Planothidium rostratum

(Østrup) Lange-Bert. 1999      Category: Monoraphid
BASIONYM: Achnanthes rostrata Østrup 1902
SYNONYM(S): Achnanthes lanceolata subsp. rostrata  (Østrup) Lange-Bert. 

Planothidium lanceolatum


Platessa bahlsii

LM scalebar = 10 µm = 80 pixels.


Contributor: Marina Potapova - December 2010
Length Range: 11-18 µm
Width Range: 5.0-6.0 µm
Striae in 10 µm: 11-13


Valves are linear-elliptical with rostrate, subrostrate or narrowly subcapitate apices. The raphe valve has a linear axial area and central area that varies in shape - from transversely rectangular to elliptical. The rapheless valve has a linear-lanceolate axial area, which in some populations, widens considerably in the valve center. The rapheless valve has a linear-lanceolate axial area and an asymmetrical central area containing a hood on the internal valve surface. The raphe is straight with expanded external proximal endings. Terminal raphe fissures are curved to the secondary side of the valve. The striae are multiseriate and radiate throughout both valves.

Original Description

Basionym: Achnanthes rostrata
Author: Østrup 1902
Length Range: 12 µm
Width Range: 6 µm
Striae in 10 µm: 10

Original Description

L. 0,012 mm., B. 0,006 mm. Striæ 10 in 0,01 mm. The outline of both valve identical: elliptical with rostrate apices. Epitheca with an unilateral horseshoe-shaped mark, Hypotheca: central pores approximate, unilateral central area

Original Images

Cite This Page:
Potapova, M. (2010). Planothidium rostratum. In Diatoms of the United States. Retrieved April 23, 2018, from

Species: Planothidium rostratum

Contributor: Marina Potapova

Reviewer: Sarah Spaulding


Lange-Bertalot, H. (1999). Neue Kombinationen von taxa aus Achnanthes Bory (sensu lato). Iconographia Diatomologica 6: 276-289.

Moss, M.O. and Carter, J.R. (1982). The resurrection of Achnanthes rostrata Ostrup. Bacillaria 5: 147-164.

Østrup, E. (1902). Freshwater Diatoms [in Flora of Koh Chang. Part VII. Contributions to the knowledge of the gulf of Siam.John Schmidt (ed.). Preliminary Rept. Bot., Results Dan. Exped. to Siam (1899-1900)]. Botanisk Tidsskrift 25(1): 28-41.

Links & ID's

Index Nominum Algarum (INA)

California Academy of Sciences (CAS)

Planothidium rostratum CAS

North American Diatom Ecological Database (NADED)

NADED ID: 155018

Autecology Discussion

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

Planothidium rostratum

EMAP Response Plots

Planothidium rostratum

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.