Stentor Oken, 1815 ,
Class Polyhymenophora Jankowski, 1967: Subclass Spirotricha Butschli, 1889: Order Heterotrichida Stein, 1859: Suborder Heterotrichina Stein, 1859: Family Stentoridae Canes, 1863 (ref. ID; 4798)

[ref. ID; 2014]
Highly contractile body which is trumpet-shaped or cylindrical when extended. Species in the genus tend to be large (up to 2 mm long). The narrower end of the body may be attached to the substratum by a temporary holdfast and the sedentary habit is its usual way of life. In some species the body may be partly encased in a mucilaginous lorica. Stentor may also detach from the substratum and swim freely when the animals adopt an oval to pyriform shape. The body covered by a continuous coat of cilia. There is a conspicuous peristomial field of cilia at the wider anterior end of the body and this is bordered and almost enclosed by a system of adoral membranelles spiraling clockwise to the cytostome. Single contractile vacuole with 2 canals. The macronucleus may be spherical or an elongate central mass in smaller species but is usually moniliform in the larger ones. Pigmentation granules (green, pink, blue or violet) commonly found in several species. Most easily confused with Parastentor which has contractile tentacle-like structures.
Quote; Colin R. Curds, Michael A. Gates and David McL. Roberts "British and other freshwater ciliated protozoa Part II Ciliophora: Oligohymenophora and Polyhymenophora" Cambridge University Press, 1983 (ref. ID; 2014)

Stentor amethystinus Leidy, 1880 (ref. ID; 1621, 1629, 4610, 4613) reported year? (ref. ID; 1618, 3698)
Syn; Stentor niger Roux-Penard (ref. ID; 1621)
Description; Habitually pyriform (contracted); amethyst-blue; with zoochlorellae; macronucleus oval. (ref. ID; 1618)
Measurements; 300-600 um long. (ref. ID; 1618)
Stentor barretti Barrett, 1870 (ref. ID; 4689 redescribed paper) or Kent (ref. ID; 1621) reported author and year? (ref. ID; 4610)
See; Stentor roeseli (ref. ID; 1621)
Description; S. barretti is easily recognised by its elongated, cylindrical lorica which measures up to 1 mm long and 100 um in diameter. The lorica stands erect and is fixed to the substrate by its posterior end. At its anterior end there is an aperture through which the zooid is able project for a distance of up to 0.7 mm giving an overall length of 1.7 mm. If stimulated, the animal quickly contracts back inside its lorica. The main body of S. barretti is colourless and measures up to 1 mm long x 25-30 um wide when fully extended. It is attached by its posterior end via a special attachment organelle, while the anterior end is dominated by a highly distinctive frontal field. Both of these structures are fully described below. The body is covered by alternating longitudinal stripes of two kinds; bands of colourless granules forming narrow stripes and between these, broader clear stripes which bear the rows of somatic cilia. The somatic cilia measure 10-12 um in length and are distributed all over the body. Also present on the body surface are several long, stationary, spine-like sensory cilia. Usually these sensory cilia are in bundles of two or three but occasionally solitary forms were also observed. They are about three times longer than the somatic cilia, measuring 30-35 um, in length. The distribution of sensory cilia over the body is somewhat irregular, being more densely packed in the anterior region, were they lie between 15 and 20 um apart, and more widely spaced in the posterior region, 20-30 um apart. Using Nomarski optics, it was possible to observe the macronucleus which is sinuous and elongate with several constrictions along its length and lies longitudinally in the body. It stretches almost the entire length of the animal from the frontal field to just above the attachment organelle. There is a single contractile vacuole at the anterior end of the cell. (ref. ID; 4689)
[Frontal field] The single most distinctive feature of S. barretti is the frontal field which is typically bilobate with one lobe horizontal to the main axis of the cell and one vertical. The whole area measures up to 180 um across and its surface is furnished with several concentrically arranged stripes. These stripes are granular and unpigmented and run parallel to the adoral zone of membranelles (AZM). The AZM winds anticlockwise around the edge of the frontal field before passing down into the buccal cavity which lies on the left hand side of the cell, near to the junction of the two lobes. As well as the strongly vibratile AZM, several sensory cilia are also present around the edge of the frontal field. These are fairly evenly spaced at intervals of 12-15 um. (ref. ID; 4689)
