Stentor Oken, 1815 (ref. ID; 2014, 7228) ,
Class Polyhymenophora: Subclass Spirotricha: Order Heterotrichida: Suborder Heterotrichina (ref. ID; 2014)
Class Polyhymenophora Jankowski, 1967: Subclass Spirotricha Butschli, 1889: Order Heterotrichida Stein, 1859: Suborder Heterotrichina Stein, 1859: Family Stentoridae Canes, 1863 (ref. ID; 4798)

Synonyms Salpistes, Stentorella, Stentorina (ref. ID; 7228)

[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)

[ref. ID; 7228]
Diagnosis; Medium-sized (100 um) to very large (up to 4 mm) heterotrich ciliates, sedentary or freely motile, in the former case attaching themselves by their posterior extremity (holdfast) to submerged aquatic objects, usually secreting a mucilaginous lorica. Body moderately to highly contractile; when swimming and contracted, clavate, pyriform or turbinate; when fix and extended, slenderly to broadly trumpet shaped, i.e. broadly expanded anteriorly, tapering off and attenuate towards the attached posterior extremity. Somatic ciliature holotrichous, in even longitudinal rows, usually supplemented by sparingly scattered hair-like setae ('sensory bristles'). Adoral zone of membranelles at margin of elliptical to circular, rarely bilobate, peristomial bottom, its left-hand extremity or limb spirally involute, forming a small buccal cavity which leads to the cytostome, the right-hand limb free and usually raised considerably above the opposite or left-hand one. Macronucleus vermiform, nodulate, moniliform or composed of one to few spherical masses ('beads'). Contractile vacuole consisting of an anterior circular dilatation, which gives off a horizontal annular branch which underlies the circumference of the peristome, and a canal-like diverticulum which extends towards the posterior extremity of the body. Cortex with stripes of colourless or conspicuously pigmented (red, blue, green, brownish) granules. Some species with symbiotic green algae. Inhabiting mainly freshwater, rarely saltwater or terrestrial biotopes; mostly social, often forming lawn-like covers or water blooms. (ref. ID; 7228)
[Endosymbionts ('zoochlorellae')]: Several Stentor species have apparently stable associations with symbiotic green algae, which belong to the Chlorella vulgaris group according of their physiological and ultrastructural characteristics (Reisser 1984). The symbionts are usually 4-7 um in size and hava a single, cup-shaped chloroplast. They are located either mainly in the ecto-endoplasmic boundary (e.g. S. amethystinus) or scattered through the cytoplasm (e.g. S. polymorphus). Depending on species, size and physiological state, the number of symbionts varies, but usually there are at least some hundreds. Bacterial endosymbionts were recently described by Gortz and Wiemann (1987) in S. multiformis. Their taxonomic value is not known. Microsporidian parasites were found in S. polymorphus and S. roeselii (Gortz 1987). There is a long-lasting debate on whether symbiotic green algae can be used as a species character. I agree with many taxonomists that 'green populations' are usually distinct species because closer examination often reveals more or less pronounced morphological differences to the aposymbiotic congeners [see Foissner (1994) for example]; furthermore, the integration of a symbiotic partner requires specific physiological mechanism [see Reisser (1986) for a review] which can be considered, independently of morphological differences, as species characters. However, the stability of the association should be tested to exclude the possibility that a symbiosis is simulated by temporarily phagocytosed material (Reisser 1986). If, however, the algae apparently belong to the Chlorella group and have a fixed location, viz. in the ecto-endoplasmic boundary, as in most green Stentor species, the symbiosis is very likely stable. There is no reliable report in the literature that green Stentors lost their symbionts or that aposymbiotic species acquired symbionts under natural circumstances. However, under certain laboratory conditions, like prolonged cultivation in the dark or inhibition of the algae photosynthesis, aposymbiotic cells may be obtained (Schulze 1951; Tartar 1961; Reisser 1986), but all authors emphasize that Stentors are not easily divested of their symbionts and often cannot survive for longer periods without the symbionts or, at least, some algal nutrition. (ref. ID; 7228)
