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]
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]