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Achnanthidium atomus

(Hust.) Monnier, Lange-Bert. and Ector 2004      Category: Monoraphid
BASIONYM: Achnanthes atomus Hust. 1937

Achnanthidium alpestre


Achnanthidium deflexum

LM scalebar = 10 µm = 80 pixels.


Contributor: Marina Potapova - May 2010
Length Range: 10-21 µm
Width Range: 3-3.5 µm
Striae in 10 µm: 28-30 in raphe valve, 22-25 in rapheless valve


Valves are elliptical to linear-ellitical. The raphe valve is concave with a linear axial area, which widens slightly in the middle portion of the valve. The raphe is straight without the terminal raphe fissures. The central raphe ends are simple externally, not expanded. Internally, the central raphe ends curve toward opposite sides. The striae are strongly radiate throughout the raphe valve, 28-30 in 10 µm in the middle and up to 40 in 10 µm at the apices. In the middle of the valve the striae are interrupted to form a transverse fascia. The rapheless valve is convex. It has a narrow, linear axial area and no central area. Striae are parallel throughout the rapheless valve, becoming slightly radiate at the apices, 22-25 in 10 µm. The external openings of the areolae are transapically elongated to almost isodiametric. Striae have a maximum of 4-5 areolae on the valve face and one areola on the margin of both rapheless and raphe valves.

Original Description

Basionym: Achnanthes atomus
Author: Hust. 1937
Length Range: 7-16 µm
Width Range: 2.5-3 µm
Striae in 10 µm: 28-30 on raphe valve, 22-25 on rapheless valve

Original Description

Schalen schmal linear, selten gegen die Enden etwas lanzettlich verschmälert, an den Polen stumpf gerundet, 7-16 μ lang, 2,5-3 μ breit. Raphenschale mit gerade, fadenförmiger Raphe, Axialarea sehr eng, Zentralarea eine bis an den Rand reichende Querbinde von wechselnder Breite. Transapicalstreifen kräftig, durchweg ziemlich stark radial, 28-30 in 10μ. Raphelose Schale mit sehr enger Pseudoraphe, ohne Zentralarea, Transapicalstreifen senkrecht zur Mittellinie oder nur wenig radial, gröber als auf der Rapheschale, 22-25 in 10 μ, zart aber deutlich punktiert.

Original Images

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

Species: Achnanthidium atomus

Contributor: Marina Potapova

Reviewer: Sarah Spaulding


Hustedt, F. (1937). Systematische und ökologische Untersuchungen über die Diatomeen-Flora von Java, Bali und Sumatra nach dem Material der Deutschen Limnologischen Sunda-Expedition. Archiv für Hydrobiologie, Supplement 15: 187-295.

Monnier, O., Lange-Bertalot, H., Rimet, F., Hoffman, L., and Ector, L. (2004). Achnanthidium atomoides sp. nov., a new diatom from the Grand-duchy of Luxembourg. Vie et Milieu 54:127-136.

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

Links & ID's

Index Nominum Algarum (INA)

Original INA

California Academy of Sciences (CAS)

Achnanthidium atomus CAS

North American Diatom Ecological Database (NADED)

NADED ID: 1037

Autecology Discussion