[Nuclear apparatus]: The shape of the macronucleus is the second main character for identifying Stentor species. Depending on species, it is vermiform (a cylindrical, irregularly curved body), nodular (a cylindrical, irregularly curved body with rather regularly spaced constrictions), moniliform (a chain of beads or nodules connected by thread-like elongations of the nuclear membrane), a single spherical mass or composed of few isolated, spherical nodules. Although there is some variability, the macronuclear shape is easily recognized if a few cells are carefully examined. Usually, several micronuclei surround the macronucleus. Their number is highly variable and has been used only once as a major species character (S. multimicronucleatus). (ref. ID; 7228)
[Cortical (pigment granules)]: The cortex of Stentor has distinct striae due to broad stripes of granules which alternate with narrow, clear furrows containing the ciliary rows. The granules have a diameter of ~0.5-1 um and are colourless or pigmented. In the latter case, the cortical striation becomes very conspicuous and mass development causes couled benthic lawns or planktonic blooms. The colour of the granules is an important character, although it varies slightly, especially in intensity, and is subject to somewhat different interpretations. Small differences (e.g. yellow, yellowish, yellow-brown) should thus not be used to separate species. The pigment is called 'stentorin' and belongs to the meso-naphthodianthrone group of compounds, which also includes the photodynamic pigments hypericin and phagopyrin (Barbier et al. 1956; Tartar 1961; Moller 1962). The function of the pigments is still under discussion. The most attractive hypothesis seems to be that the pigments mediate the orientation of the organisms in a light gradient (Moller 1962). Stentor coeruleus, a blue-pigmented species without symbiotic green algae, exhibits negative phototaxis to visible light, in addition to a step-up photophobic response (Song et al. 1980). Symbiont-bearing species show a positive phototaxis. (ref. ID; 7228)
[Shape]: The shape is highly variable due to the contractility of the body and also depends on whether the cell is attached or freely motile. In the contracted and/or motile stage, all species look very similar. In the extended form, at least two types can be distinguished: slenderly (length:width > 3:1) and broadly (length:width < / _ 2:1) trumpet shaped. A few other peculiarities occur, e.g. a bilobate peristomial bottom in S. barretti and a tail like appendage in S. caudatus, which have some value. Generally, however, the character 'shape' is of litile significant because one can hardly be sure whether a certain specimens is fully extended or not. (ref. ID; 7228)
[Size]: The size depends, like the shape, on contractility and is thus also a weak character. Usually, the highly contractile species (e.g. S. coeruleus, S. polymorphus) are longer than the less contractile ones (e.g. S. amethystinus, S tartari). Three size classes can be roughly distinguished: small (< 200 um), medium sized (200-1000 um) and large (> 1000 um). (ref. ID; 7228)
[Contractility]: Contractility is usually weaker in the smaller than in the larger species of the genus. However, it depends on various environmental factors, on the fitness of the specimen under investigation, and even on the patience of the investigator. The fully extended condition usually cannot be observed in a small drop of water under the microscope because the depth of the drop is less than the length of the cell. Generally, the optimum conditions for extension are difficult to meet. Thus, 'contractility', and the correlated characters 'shape 'and 'size', are weak and useful only for certain groups of species. (ref. ID; 7228)
[Number of somatic and peristomal: ciliary rows and adoral organelles]: The few data available indicate a high variability within and between populations. As expected, the smaller species have fewer numbers of these organelles than the larger ones. At the present state of knowledge it is, however, impossible to estimate the taxonomic value of these characters. Very likely, they overlap to a great extent. (ref. ID; 7228)
