Planothidium
Round et Bukhtiyarova 1996 Category: Monoraphid
TYPE SPECIES: Planothidium lanceolatum (Brébisson) Round et Bukhtiyarova
Image Credit: Eduardo Morales, Marina Potapova, Ditmar Metzeltin
CLASS: Bacillariophycideae
ORDER: Achnanthales
FAMILY: Achnanthidiaceae
- Raphe valve with radiate striae
- Striae multiseriate
- Rapheless valve may have asymmetrical central area
- Rapheless valve may have hood
Frustules of Planothidium are heterovalvar, with slightly concave raphe valve and convex rapheless valve. Valves are elliptic to lanceolate, with rounded, rostrate or capitate apices. The striae are multiseriate. The raphe valve possess radiate striae and a prominent raphe. The terminal raphe fissures are deflected unilaterally.
Many Planothidium species, but not all, possess an asymmetrical central area on the rapheless valve. Internally, this central area bears either a rimmed depression, or a hood. Note that alternate terms for the hood are "cave" and "cavum". The difference between the rimmed depression and hood was not recognized until the structures were examined under SEM. Previously, the structures were termed ‘hufeisenförmige Fleck” in German, or “hoof-mark” or "horseshoe structure" in English.
Cells have an adnate growth habit, in which they are attached by the raphe valve face to the substrata. The genus was split from Achnanthidium by both Round and Bukhtiyarova (1996) and Lange-Bertalot (1997). Details of sexual reproduction in P. lanceolatum are described in Geitler (1977).
Cite This Page:
Spaulding, S., Edlund, M., and Metzeltin, D. (2009). Planothidium. In Diatoms of the United States. Retrieved May 19, 2013, from http://westerndiatoms.colorado.edu/taxa/genus/Planothidium
Contributor: Sarah Spaulding | Mark Edlund | Ditmar Metzeltin - January 2009
Reviewer: Marina Potapova
Citations
Compère, P. and Van de Vijver, B. (2009). Planothidium engelbrechtii (Cholnoky) Round & Bukhtiyarova; identity and lectotypification. Fottea 9(2): 187-192.
Geitler, L. (1977). Entwicklungsgeschichtliche Eigentümlichkeiten einiger Achnanthes-Arten (Diatomeae). Plant Systematics and Evolution 126:277-392.
Geitler, L. (1980). Zellteilung und Bildung von Innenschalen bei Hantzschia amphioxys und Achnanthes coarctata. Plant Systematics and Evolution 136:275-286.
Kingston, J.C. (2003). Araphid and Monoraphid Diatoms. In: Freshwater Algae of North America. Ecology and Classification (J.D. Wehr and R.G. Sheath, eds). Elsevier Science pp. 595-636.
Lange-Bertalot, H. (1997). Revision of the genus Achnanthes sensu lato (Bacillariophyceae): Achnantheiopsis, a new genus with the type species A. lanceolata. Archiv fur Protistenkunde 148: 199-208.
Lange-Bertalot, H. and Krammer, K. (1989). Achnanthes eine Monographie der Gattung mit Definition der Gattung Cocconeis and Nachtragen zu den Naviculaceae. Bibliotheca Diatomologica 18, 393 pp. Cramer, Berlin, Stuttgart.
Moss, M.O. and Carter, J.R. (1982). The resurrection of Achnanthes rostrata Ostrup. Bacillaria 5: 147-164.
Noga, T. and Olech, M. (2004). Diatom communities in Moss Creek (King George Island, South Shetland Islands, Antarctica) in two summer seasons: 1995/96 and 2001/02. Oceanological and Hydrological Studies 33: 103-120.
Round, F. E. and Bukhtiyarova, L. (1996). Four new genera based on Achnanthes (Achnanthidium) together with a re-definition of Achnanthidium. Diatom Research 11: 345-361.