Achnanthes inflata

(Kütz.) Grunow 1867      Category: Monoraphid
BASIONYM: Stauroneis inflata Kütz. 1844

Achnanthes felinophila


Achnanthes longboardia

LM scalebar = 10 µm = 40 pixels.


Contributor: David R.L. Burge - July 2012
Length Range: 32-59 µm
Width Range: 13.5–21.1 µm
Striae in 10 µm: 11


Frustules are heterovalvar with a raphe valve and a rapheless valve. The valves are triundulate with the central valve margin wider than the apices, which are broadly rounded and capitate. Both valves are symmetric about the apical and transapical axes. The raphe valve face is concave about the transapical axis. On the raphe valve, the axial area is centered on the apical axis. The axial area is linear but narrows at the distal ends. A distinct transverse fascia is present in the central area. The raphe is slightly reverse lateral with expanded proximal ends. The proximal ends are unilaterally deflected. The distal raphe ends are deflected in the opposite direction. The distinctly uniseriate, punctate striae on the raphe valve are slightly radiate throughout and evenly spaced, 11 in 10 µm. The rapheless valve is convex about the transapical axis and does not have a fascia. On the rapheless valve, the narrow sternum is eccentric and positioned on the margin except where the valve center is expanded. The striae on the rapheless valve are distinctly punctate and have the same density as on the raphe valve. The rapheless valve striae are mostly parallel, tending to convergent and curved near the apices. Areolae on both valves are coarse and distinct, 11-12 in 10 µm. As a result of the concave and convex valve faces, the girdle view of A. inflata gives a recurved shape where the raphe valve valve fasica is on the inside of the curve.

Original Description

Basionym: Stauroneis inflata
Author: Kütz. 1844
Length Range: µm
Striae in 10 µm:

Original Description

  1. STAURONEIS INFLATA. Taf. 30. Fig. 22. (420/1). St. oblonga, media et apicibus late dilatata, bis constricta, late rotundato-truncata. Longet. 1/40 – 1/35’’’. Insel Trinidad; Krüger!

Original Images

Cite This Page:
Burge, D. (2012). Achnanthes inflata. In Diatoms of the United States. Retrieved April 18, 2018, from

Species: Achnanthes inflata

Contributor: David R.L. Burge

Reviewer: Rex Lowe


Burge, D.R.L. (2014). Relations of water quality, land use buffers, and diatom communities of connected depressions within the Cache River Watershed, Arkansas, USA. M.S. Thesis. Arkansas State University, Jonesboro, Arkansas. 141 pp.

Grunow, A. (1867). Reise seiner Majestät Fregatte Novara um die Erde. Botanischer Theil. 1. Algen. Wein, aus der Kaiselich-Königlichen Hof-und Staasdruckerei, pp. 1-104., 11 pls.

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

Patrick, R.M. and Reimer, C.W. (1966). The Diatoms of the United States exclusive of Alaska and Hawaii, V. 1. Monographs of the Academy of Natural Sciences of Philadelphia 13.

Links & ID's

Index Nominum Algarum (INA)

Original INA
Transfer INA

California Academy of Sciences (CAS)

Achnanthes inflata CAS

North American Diatom Ecological Database (NADED)

NADED ID: 2128

Autecology Discussion

Achnanthes inflata was common in epidendric samples from the woody plants Nyssa aquatica and Taxodium distichum (Fig. 2). The trees were sampled in an ephemeral wetland along the Cache River in northeast Arkansas. Other common species in the collection were Eunotia metamonodon, E. pectinalis, and Luticola mutica.

Water chemistry for the site: 22.5C, pH 7.28, conductivity 375 µS, NTU 8.63, dissolved oxygen 5.08 mg/L, NO3 0.345 mg/L, NO2 0.069 mg/L, orthophosphate 0.172 mg/L (Burge 2014).


Frustule in girdle view with two chloroplasts visible. Scale bar = 10 µm

Credit/Source: David Burge

Sample site and substrates in the Cache River, Arkansas, where Achnanthes inflata was collected.

Credit/Source: David Burge

Distribution of Achnanthes inflata in rivers of the continental U.S. based on the National Water Quality Assessment program. Retrieved 16 June 2015.

Credit/Source: USGS BioData

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

Achnanthes inflata

EMAP Response Plots

Achnanthes inflata

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.


- Update to size range.

Image added and text size range expanded to incorporate specimens sampled from Lake Catherine State Park, AR