[Lorica and sensory bristles]: The presence/absence of a lorica was used by some authors as a species character. However, as with shape, size and contractility, this feature is highly ambiguous because the lack of a lorica is difficult to prove both under field conditions and in the laboratory. To mention only one example: S. multiformis was a caseless species for 150 years until Packroff and Wilbert (1991) showed that it inhabits an inconspicuous, mucilaginous lorica. The same applies for the presence/absence and arrangement of the stiff and slightly elongated sensory cilia which are difficult to recognize and have not correlate in the infraciliature (Dragesco and Dragesco-Kerneis 1986: Foissner et al. 1992). Very likely, all Stentors have sensory cilia and make a lorica under optimal conditions. (ref. ID; 7228)
[Holdfast]: The shape of the posterior holdfast organelle was used by some authors as a species character. The data obtained by Andrews (1945) and reviewed by Tartar (1961) show that the observed differences result from incomplete observations. (ref. ID; 7228)
Ecology; A detailed review of the ecology and geographic distribution of the common Stentor species, namely, S. amethystinus, S. coeruleus, S. igneus, S. muelleri, S. multiforms, S. niger, S. polymorphus and S. roeselii, has been published by Foissner et al. (1992). Here, we thus provide only a more general introduction focusing on data essential to plankton ecologists. Stentor is basically sessile via a specialized posterior holdfast granelle secreting a sticky substance (Tartar 1961). Euplanktonic species occur only rarely, if at all. However, the small species of the 'dark' group, i.e. S. amethystinus, S. fuliginosus and S. niger, tend to be planktonic and often cause heavy blooms (Stein 1867; Johnson 1893; Kasturi Bai and Narayana Murthy 1975; Bienert et al. 1991; Foissner et al. 1992). Planktonic blooms have been reported, at least once, in all common species (Foissner et al. 1992) and may comprise > 90% of the total ciliate biomass (Bienert et al. 1991). The physicochemical and biotic factors which are responsible for blooming are not known. There is some evidence that Stentor blooms can cause fish mortality (Otterstrom and Larsen 1946), problems in drinking-water reservoirs and processing, as well as in small lakes used for swimming and recreation (Foissner et al. 1992). Most Stentor species occur in normal and dystrophic freshwaters, and in slightly brackish biotopes. Usually, in marine environments Stentor is replaced by folliculinids ('bottle animals') and condylostomatids. Only S. multiformis has been recorded from marine, freshwater and even terrestrial biotopes (Stein 1867; Penard 1922; Stout 1961; Foissner et al. 1992). However, it is uncertain whether all populations are conspecific. Resting cysts are known from a few species. Data on geographical distributions are uncertain because identifications are often questionable. Some species are very likely cosmopolits (e.g. S. igneus, S. multiformis, S. coeruleus, S. polymorphus, S. roeselii), others are possibly restricted to Gondwanian areas (e.g. S. araucanus, S. multimicronucleatus); S. baicalius is possibly endemic to Lake Baikal. Some Stentor species are fairly good indicators of organic population in running waters and can survive anaerobic conditions for up to 12 h. In activated sludge, Stentors usually indicate good operating conditions (Foissner et al. 1992). Stentor is polyphagous, i.e. it feeds on various heterotrophic (e.g. ciliates and flagellates) and autotrophic (e.g. diatoms) protists. Even small metazoans like rotifers and oligochaetes are attacked, and cannibalism has been observed (Gelei 1925; Grula and Bovee 1977). Detailed autecological data are available mainly from S. coeruleus (Rapport et el. 1972; Wenzel and Liebsch 1975; Laybourn 1976). These studies show that Stentor is a very efficient filter feeder and energy converter, which is reasonable considering its large oral apparatus. (ref. ID; 7228)
Nomenclature; Stentor is a nomen conservandum (Hemming 1954; Kirby 1954). (ref. ID; 7228)
Type species; Stentor muelleri Ehrenberg, 1831 (ref. ID; 7228)

Stentor acrobaticus Silen, 1948 (ref. ID; 7228)
Notes; A peculiar marine species which certainly does not belong to the genus Stentor. It possibly secretes a rather compact rod on which is glides up and down rapidly. Found only once in small numbers on a Fuscus leaf on the west coast of Sweden. (ref. ID; 7228)
Stentor albus Fromentel, 1876 (ref. ID; 7228)
