Psammothidium semiapertum
(Hustedt) Aboal in Aboal, Alvarez-Cobelas, Cambra and Ector 2003 Category: Monoraphid
BASIONYM: Cocconeis semiaperta Hustedt 1945
SYNONYM(S): Achnanthes hintzii Lange-Bertalot and Krammer
LM scalebar = 10 µm = 80 pixels.
Observations
Contributor: Marina Potapova - August 2011
Length Range: 8.5-10.4 µm
Width Range: 4.4-5.2 µm
Striae in 10 µm: 22-24
Description
Valves are elliptic. Raphe valve has a narrow linear axial area and a transversely rectangular central area. The raphe is filiform and straight with slightly expanded, almost straight or very slightly deflected external distal and proximal ends. Internal proximal raphe ends are deflected to opposite sides. Internal distal ends terminate in small helictoglossae. The apheless valve has a narrow linear axial area and a transversely rectangular central area that may be symmetric, or slightly asymmetric. Striae are uniseriate. Areolae are isodiametric and number 25 in 10 μm. There are 5-7 areolae in each central stria.
Note that specimens from the type material from Europe have slightly larger valves (about 6 μm wide) and more distinctly asymmetric central area on rapheless valve than specimens from the U.S. This species is, however, extremely rare in the type material and at present it is not possible to determine whether specimens from Europe and North America belong to the same species.
Original Description
Basionym: Cocconeis semiaperta
Author: Hustedt 1945
Length Range: 10 µm
Width Range: 6 µm
Striae in 10 µm: 25
Original Description
Cocconeis semiaperta n. sp. - Schalen breit elliptisch, um 10 µ lang, etwa 6 µ breit. Raphenschale mit gerader, fadenförmiger Raphe, Axialarea sehr eng, Zentralarea einseitig bis fast an den Schalenrand erweitert. Transapikalstreifen durchweg radial, etwa 25 in 10 µ zart punktiert, Punkte in unregelmäßig welligen Längslinien, die annähernd in derselben Entfernung stehen wie die Transapikalstreifen. Raphenlose Schalen mit sehr schmal lanzettlicher Axialarea, Zentralarea einseitig bis an den Schalenrand er- weitert, Struktur der Zellwand wie an der Raphenschale.Taf. XXXIX Abb. 1-3. Plitvicer Seengebiet, sehr selten in einem Wasserfall und an litoraler Chara. - Besonders charakteristisch durch die Form der Zentralarea und mit keiner anderen Art zu verwechseln.
Original Images
Cite This Page:
Potapova, M. (2011). Psammothidium semiapertum. In Diatoms of the United States. Retrieved May 23, 2013, from http://westerndiatoms.colorado.edu/taxa/species/psammothidium_semiapertum
Species: Psammothidium semiapertum
Contributor: Marina Potapova
Reviewer: Sarah Spaulding
Image Credit: Marina Potapova
- Valves elliptic
- Striae 22-24 in 10 µm
- Areolae 25 in 10 µm
- Rapheless valve may have asymmetric central area
Valves are elliptic. Both valves have narrow linear axial areas and transversely rectangular central areas. The central area on the rapheless valve may be asymmetric. The raphe is filiform and straight. There are 25 areolae in 10 μm along the stria.
Compare
Psammothdium semiapertum differs from P. pennsylvanicum by lower areola density (25 vs 35-40 in 10 μm).
Psammothidium pennsylvanicum
Citations
Aboal, M., Alvarez-Cobelas, M., Cambra, J. and Ector, L. (2003). Floristic list of non marine diatoms (Bacillariophyceae) of Iberian Peninsula, Balearic Islands, and Canary Islands. Updated taxonomy and bibliography. In: A. Witkowski (ed.), Diatom Monographs. A.R.G. Gantner Verlag K.G., 4: 639 pp.
Krammer, K. and Lange-Bertalot, H. (2004). Bacillariophyceae 4. Teil: Achnanthaceae, Kritische Erganzungen zu Navicula (Lineolatae), Gomphonema Gesamtliteraturverzeichnis Teil 1-4 [second revised edition]. In: H. Ettl et al., Suesswasserflora von Mitteleuropa. Spektrum Akademischer Verlad Heidelberg, 468 pp.
Potapova, M. (2012). New species and combinations in monoraphid diatoms (Family Achnanthidiaceae) from North America. Diatom Research 27(1): 29-42. doi:10.1080/0269249X.2011.644636
Links & ID's
Index Nominum Algarum (INA)
California Academy of Sciences (CAS)
North American Diatom Ecological Database (NADED)
NADED ID: 186020