Achnanthidium minutissimum

(Kütz.) Czarn. 1994      Category: Monoraphid
BASIONYM: Achnanthes minutissima Kütz. 1833

Achnanthidium latecephalum


Achnanthidium pyrenaicum

LM scalebar = 10 µm = 80 pixels.


Contributor: Marina Potapova - May 2009
Length Range: 6-21 µm
Width Range: 1.5-3.3 µm
Striae in 10 µm: 25-35


Cells are solitary or in very short chains, often attached to substrate by a stalk. Frustules are monoraphid with a concave raphe valve and convex rapheless valve. Valves are linear-lanceolate with slightly drawn-out or slightly capitate ends, 1.5-3.3 µm wide, 5.6-20.8 µm long. Central external raphe ends are simple, terminal raphe fissures are short, almost straight, or absent. Internally, the central raphe ends are turned in opposite directions. Striae are radiate throughout both valves, 25-35 in 10 µm. Striae consist of one row of areolae. The striae are often interrupted in the central part of raphe valve to form a symmetrical or asymmetrical fascia. One row of elongated areolae is present on the valve mantle. External areolae openings of areolae vary in shape from circular to transapically elongated slits. Internal openings of the areolae are elliptical, occluded by hymens perforated by small pores. Girdle bands are plain, open.

Original Description

Basionym: Achnanthes minutissima
Author: Kütz. 1833
Length Range: µm
Striae in 10 µm:

Original Description

Stipite brevissimo; corpusculis minutissimis parum curvatis lutescentibus, e frustulis plerumque binis constitutis.

Original Images

Cite This Page:
Potapova, M. (2009). Achnanthidium minutissimum. In Diatoms of the United States. Retrieved April 23, 2018, from

Species: Achnanthidium minutissimum

Contributor: Marina Potapova

Reviewer: Sam Rushforth


Czarnecki, D.B. (1994). The Freshwater Diatom Culture Collection at Loras College, Dubuque, Iowa. Kociolek, J.P. (ed.) Proceedings of the 11th International Diatom Symposium, California Academy of Sciences, San Francisco, CA, p. 155-173.

Kützing, F.T. (1833). Synopsis Diatomacearum oder Versuch einer systematischen Zusammenstellung der Diatomeen. Linnaea 8(5): 529-620, pls. XIII-XIX.

Potapova, M. and Hamilton, P. B. (2007). Morphological and ecological variation within the Achnanthidium minutissimum (Bacillariophyceae) species complex . Journal of Phycology 43: 561-575. 10.1111/j.1529-8817.2007.00332.x

Links & ID's

Index Nominum Algarum (INA)

Transfer INA
Original INA

California Academy of Sciences (CAS)

Achnanthidium minutissimum CAS

NCBI Genbank Taxonomy

Achnanthidium minutissimum NCBI

North American Diatom Ecological Database (NADED)

NADED ID: 1010

Autecology Discussion

short mucilaginous stalks or pads

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

Achnanthidium minutissimum

EMAP Response Plots

Achnanthidium minutissimum

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.