Notes; The figures clearly show freshwater tintinnids which left their lorica. Fromental even mentions that the contractile vacuole moves up and down with the peristomial bottom, which is typical for tintinnids. A more accurate identification is, however, impossible. We thus suggest considering S. albus as a species indeterminata. (ref. ID; 7228)
Stentor amethystinus Leidy, 1880 (ref. ID; 1621, 1629, 4610, 4613, 7228) 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)
Notes; A detailed description and discussion of synonymy, morphology, and ecology can be found in Foissner et al. (1992). This violet to purple-red-pigmented, symbiotic algae-bearing freshwater species has been thoroughly redescribed by Dragesco (1970), Foissner (1980), Foissner et al. (1992) and Nilsson (1986). Stentor amethystinus has ~90-120 somatic kineties, 20-25 peristomial kineties and 200-300 adoral membranelles (Foissner et al., 1992). It is probably often misidentified as S. niger which, however, lacks symbiotic algae and has brownish pigment granules. Easily confused with S. fuliginosus which differs from S. amethystinus by the colour of the cortical granules and the lack of pigment granules around the micronuclei. (ref. ID; 7228)
Measurements; 300-600 um long. (ref. ID; 1618)
Stentor anceps Fromentel, 1876 (ref. ID; 7228)
Notes; This ~90 um long, cylindroid, colourless organism is very likely a telotroch stage of a peritrichous ciliate, as also discussed by Fromentel. The description is very incomplete and we thus suggest considering S. anceps as a species indeterminata. (ref. ID; 7228)
Stentor andreseni Nilsson, 1986 (ref. ID; 7228)
Notes; This binucleate, African freshwater species was thoroughly described and a possible synonymy with S. tartari was also considered. However, Nilsson (1986) decided against synonymy because she assumed that S. tartari 'should be a slender ciliate having about half the number of ciliary rows found in S. andreseni'. However, this is a weak character, especially considering the identical live size (~ 300 um) in both species, which suggests that their ciliary row number is similar and was underestimated by Narayana Murthy and Kasturi Bai (1974) in S. tartari. We thus synonymize S. andreseni with S. tartari. The binucleate, purple-red S. amethystinus found by Vuxanovici (1961) in Lake Herastrau, near Bucharest, very likely also belongs to this species. Stentor igneus sensu Johnson (1893), found in two ponds in North America, is also S. tartari, as indicated by the characters given (reddish, two, rarely one, three, four, five or six macronuclear segments, symbiotic algae, rather broadly trumpet shaped). (ref. ID; 7228)
Stentor araucanus Foissner & Wolel, 1994 (ref. ID; 4613, 7228 original paper)
Diagnosis; Size in vivo 100-270 x 80-200 um, broadly vase to trumpet shaped. Macronucleus vermiform to slightly nodular. Cytoplasm with symbiotic green algae. Cortical granules blue-green. Sixty-six somatic kineties, 10 peristomial ciliary rows and ~150 adoral membranelles on average. (ref. ID; 7228)
Description; Freely motile specimens usually ~230 x 130 um in size, starving cells become considerably smaller, ~100-150 x 80 um. Only slightly contractile. Motile stage vase shaped to broadly turbinate, asymmetrical because flattened ventrally and bulging dorsally. Macronucleus vermiform to slightly nodular, usually in middle third of cell, 10-15 um in diameter, shape highly vaiable, often horseshoe like, not covered by pigment granules. Up to 24 micronuclei with a diameter of 1.8-2.5 um surround macronucleus. Contractile vacuole as in other members of genus. Cortical granules intensively blue-green, very similar to those of S. coeruleus, in vivo 0.8-1.2 um in diameter, in formalin-fixed material 1-1.5 um, arranged in distinct stripes between somatic kineties. Cells appear as dark spots to the naked eye and blueish green in the dissecting microscope. Cytoplasm of all specimens and populations examined with symbiotic algae of the Chlorella type, i.e. having a green, cup-shaped chloroplast and producing four offspring during division. Symbionts spherical to slightly ellipsoid, 3-8 um (usually 4-6 um) in diameter, size and number (580-2300 per ciliate) depending on season. In nature probably feeding on various algae; in the laboratory, ingestion long bacterial rods was observed. Swims rather slowly, ~2-3 times its length per second, by clockwise rotation (if viewed from anterior pole) about its longitudinal axis. Never attached to walls and natural sediment (vulcanic grains) in aquaria. Thus, S. araucanus is probably euplanktic; it has, however, a patch of disordered basal bodies at its posterior end, indicating the presence of a holdfast organelle. Somatic and oral infraciliature as in other small members of the genus, e.g. S. amethystinus (Foissner et al. 1992) and S. fuliginosus (Dragesco 1966). (ref. ID; 7228)
