Rossithidium nodosum

(A.Cleve) Aboal 2003      Category: Monoraphid
BASIONYM: Achnanthes nodosa A.Cleve 1900

Rossithidium anastasiae


Rossithidium petersenii

LM scalebar = 10 µm = 80 pixels.


Contributor: Marina Potapova - May 2009
Length Range: 9-12 µm
Width Range: 2.9-3.3 µm
Striae in 10 µm: 16-20


Valves are linear to linear-elliptical with rounded ends, which are slightly drawn-out. Raphe valve has narrow axial area, which widens into a small central area. Distal raphe ends are externally curved towards the same side of the valve and slightly expanded at their ends. Central raphe ends are slightly expanded externally, curved to opposite sides internally. Rapheless valve has narrowly linear axial area, which sometimes widens unilaterally into a small central area. Striae on both valves are biseriate. Areolae are elliptical or angular, transapically elongated. Internally areoale are covered by hymens. Striae are slightly radiate throughout both valves. Striae number 16-20 in 10 µm. Valve mantle bears one row of elongated areolae: there is one areola opposite to a stria, and one between striae.

Original Description

Basionym: Achnanthes nodosa
Author: A.Cleve 1900
Length Range: 15-26 µm
Width Range: 5–7 µm
Striae in 10 µm: 14-17

Original Description

Schalen linear mit etwas erweiterter Mitte und schwasch kopfformigen stumpfen Enden. Lange 15-26 µm, Breite 5-6 µm, Querstreifen 14-17 in 0.01 µm, stark und deutlich punktiert, an der Unterschale etwas radial, an der Oberschale parallel und bisweilen in der Mitte fehlend.

Original Images

Cite This Page:
Potapova, M. (2009). Rossithidium nodosum. In Diatoms of the United States. Retrieved April 20, 2018, from

Species: Rossithidium nodosum

Contributor: Marina Potapova

Reviewer: Sarah Spaulding


Aboal, M., Puig, M.A. and Soler, G. (1996). Diatom assemblages in some Mediterranean temporary streams in southeastern Spain. Archiv fur Hydrobiologie 136: 509-527.

Cleve, A. (1900). Beitrage zur flora der Baren-Insel. Diatomeen. Konliga Svenska Vetenskaps-Akademiens Handlingar, Bihang, 26, Afd. III, No.10, pp. 1-25.

Links & ID's

Index Nominum Algarum (INA)

Transfer INA
Original INA

California Academy of Sciences (CAS)

Rossithidium nodosum CAS

North American Diatom Ecological Database (NADED)

NADED ID: 189006

Autecology Discussion

reported from oligotrophic cold waters

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 nodosum

EMAP Response Plots

Rossithidium nodosum

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.


- Achnanthes nodosa transferred to Rossithidium nodosum

Achnanthes nodosa was transferred to Rossithidium nodosum by Aboal in 2003. The transfer is now reflected in the website. Sarah Spaulding