| Stentor roeselii | |
|---|---|
| |
| Stentor roeselii | |
Scientific classification
| |
| Domain: | Eukaryota |
| Clade: | Diaphoretickes |
| Clade: | SAR |
| Clade: | Alveolata |
| Phylum: | Ciliophora |
| Class: | Heterotrichea |
| Order: | Heterotrichida |
| Family: | Stentoridae |
| Genus: | Stentor |
| Species: | S. roeseli
|
| Binomial name | |
| Stentor roeseli Ehrenberg 1835
[1]
| |
Stentor roeselii is a free-living ciliate species of the genus Stentor, in the class Heterotrichea. It is a common and widespread protozoan, found throughout the world in freshwater ponds, lakes, rivers and ditches. [2] [3]
Appearance and Characteristics
S. roeselii is found in still or slow-moving bodies of water, where it feeds on bacteria, flagellates, algae, and other ciliates. When feeding, the cell is fixed in place ( sessile), attached by a posterior "holdfast" organelle to a firm surface such as plant stem or submerged detritus. Attached specimens are trumpet-shaped, and very contractile. When swimming freely, cells are compactly ovoid. Fully stretched out specimens are usually between 500 and 1200 micrometres in length, but size is extremely variable. [4] [5]
It is a colourless species, with no pigmentation in the cell cortex. The body of the organism is covered with 40-80 longitudinal rows of cilia, and the oral region is encircled by a long spiraling row of specialized ciliary structures called membranelles which are mainly used for brushing prey into the cell mouth ( cytostome). The cytoplasm is transparent, and contains no symbiotic algae ( zoochlorellae). When the organism is fully extended, its macronucleus is long and worm-like. In contraction, the macronucleus may show distinct nodules separated by constricted areas, giving it the appearance of a string of beads. Cells have a single contractile vacuole, located to the left of the cell mouth ( cytostome). [4]
The tail end of feeding organisms may be surrounded by a loose, mucilaginous lorica filled with debris and excreted matter. The presence or absence of this lorica is not considered a diagnostic character of the genus. [3]
Although only a single-celled ciliate, Stentor roeselii expresses a sort of "behavioral hierarchy" and can 'change its mind' if its response to an irritant does not relieve the irritant, implying a very speculative sense of 'cognition'. [6] [7]
References
- ^ "Protist Images: Stentor roeseli". Protist.i.hosei.ac.jp. Retrieved 2010-08-24.
- ^ Bick, Hartmut (1972). Ciliated Protozoa. Geneva: World Health Organization. pp. 142–143.
- ^ a b Foissner, W.; Wölfl, S. (1994). "Revision of the genus Stentor Oken (Protozoa, Ciliophora) and description of S.araucanus nov. spec, from South American lakes". Journal of Plankton Research. 16 (3): 255–289. doi: 10.1093/plankt/16.3.255. ISSN 0142-7873.
- ^ a b Foissner, Wilhelm; et al. (1992). Taxonomische und okologische Revision der Ciliaten des Saprobiensystems, Band II. Munich: Bayerisches Landesamt für Wasserwirtschaft. pp. 374–381.
- ^ Serrano, Susana; Arregui, Lucia; Perez-Uz, Blanca; Calvo, Pilar; Guinea, Almudena (2008-02-01). Guidelines for the Identification of Ciliates in Wastewater Treatment Plants. IWA Publishing. ISBN 9781843391715.
- ^ "Can a single-celled organism 'change its mind'? New study says yes". phys.org. Retrieved 2019-12-06.
- ^ Tang SKY; Marshall, W. F. (22 October 2018). "Cell learning". Current Biology. 28 (20): R1180–R1184. doi: 10.1016/j.cub.2018.09.015. PMC 9673188. PMID 30352182. S2CID 53031600.
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