Etymology; 'Araucanus' refers to the native inhabitants of South Chile. Araucania is also province in Chile and the name of a genus of lofty coniferous trees native the southern hemisphere. (ref. ID; 7228)
Type location; Plankton of Lake Pirehueico, South Chile, 71 degrees 48'W, 39 degrees 56'S. (ref. ID; 7228)
Type specimens; Not available because silver impregnation was too mediocre for preparing permanent slides. (ref. ID; 7228)
Stentor attenuatus Maskell, 1887 (ref. ID; 7228)
Notes; We agree with Kahl (1932) that this species is a junior synonym of S. coeruleus from which it supposedly differs by 'the remarkable slenderness and great length of the stem', a really insufficient character. (ref. ID; 7228)
Stentor auricula Kent, 1881 (ref. ID; 1621, 7228)
Notes; Very likely a Condylostoma or Folliculina. We thus exclude it from Stentor. The species name is considered as a noun in apposition. (ref. ID; 7228)
Stentor auriculatus Kahl, 1932 (ref. ID; 1335, 7228)
Syn; Stentor auricula Gruber, 1884 (ref. ID; 1335)
Notes; This marine species was described by Kahl after observations from Daday (1886) and Gruber (1884), who identified their populations as S. auricula Kent. Faure-Fremiet (1936) reinvestigated S. auriculatus and showed that it belongs to Condylostoma. Later Andrews (1948) suggested that Kent (1881) overlooked the beaded macronucleus, i.e. synonymy of S. auricula Kent and S. auriculatus Kahl. More recently, Jankowski (1978), without new evidence, constructed the new genus Condylostentor for S. auriculatus Kahl. Later, Jankowski (1980) even proposed a new family, Condylostentoridae, for this species-again without new data. (ref. ID; 7228)
Stentor baicalius nom. nov. (pro S. pygmaeus Swarczewsky, 1929 preoccupied by S. pygmaeus Ehrenberg, 1831, now in the genus Colacium, Euglenophyta) (ref. ID; 7228)
Notes; This species, which is attached to crustaceans of Lake Baikal, was originally described from formalin-fixed material only. It has been rediscovered by Gajewskaja (1933) who, however, synonymized it with S. multiformis. In our opinion, S. baicalius is well characterized by its sea green cortical granules, 4-6 macronuclear beads and the club-like body shape. (ref. ID; 7228)
Stentor barretti Barrett, 1870 (ref. ID; 4689 redescribed paper, 7228) 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)
This colourless freshwater species is well defined by its bilobate peristomial bottom, its nodular macronucleus and a thread-like caudal elongation used to anchor the organism at the substrate (Warren 1985). (ref. ID; 7228)
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 castaneus Wright, 1859 (ref. ID; 7228)
Notes; This species, which was found in a freshwater pond of the Edinburgh Botanical Gardens, is very superficially described ('a small species of Stentor of a deep chestnut colour which is in the habit of secreting a lorica like that of S. mulleri'). We thus follow Stein (1867) in synonymizing it with S. niger. (ref. ID; 7228)
Stentor caudatus Dragesco, 1970 (ref. ID; 7228)
Notes; This is an African freshwater species which was, however, observed only in an old culture of Frontonia vesiculosa. It is rather vaguely separated from S. muelleri (shape, absence of lorica and sensory bristles, vacuolated and fibrous cytoplasm, but has a distinctly higher number of macronuclear segments (30-42). We thus keep it separate. This species needs redescription. (ref. ID; 7228)
Stentor coeruleus Ehrenberg, 1830 (ref. ID; 1621, 1629, 2245, 3116, 4070) reported year? (ref. ID; 1219, 1618, 3342, 3343, 4056, 7623, 7624, 7677) or (Pallas, 1766) Ehrenberg (1831) (ref. ID; 4488, 4610, 7228) reported author and year? (ref. ID; 191, 3292, 4550, 4675, 5969, 7541, 7681, 7742)
Syn; Brachionus stentoreus var. coerulei Pallas, 1766 (ref. ID; 4610, 7228); 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)
Regeneration of the oral apparatus. (ref. ID; 7681)
Ultrastructural observations on the buccal apparatus. (ref. ID; 7742)