[Attachment cord] The body of S. barretti is anchored by means of a cord-like attachment organelle. This attachment cord is long (up to 500 um), slender (3 um in diameter) and connects the posterior end of the animal to the base of the lorica. At its junction with the cord, the cell is truncated while the cord is slightly flared into the form of a cone. The cord is noncontractile and when the main body of the organism contracts, the cord is simply pushed down to the bottom of the lorica. During this process the cord folds and coils in a somewhat random fashion but its overall length remains the same. Ultrastructural details and the mode of secretion of the cord are not known. When S. barretti vacates its lorica as a response to unfavourable environmental conditions, the main body of the animal contracts and begins to rotate. This causes the cord to twist and coil. As the spinning continues the somatic cilia in the posterior region begin to beat actively and within a few minutes, sufficient shear force is built up to enable the organism to break free leaving the twisted cord at the bottom of the lorica. The free-swimming animal is typically truncated at this posterior end while the frontal field at the anterior and remains partially contracted. Usually, the organism then circles around the outside of its old lorica several times before swimming off to another environment. (ref. ID; 4689)
[Lorica] Once S. barretti has settled on a substrate it immediately begins to secrete a new lorica. Initially the lorica is smooth, gelatinous and transparent but when feeding commences, particles from the environment are added to give it an opaque, granular appearance. At this stage only particles of 5-8 um in diameter are employed. They are collected by the beating action of the AZM and travel around the frontal field as far as the buccal cavity. From here they are directed over the edge of the frontal field and are swept down the outside of the animal, probably as a result of the beating action of the somatic cilia. Eventually they reach the anterior end of the lorica where they are added to the lorica wall. As the lorica gets older, larger particles such as sand grains, diatom frustules and testate amoebae shells are also incorporated and the lorica attains its characteristic elongated cylindrical shape. (ref. ID; 4689)
Remarks; In 1870 Charles Barrett isolated a loricate Stentor from the River Thames at Moulsford, Berkshire, England which he was unable to correlate with any of the previously described species. The main distinguishing characters listed by Barrett (1870) were that it possessed an ear-shaped frontal field with two lobes, one horizontal to the major axis of the cell and one vertical; numerous long, stationary cilia (i.e. sensory cilia) all over the body surface including the frontal field; and an opaque, highly elongated, cylindrical lorica. He provisionally named this animal Stentor barretti pending further investigation. Kent (1880-1882) subsequently confirmed S. barretti to be a distinct species but thereafter, it has never been redescribed. In his taxonomic review of the ciliates, Kahl (1930-1935) synonymysed S. barretti with the more familiar S. roeseli Ehrenberg, 1835 and in the most recent review of the genus, Tartar (1961) also failed to recognise S. barretti as a separate species. (ref. ID; 4689)
Stentor coeruleus Ehrenberg, 1830 (ref. ID; 1621, 1629, 2245, 3116, 4070) reported year? (ref. ID; 1219, 1618, 3342, 3343, 4056) or (Pallas, 1766) Ehrenberg (1831) (ref. ID; 4488, 4610) reported author and year? (ref. ID; 191, 3292, 4550, 4675, 5969)
Syn; Brachionus stentoreus var. coerulei Pallas, 1766 (ref. ID; 4610); Stentor attenuatus Maskell, 1888 (ref. ID; 1621)
Description; Trumpet-shaped when extended, after contraction more or less spherical; striking blue color (due to the pigment "stentorin"); uniform ciliation all over the body, a small number of sensory bristles; adoral zone of membranelles extends in a spiral form around the anterior pole of the body; the buccal area itself is equipped with rows of smaller cilia; macronucleus rosary-shaped; contractile vacuole in the anterior part left behind the cytopharynx with long canals directed in posterior and anterior direction. (ref. ID; 1219)
