm = 80 pixels.


Contributor: Marina Potapova - March 2009
Length Range: 16-30 µm
Width Range: 6–9 µm
Striae in 10 µm: 14-18


Valves are elliptical-lanceolate with rostrate to capitate apices, 6-9 µm wide and 16-30 µm long. The raphe is straight and filiform. Externally, the proximal raphe ends are surrounded by two small grooves. The axial area is narrow and linear. The central area is rectangular to irregular in shape, with an isolated stigma. Striae are uniseriate and radiate, becoming parallel or slightly convergent at the ends. The striae are also usually deflected, or bent, and number 14-18 in 10 µm. Short and long striae alternate in the central valve. Areolae are apically elongated and number approximately 60-70 in 10 µm. Subpolar areolae (annulae) are larger than the other areolae, forming two rows on either side of the raphe at the poles. Internally, the annulae are surrounded by spherical nodules, typical of the genus Geissleria.

Original Description

Basionym: Navicula decussis
Author: Østrup 1910
Length Range: 16-22 µm
Width Range: 6–7 µm
Striae in 10 µm: 16-20

Original Description

Long. 16-22 µ, Lat.6-7 µ. Str. 16-20 in 10 µ, transverse lineatis. Valva elliptica, apicibus capitatis. Raphe directa, area hyalina angusta, media in parte valvae in aream transersam dilatata, cincta. Striis radiantibus, in apicibus convergentibus, mediis tribus longiudine diversa itaqve inter se remotis, ut amplificatione mediocre figura decussis existat. Nodulis terminalibus summis in apicibus situatis.

Original Images

Cite This Page:
Potapova, M. (2009). Geissleria decussis. In Diatoms of the United States. Retrieved May 22, 2018, from

Species: Geissleria decussis

Contributor: Marina Potapova

Reviewer: Sarah Spaulding


Lange-Bertalot, H. and Metzeltin, D. (1996). Indicators of oligotrophy - 800 taxa representative of three ecologically distinct lake types, Carbonate buffered - Oligodystrophic - Weakly buffered soft water. Lange-Bertalot, H. (ed.), Iconographia Diatomologica. Annotated Diatom Micrographs. Vol. 2. Ecology, Diversity, Taxonomy. Koeltz Scientific Books. Königstein, Germany, 2:390 pp.

Østrup, E. (1910). Danske Diatoméer. C.A. Reitzels Boghandel, Kjøbenhavn. 323 pp., 5 pls.

Links & ID's

Index Nominum Algarum (INA)

Original INA

California Academy of Sciences (CAS)

Geissleria decussis CAS

NCBI Genbank Taxonomy

Geissleria decussis NCBI

North American Diatom Ecological Database (NADED)

NADED ID: 210003

Autecology Discussion

Fresh waters of moderate to high ionic strength

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

Geissleria decussis

EMAP Response Plots

Geissleria decussis

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.