Notes; This large, blueish freshwater species has a moniliform macronucleus and is one of the favourites of the protozoologists. Many basic studies on the physiology and regeneration of ciliates were carried out with S. coerules and excellently reviewed by Tartar (1961). The morphological and ecological data were summarized by Foissner et al. (1992). The species has three synonyms: S. attenuatus, S. sphaericus, S. striatus. Fernandez-Leborans and Zaldumbide (1983) reported symbiotic algae in this species. The algae are of the Chlorella type, but unusually large: 15 x 12 um. Unfortunately, no details are provided for the ciliate, whose status thus cannot be evaluated. (ref. ID; 7228)
Measurements; Length 1-2 mm (fully extended). (ref. ID; 1219, 1618, 3343)
270-700 um. (ref. ID; 3342)
Stentor conicum Vuxanovici, 1962 (ref. ID; 7228)
Notes; Described from a single, 1400 um long specimen found in Lake Fundeni near Bucharest. We synonymize it with S. elegans. (ref. ID; 7228)
Stentor deformis Fromentel, 1867 (ref. ID; 7228)
Notes; This triangular, brown-yellow species is apparently acontractile, and has one contractile vacuole each in the anterior and posterior third. Size and nuclear apparatus are not indicated. The acontractility indicates that it belongs to another genus; very likely it is a morbid Frontonia, possibly F. elliptica, as indicated by the two contractile vacuoles. We suggest considering S. deformis as a species indeterminata. (ref. ID; 7228)
Stentor elegans Fromentel, 1867 (ref. ID; 7228)
Notes; This colourless ('le tegument est blanc, transparent') freshwater species which is, like most of Fromentel's Stentor species, not mentioned in Kahl's revision, has an ellipsoid macronucleus. Although differing in some details S. conicum and S. pallidus have the same main characteristics (cortical granules colourless, single macronuclear bead, no symbiotic algae) and must thus be synonymized with S. elegans. It is a rare species, all authors observed only one or a few specimens. We recently found a single specimen in a clean brook near Salzburg, Austria. (ref. ID; 7228)
Stentor elongatus Minkewitsch, 1898 (ref. ID; 7228)
Notes; This is apparently a long and slender freshwater species with a roundish macronucleus. Other details are not mentioned. We thus suggest considering S. elongatus as a species indeterminata. (ref. ID; 7228)
Stentor felici Villeneuve- Brachon, 1940 (ref. ID; 7228) reported year? (ref. ID; 1335)
Notes; The founder of this taxon did not compare it with species previously described. The most distinctive character mentioned is the yellow colour, all other details match small individuals of S. muelleri. However, Villeneuve-Brachon (1940) did not specify a reason for the color. In our experience, all medium-sized and large, unpigmented Stentors look more or less yellowish or brownish simply because of their thickness. We thus synonymize S. felici with S. muelleri. (ref. ID; 7228)
Stentor fimbriatus Fromentel, 1867 (ref. ID; 7228)
Notes; This 100 um long freshwater species has, like dividing or regenerating Stentors, a lateral, lobed protuberance and, occasionally, a second contractile vacuole near the posterior end. Fromentel (1876) saw several such specimens, but does not mention whether in one or several populations. The nucleus is vermiform, the color is not indicated. In our opinion, this species is a regenerating fragment of S. roeselii. (ref. ID; 7228)
Stentor fuliginosus Forbes, 1891 (ref. ID; 7228)
Basionym; Stentor igneus var. fuliginosus (ref. ID; 7228)
Notes; We raise this freshwater variety to species level and rediagnose it as follows: slenderly trumpet shaped and 200-300 um long when fully extended. Usually one macronuclear bead and several micronuclei. Appears black or black-brown at low magnification due to symbiotic green algae and brownish, yellow-brown or red-orange-coloured cortical and cytoplasmic granules. This diagnosis is based on the poor original description (without figure; size and macronucleus not indicated; pigment granules not described in detail) and on the description of S. igneus var. nigricans Johnson, 1893, as well as on the much more detailed data of Dragesco (1966) and Kawakami (1984), who identified their populations with S. niger which, however, lacks symbiotic algae. Dragesco (1966) studied 1068 specimens and found that 959 had one macronuclear bead, 82 two, 22 three, 3 four and 2 even five pieces. Stentor fuliginosus has, according to Dragesco (1966), 64-72 somatic kineties, 24 peristomial ciliary rows and ~140 adoral membranelles. However, a reivestigation of the original slides. which were kindly supplied by Prof. Dragesco, showed that he greatly underestimated these character. Thus, the morphometric characteristics of S. fuliginosus are very similar to those of S. amethystinus. Synonymy with that species cannot be excluded, although the cortical granules have a slightly different colour and the micronuclei of S. fulginosus are never surrounded by pigment granules (Dragesco, 1966, and personal communication), which is corroborated by a micrograph in Kawakami's paper. (ref. ID; 7228)