Anterior end greatly expanded; the beautiful blue color is due to a pigment, stentorin, lodged in interstriation granules; macronucleus moniliform; fresh water. (ref. ID; 1618)
Measurements; Length 1-2 mm (fully extended). (ref. ID; 1219, 1618, 3343)
270-700 um. (ref. ID; 3342)
Stentor igneus Ehrenberg, 1838 (ref. ID; 1308, 1621, 1629, 2245, 4488, 4610, 4730) reported year? (ref. ID; 1618, 3698)
Description; Rose-colored or colorless; macronucleus oval; ciliation uniform. (ref. ID; 1618)
Measurements; 200-400 um long. (ref. ID; 1618)
Stentor introversus Tartar, 1958 (ref. ID; 1618, 4610)
Description; Adoral zone retractable; blue-green; with 70-90 ectoplasmic stripes of blue-green granules; macronucleus moniliform; fresh water. (ref. ID; 1618)
Measurements; 103-306 (up to 450) by 135-288 um. (ref. ID; 1618)
Stentor mulleri (Bory St. Vincent) (ref. ID; 1618) or (Bory St. Vincent, 1824) Ehrenberg, 1838 (ref. ID; 1621)
Description; Colorless; with zoochlorellae; anterior end expanded; posterior portion drawn out into stalk, often in a gelatinous tube; on body surface 3-4 longer and stiff cilia grouped among cilia; macronucleus moniliform. (ref. ID; 1618)
Measurements; 2-3 mm long. (ref. ID; 1618)
Stentor multiformis (O. F. Muller, 1786) (ref. ID; 4798) reported year? (ref. ID; 1618), (Muller, 1786) Ehrenberg, 1838 (ref. ID; 4488, 4610) or (O. F. Muller, 1786) Stein (ref. ID; 1621, 1629)
Syn; Vorticella multiformis O. F. Muller, 1786 (ref. ID; 4610)
Description; Dark blue to bluish green; anterior end not expanded; macronucleus oval. (ref. ID; 1618)
Measurements; 150-200 um long. (ref. ID; 1618)
Stentor niger (O. F. Muller) (ref. ID; 1618), (O. F. Muller, 1773) Ehrenberg, 1831 (ref. ID; 4610) or (O. F. Muller, 1786) Ehrenberg, 1838 (ref. ID; 1621, 1629) reported author and year? (ref. ID; 191, 4115)
Syn; Stentor pediculatus Fromentel (ref. ID; 1621); Vorticella nigra O. F. Muller, 1773 (ref. ID; 4610)
Description; Yellowish or brown; macronucleus oval. (ref. ID; 1618)
Measurements; 200-300 um long. (ref. ID; 1618)
Stentor polymorphus (Ehrenberg) (ref. ID; 4111), (O. F. Muller, 1773) (ref. ID; 3116) reported year? (ref. ID; 1618), (O. F. Muller, 1773) Ehrenberg, 1830 (ref. ID; 4610), (O. F. Muller, 1773) Ehrenberg, 1838 (ref. ID; 1219, 1629, 2245, 4488) reported year? (ref. ID; 5462) or (O. F. Muller) Ehrenberg-Stein (ref. ID; 3690) reported author and year? (ref. ID; 191, 3292)
Syn; Vorticella polymorpha O. F. Muller, 1773 (ref. ID; 4610)
Description; Shape very similar to that of S. coeruleus, but colorless and the body filled with symbiotic zoochlorellae; macronucleus rosary-shaped; usually without a lorica. (ref. ID; 1219)
Colorless; with symbiotic Chlorella. Macronucleus beaded; anterior end expanded. (ref. ID; 1618)
[Resting cyst] Elongate macronucleus and spherical contractile vacuole in a granular cytoplasm with alternate green and colorless longitudinal stripes as in the trophic stage. (ref. ID; 4111)
Measurements; Length 1-2 mm (fully extended). (ref. ID; 1219, 1618)
Stentor pyriformis Johnson (ref. ID; 1618)
Measurements; When expanded 500 um long; anterior end 200 um in diameter. (ref. ID; 1618)
Stentor roeseli Ehrenberg, 1835 (ref. ID; 1621, 1629, 1896, 2245, 3116) reported year? (ref. ID; 1219, 1618, 3342, 3343), roeselii Ehrenberg, 1835 (ref. ID; 4610) reported author and year? (ref. ID; 191)
Syn; Stentor barretti Kent (ref. ID; 1621); Stentor gracilis Maskell, 1886 (ref. ID; 1621); Stentor viridis Ghosh, 1921 (ref. ID; 1621) reported year? (ref. ID; 3342, 3343)
Description; Generally features similar to those of S. coeruleus, but colorless or slightly yellowish, and with a long, band-like nucleus; group of longer cilia (sensory bristles) between the uniform ciliation; posterior portion often housed in a mucilaginous lorica or tube. (ref. ID; 1219)
Anterior end expanded; body surface with groups of longer cilia; posterior portion drawn out and often housed in a gelatinous tube; macronucleus long band-form. (ref. ID; 1618)
Measurements; Length 0.5-1.0 mm (fully extended). (ref. ID; 1219, 1618)
380-450 um. (ref. ID; 3342)
Length 1200 um, length of lorica 500 um. (ref. ID; 3343)