Planothidium delicatulum

(Kütz.) Round and Bukht. 1996      Category: Monoraphid
BASIONYM: Achnanthidium delicatulum Kütz. 1844

REPORTED AS: Achnanthes delicatula  (Cleve and Grunow 1880) 

Planothidium biporomum


Planothidium dubium

LM scalebar = 10 µm = 80 pixels.


Contributor: Marina Potapova - December 2010
Length Range: 12-20 µm
Width Range: 4.7-7.5 µm
Striae in 10 µm: 13-15


Valves are lanceolate with protracted subrostrate apices The raphe valve has a transversely elliptical or rectangular central area. The rapheless valve has a linear-lanceolate axial area. The features of the middle of the rapheless valve are variable across populations: valves may lack a distinguishable central area, or two middle striae on one side of the axial area can be slightly more distant from one another than from the other striae. The raphe is straight with expanded external proximal ends. The striae are strongly radiate on the raphe valve and slightly radiate on the rapheless valve.

Note that this concept of P. delicatulum more or less corresponds to the “Sippen mit schnabelartig vorgezogenen Polen” in Krammer & Lange-Bertalot (1991, figs 39:6-14), while the Neotype of Achnanthes delicatula may represent a similar, but different species (Figs 39: 1-5 in Krammer & Lange-Bertalot 1991). Further work is needed to clarify taxonomy of this species complex.

Original Description

Basionym: Achnanthidium delicatulum
Author: Kütz. 1844
Length Range: 16 µm
Striae in 10 µm:

Original Description

A. a latere secundario ven-tricosum, apicibus productis.

Original Images

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

Species: Planothidium delicatulum

Contributor: Marina Potapova

Reviewer: Sarah Spaulding


Kützing, F.T. (1844). Die kieselschaligen Bacillarien oder Diatomeen. Nordhausen. 152 pp., 30 pls.

Round, F. E. and Bukhtiyarova, L. (1996). Four new genera based on Achnanthes (Achnanthidium) together with a re-definition of Achnanthidium. Diatom Research 11: 345-361.

Links & ID's

Index Nominum Algarum (INA)

Original INA

California Academy of Sciences (CAS)

Planothidium delicatulum CAS

North American Diatom Ecological Database (NADED)

NADED ID: 155009

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 delicatulum

EMAP Response Plots

Planothidium delicatulum

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.