Kobayasi 1997 Category: Monoraphid
BASIONYM: Achnanthidium latecephalum Kobayasi 1997
Contributor: Marina Potapova - August 2010
Length Range: 10-16 µm
Width Range: 3.5-3.9 µm
Striae in 10 µm: 20-26 in the center valve, 35-40 at the ends
Valves are linear-lanceolate with broadly rostrate or subcapitate ends. The raphe valve is concave and the rapheless valve is convex.Both valves possess a linear axial area, which widens slightly in the middle portion of the valve. No central area is present on either valve. The striae are parallel or very slightly radiate throughout both valves. Striae density on both valves is 20-26 in 10 µm in the middle and 35-40 in 10 µm at the apices. 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. Short marginal striae are often present in the middle portion of both valves. The raphe is straight, filiform. The terminal raphe fissures are hooked towards the same side of the valve and are slightly expanded at the ends. Externally, the central raphe ends are teardrop-shaped. Internally, the central raphe ends curve to opposite sides.
Basionym: Achnanthidium latecephalum
Author: Kobayasi 1997
Length Range: 10-18 µm
Width Range: 4.0-4.5 µm
Striae in 10 µm: 18-20 in center raphe valve, ca 22 in center rapheless valve, ca 34 at the ends
Valves linear-lanceolate with broadly capitate or rostrate ends, 10-18 μm long, 4.0-4.5 μm wide. Raphid valve: raphe straight and thread-like with slightly dilated central raphe endings somewhat distant from each other, and gently curved terminal fissures; axial area narrowly lanceolate, transapical striae slightly radiate, alternatively long and short in the middle, 18-20 in 10 μm, almost parallel near the ends, ca 34 in 10 μm; puncta forming striae invisible. Araphid valve: axial area linear lanceolate, transapical striae slightly radiate and occasionally having a short stria inserted in the middle, ca 22 in 10 μm, almost parallel near the ends, ca 34 in 10 μm; puncta forming the striae are invisible.
Kobayasi, H. (1997). Comparative studies among four linear-lanceolate Achnanthidium species (Bacillariophyceae) with curved terminal raphe endings. Nova Hedwigia 65: 147-163.
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
Rimet, F., Tudesque, L., Peeters, V., Vidal, H., & Ector, L. (2003). Assemblages-types de diatome´es benthiques des rivie`res non-pollue´es du bassin Rhoˆ ne-Me´diterrane´e-Corse (France). Bulletin de la Socie´te´ des Sciences Naturelles de l’Ouest de la France, 2e`me supple´ment hors se´rie, 272–287.