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Planothidium frequentissimum

(Lange-Bert. in Krammer and Lange-Bert.) Lange-Bert. 1999      Category: Monoraphid
BASIONYM: Achnanthes lanceolata subsp. frequentissima Lange-Bert. 1993

Planothidium dubium


Planothidium haynaldii

LM scalebar = 10 µm = 80 pixels.


Contributor: Marina Potapova - December 2010
Length Range: 5-17 µm
Width Range: 3-6 µm
Striae in 10 µm: 13-18


Valves are lanceolate to elliptical with rounded or slightly drawn-out apices. The raphe valve has a linear axial area and central area that is variable in shape - from transversely rectangular to elliptical. The rapheless valve has a linear-lanceolate axial area that slightly widens in the center. The asymmetrical central area on rapheless valve contains 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 lanceolata subsp. frequentissima
Author: Lange-Bert. 1993
Length Range: 4-36 µm
Width Range: 2.5-6.5 µm
Striae in 10 µm:

Original Description

Valvae ellipticae finibus plerumque non protractis obtuse ad late rotundatis nonnumquam paulo protractis numquam abrupte rostrato-protractis. Longitudo 4-36 μm, latitude 2,5-6,5 μm. Raphovalva ab Achnanthes lanceolata ssp. lanceolata non differt. Areovalva nunc autem differt constructione particulare »cavum tectum« dictum nec »sinus« i.e. caverna aperta. Itaque ssp. frequentissima singulari complexione signorum typicorum est distinguenda subspeciebus lanceolata, rostrata, dubia, biporoma, robusta, apiculata, lanceolatoides

Original Images

Cite This Page:
Potapova, M. (2010). Planothidium frequentissimum. In Diatoms of the United States. Retrieved May 20, 2018, from

Species: Planothidium frequentissimum

Contributor: Marina Potapova

Reviewer: Sarah Spaulding


Lange-Bertalot, H. (1993). 85 Neue taxa und uber 100 weitere neu definierte Taxa erganzend zur Subwasserflora von Mittleuropa. Bibliotheca Diatomologica 27, 454 p. Cramer, Berlin, Stuttgart.

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

Links & ID's

Index Nominum Algarum (INA)

Transfer INA

California Academy of Sciences (CAS)

Planothidium frequentissimum CAS

NCBI Genbank Taxonomy

Planothidium frequentissimum NCBI

North American Diatom Ecological Database (NADED)

NADED ID: 155017

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 frequentissimum

EMAP Response Plots

Planothidium frequentissimum

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.