Achnanthidium alpestre

(R.L.Lowe and Kociolek) R.L.Lowe and Kociolek in J.R.Johans. et al. 2004      Category: Monoraphid
BASIONYM: Achnanthes deflexa var. alpestris R.L.Lowe and Kociolek 1984

Achnanthes undulorostrata


Achnanthidium atomus

LM scalebar = 10 µm = 80 pixels.


Contributor: Marina Potapova - August 2010
Length Range: 10-20 µm
Width Range: 3.7-4.4 µm
Striae in 10 µm: 24-28 in the center of raphe valve, 26-32 in the center of rapheless valve, 35-42 at the ends


Valves are linear-lanceolate with subrostrate ends. The raphe valve is concave with a linear axial area, which widens slightly in the middle portion of the valve. The terminal raphe fissures are hooked towards the same side of the valve. The central raphe ends are teardrop-shaped externally and curve to opposite sides internally. The rapheless valve is convex with a narrow, linear axial area widening slightly in the middle. Striae are parallel or very slightly radiate throughout both valves. Striae 24-28 in 10 µm in the middle and 35-42 in 10 µm at the apices of the raphe valve. Striae 26-32 in 10 µm in the middle and 35-40 in 10 µm at the apices of the rapheless valve. The external openings of the areolae are transapically elongated, appearing as narrow slits. Each stria in the middle part of the valve is composed of 4-5 areolae.

Original Description

Basionym: Achnanthes deflexa var. alpestris
Author: R.L.Lowe and Kociolek 1984
Length Range: 9-27 µm
Width Range: 2.5-5 µm
Striae in 10 µm: 19-22 in the center valve, 29-31 at the ends

Original Description

Valves 9-27 μm long, 2.5-5 μm wide, with 19-22 striae in 10 μm at valve center, 29-31 striae in 10 μm at the ends on both the raphe and pseudoraphe valve. Valves linear, with subrostrate ends. Smaller specimens becoming rounded with no distinct ends. Raphe filiform, with distal raphe ends deflecting in the same direction. Differs from the nominate variety in the widely spaced median striae.

Original Images

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

Species: Achnanthidium alpestre

Contributor: Marina Potapova

Reviewer: Sarah Spaulding


Johansen, J.R., Lowe, R., Gomez, S.R., Kociolek, J.P. and Makosky, S.A. (2004). New algal species records for the Great Smoky Mountains National Park, U.S.A., with an annotated checklist of all reported algal species for the park. Archiv für Hydrobiologie Supplement 150: 17-44.

Lowe, R.L. and Kociolek, J.P. (1984). New and rare diatoms from Great Smoky Mountains National Park. Nova Hedwigia 39(3-4): 465-476.

Ponader, K. and Potapova, M. (2007). Diatoms from the genus Achnanthidium in flowing waters of the Appalachian Mountains (North America): Ecology, distribution and taxonomic notes. Limnologica - Ecology and Management of Inland Waters 37: 227-241 . 10.1016/j.limno.2007.01.004

Potapova, M. and Ponader, K.C. (2004). Two common North American diatoms, Achnanthidium rivulare sp. nov. and A. deflexum (Reimer) Kingston: morphology, ecology and comparison with related species. Diatom Research 19(1): 33-57.

Links & ID's

Index Nominum Algarum (INA)

Transfer INA

California Academy of Sciences (CAS)

Achnanthidium alpestre CAS

North American Diatom Ecological Database (NADED)

NADED ID: 1041

Autecology Discussion