Stentor fuscus Fromentel, 1867 (ref. ID; 7228)
Notes; All characters mentioned match S. roeselii. (ref. ID; 7228)
Stentor gallinulus Penard, 1922 (ref. ID; 7228)
Notes; Name suggested by Penard (1922) for the freshwater form of S. multiformis if futher research proves that it is different from the marine variety. (ref. ID; 7228)
Stentor globator Stokes, 1885 (ref. ID; 1621, 7228)
Notes; A small (85 um), spherical freshwater organism with two contractile vacuoles at the posterior end where a tail-like prolongation used to anchor the cell at the substrate temporarily appears. No data are available on the nuclear apparatus, the color and the number of specimens observed. We agree with Kahl (1932) that this is a doubtful species, very likely a regenerating Stentor fragment. In the absence of newer records, we suggest considering S. globator as a species indeterminata. (ref. ID; 7228)
Stentor igneus Ehrenberg, 1838 (ref. ID; 1308, 1621, 1629, 2245, 4488, 4610, 4730, 7228) reported year? (ref. ID; 1618, 3698)
Description; Rose-colored or colorless; macronucleus oval; ciliation uniform. (ref. ID; 1618)
Notes; This small, reddish-pigmented freshwater species is well defined due to the redescriptions by Foissner (1980) and Song and Wilbert (1989). Foissner et al. (1992) reviewed the data available on its morphology and ecology. Stentor igneus lacks symbiotic algae and has two synonyms: S. roseus and S. ruber. For nomenclature, see Foissner (1987). Schulze (1951) mentions a S. igneus with symbiotic green algae. Unfortunately, the taxonomic status of this population remains obscure since no morphological data on the ciliate were provided. (ref. ID; 7228)
Measurements; 200-400 um long. (ref. ID; 1618)
Stentor introversus Tartar, 1958 (ref. ID; 1618, 4610, 7228)
Description; Adoral zone retractable; blue-green; with 70-90 ectoplasmic stripes of blue-green granules; macronucleus moniliform; fresh water. (ref. ID; 1618)
Notes; This species matches most characters of S. coeruleus. It is, however, smaller [450 um, up to 580 um, according to Jones (1974); weak character] and the entire zone of adoral membranelles cannot only contract, but also retract. We recognize this form as a distinct species because heteroplastic graft combinations between S. introversus and S. coeruleus did not survive (Tartar, 1958), and because Tartar was an expert on S. coeruleus, making it unlikely that he was mistaken. (ref. ID; 7228)
Measurements; 103-306 (up to 450) by 135-288 um. (ref. ID; 1618)
Stentor katashimai Kumazawa, 1973 (ref. ID; 7228)
Notes; This species has the main characteristics of S. muelleri, from which it is said to differ by the lack of a lorica, a more stocky shape and the possession of a buccal pouch (Kumazawa 1974). These characters are clearly insufficient and S. katashimai is thus synonymized with S. muelleri. (ref. ID; 7228)
Stentor loricaus nom. corr. Bary, 1950 (ref. ID; 7228)
Basionym; Stentor loricata (ref. ID; 7228)
Notes; This is a well-defined, medium-sized Stentor found attached to leaves and twigs in a small stream of New Zealand. Its dark green pigment granules are odd, but occur also in some hypotrich ciliates (Berger and Foissner, 1989). (ref. ID; 7228)
Stentor magnus Kumazawa, 1973 (ref. ID; 7228)
Notes; This species has the main characteristics of S. roeselii, from which it is said to differ by the lack of a lorica and in body shape and proportions, as well as in the arrangement of the sensory bristles (Kumazawa, 1974). These characters are clearly insufficient and S. magnus is thus synonymized with S. roeselii. (ref. ID; 7228)
Stentor muelleri Ehrenberg, 1831 (ref. ID; 4610, 7228)
Junior synonyms; Stentor felici Villeneuve-Brachon, 1940 (ref. ID; 7228); Stentor katashimai Kumazawa, 1973 (ref. ID; 7228)
