Rossithidium petersenii

(Hust.) Aboal in Aboal, Alvarez-Cobelas, Cambra and Ector 2003      Category: Monoraphid
BASIONYM: Achnanthes petersenii Hust. 1937

Rossithidium nodosum


Rossithidium pusillum

LM scalebar = 10 µm = 80 pixels.


Contributor: Marina Potapova - May 2010
Length Range: 13-19 µm
Width Range: 3.5-4.5 µm
Striae in 10 µm: 32-36


Valves are linear or linear-elliptical with rounded ends. The raphe valve has a narrow axial area and a large rectangular or transversely elliptical central area that almost reaches the valve margins. The raphe is straight, filiform, and lacks terminal fissures. Internally, the central raphe endings are curved to opposite sides. The rapheless valve has a narrowly rhomboid axial area and no distinct central area. Striae are uniseriate and slightly radiate. Each stria in the middle part of the valve contains 5-7 areolae. The valve mantle bears one row of areolae.

Original Description

Basionym: Achnanthes petersenii
Author: Hust. 1937
Length Range: 12-17 µm
Width Range: 3.5-4 µm
Striae in 10 µm: 36 in the middle, about 40 at the poles

Original Description

Zellen mit schwach verkieselten Membranen, sehr hyalin. Schalen linear-elliptish, gegen die breit gerundeten Enden etwas verschmälert, 12-17 µ lang, 3,5-4 µ breit. Raphenschale mit gerader, fadenförmiger Raphe, Axialarea sehr eng, Zentralarea eine breite, bisanden Schalenrand reichende Querbinde. Transpikalstreifen im mittleren Teil etwa 36 in 10 µ, gegen die Pole enger werdend, bis etwa 40 in 10 µ, durchweg leicht radia. Raphenlose Schale mit schmal linearer, zuweilen in der Mitte etwas erweiterer Pseudoraphe, Transapikalstreifen etwas gröber, im mittleren Teil etwa 30 in 10 µ, gegen Enden ebenfalls enger werdend, durchweg radial. Fig. 10-14.

Original Images

Cite This Page:
Potapova, M. (2010). Rossithidium petersenii. In Diatoms of the United States. Retrieved April 25, 2018, from

Species: Rossithidium petersenii

Contributor: Marina Potapova

Reviewer: Sam Rushforth


Aboal, M., Alvarez-Cobelas, M., Cambra, J. and Ector, L. (2003). Floristic list of non marine diatoms (Bacillariophyceae) of Iberian Peninsula, Balearic Islands, and Canary Islands. Updated taxonomy and bibliography. In: A. Witkowski (ed.), Diatom Monographs. A.R.G. Gantner Verlag K.G., 4: 639 pp.

Hustedt, F. (1937). Sußwasserdiatomeen von Island, Spitzbergen und den Färöer-Inseln. Botanisches Archiv 38:152-207.

Links & ID's

Index Nominum Algarum (INA)

Original INA
Transfer INA

California Academy of Sciences (CAS)

Rossithidium petersenii CAS

NCBI Genbank Taxonomy

Rossithidium petersenii NCBI

North American Diatom Ecological Database (NADED)

NADED ID: 18900

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

Rossithidium petersenii

EMAP Response Plots

Rossithidium petersenii

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.