Platessa conspicua

(A.Mayer) Lange-Bert. in Krammer and Lange-Bert. 2004      Category: Monoraphid
BASIONYM: Achnanthes conspicua A.Mayer 1919
SYNONYM(S): Planothidium conspicuum (Mayer) Aboal in Aboal, Alvarez-Cobelas, Cambra and Ector 
REPORTED AS: Achnanthes pinnata (Patrick and Reimer 1966) 

Platessa bahlsii


Platessa hustedtii

LM scalebar = 10 µm = 80 pixels.


Contributor: Marina Potapova - December 2010
Length Range: 7-18 µm
Width Range: 3.6-5.4 µm
Striae in 10 µm: 12-16


Valves are linear-elliptical. The raphe valve has a narrow axial area and transversely rectangular central area that reaches both valve margins. The rapheless valve has a lanceolate axial area and no distinct central area, though the two middle striae may be slightly more distant from each other than less central striae. The raphe is straight, with slightly expanded terminal and central ends, without terminal fissures. Internally (SEM), the central raphe ends curve toward opposite sides. Striae are almost parallel in the valve center, but become strongly radiate approaching the poles of both valves, biseriate, 12-16 in 10 µm. A single row of areolae exists on the valve mantle, with each areola opposed to a biseriate stria. The external and internal openings of the areolae are circular or somewhat angular, isodiametric.

Original Description

Basionym: Achnanthes conspicua
Author: A.Mayer 1919
Length Range: 10-12 µm
Width Range: 5.5 µm
Striae in 10 µm: 13-14

Original Description

A. valvis prorsus ovalibus finibus rotundatis, 0,01—0,012 mm longis, 0,0055 mm latis; striis paene parallelis, ad fines subradiantibus, duobus mediis utriusque valvae perspicue distinctis, ab interiore parte ad exteriorem subappropin-quantibus, interdum una stria tenuissima in valva inferiore inter strias medias magis distantes intercalata, striis validis, 13—14 intra 0,01 mm

Original Images

Cite This Page:
Potapova, M. (2010). Platessa conspicua. In Diatoms of the United States. Retrieved April 18, 2018, from

Species: Platessa conspicua

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.

Krammer, K. and Lange-Bertalot, H. (2004). Bacillariophyceae 4. Teil: Achnanthaceae, Kritische Erganzungen zu Navicula (Lineolatae), Gomphonema Gesamtliteraturverzeichnis Teil 1-4 [second revised edition]. In: H. Ettl et al., Suesswasserflora von Mitteleuropa. Spektrum Akademischer Verlad Heidelberg, 468 pp.

Mayer, A. (1919). Bacillariales von Reichenhall und Umgebung. Kryptogamische Forschungen herausgegeben von der Kryptogamenkommission der Bayerischen Botanischen Gesellschaft zur Erforschung der heimischen Flora 1(4):191-216.

Links & ID's

Index Nominum Algarum (INA)

California Academy of Sciences (CAS)

Platessa conspicua CAS

North American Diatom Ecological Database (NADED)

NADED ID: 2508001

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

Platessa conspicua

EMAP Response Plots

Platessa conspicua

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.