Notes; A detailed description and discussion of synonymy, morphology and ecology can be found in Foissner et al. (1992). This freshwater species is well defined by its moniliform macronucleus and the absence of pigmented cortical granules. It has ~30-50 somatic kinetics and ~10 peristomial ciliary rows. (ref. ID; 7228)
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, 7228) or (O.F. Muller, 1786) Stein (ref. ID; 1621, 1629)
Syn; Vorticella multiformis O.F. Muller, 1786 (ref. ID; 4610) reported author and year? (ref. ID; 7228)
Description; Dark blue to bluish green; anterior end not expanded; macronucleus oval. (ref. ID; 1618)
Notes; A detailed description and discussion of synonymy, morphology and ecology can be found in Foissner et al. (1992). This is a small, blueish species occurring in marine, freshwater and terrestrial biotopes. It is, however, still uncertain whether the marine and freshwater populations are truly conspecific. In the absence of detailed evidence, we follow Stein (1867) and Kahl (1932), who assume conspecificty. This species is sparingly mentioned in faunal lists, although it is rather frequent (Schuberg 1896; Foissner et al. 1992); possibly it has often been mistaken for small individuals of S. coeruleus, Stentor multiformis has 34-45 somatic kineties, 6-9 peristomial ciliary rows and 100-150 adoral membranelles (Packroff and Wilbert 1991). Two junior synonyms are known: S. gallinulus and S. nanus. (ref. ID; 7228)
Measurements; 150-200 um long. (ref. ID; 1618)
Stentor multimicronucleatus Dragesco, 1970 (ref. ID; 7228)
Notes; This medium-sized, African freshwater species is well characterized by its 52-142 micronuclei which surround a conspicuously large macronuclear mass. (ref. ID; 7228)
Stentor nanus Fromentel, 1876 (ref. ID; 7228)
Notes; The blueish color, the ellipsoid macronucleus and the small size (50 um) clearly indicate synonymy with S. multiformis, as also suggested by Penard (1922). (ref. ID; 7228)
Stentor niger (O.F. Muller) (ref. ID; 1618), (O.F. Muller, 1773) Ehrenberg, 1831 (ref. ID; 4610, 7228) 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) reported author and year? (ref. ID; 7228)
Description; Yellowish or brown; macronucleus oval. (ref. ID; 1618)
Notes; A detailed description and discussion of synonymy, morphology and ecology can be found in Foissner et al. (1992). This medium-sized, mononucleate freshwater Stentor differs from S. amethystinus and S. fuliginosus, with which it has probably often been confused, mainly by the lack of symbiotic algae. This has been independently observed by Stein (1867) and Kahl (1932), and must thus be acknowledged as a main species character and difference from S. amethystinus and S. fuliginosus. Stentor niger has two junior synonyms: S. castaneus and S. pediculatus. Stentor niger sensu Dragesco (1966, 1970) and sensu Kawakami (1984) belong to S. fuliginosus. (ref. ID; 7228)
Measurements; 200-300 um long. (ref. ID; 1618)
Stentor oligonucleatus Sokoloff, 1930 (ref. ID; 7228)
Notes; This species, which Sokoloff (1930) first considered as a variety of S. viridis, very much resembles S. tartari in size, shape and nuclear apparatus, and is thus not a junior synonym of S. polymorphus, as suggested by Kahl (1932). It differs from S. tartari, S. amethystinus, S. fuliginosus and S. nigra by its colourless cortical granules. This, however, suggests synonymy with S. pyriformis, a species not mentioned in Kahl's revision. Nomenclature: described as species nova also by Samano and Sokoloff (1931). (ref. ID; 7228)
Stentor pediculatus Fromentel, 1876 (ref. ID; 7228)
Notes; This small (250 um), mononucleate, brown freshwater species is characterized by minute, V-shaped processes with which it attaches to the substrate. Such processes also occur in other species [e.g. S. polymorphus, Figure 16 in Foissner et al. (1992)] and are indeed a genus character (Andrews 1945; Tartar 1961). We thus agree with Kahl (1932), who synonymizes S. pediculatus with S. niger. (ref. ID; 7228)
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, 7228), (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) reported author and year? (ref. ID; 7228)
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)
Notes; A detailed description and discussion of morphology and ecology can be found in Foissner et al. (1992). Stentor polymorphus is well defined by its symbiotic algae and colourless cortical granules; it has no junior synonyms. (ref. ID; 7228)
Measurements; Length 1-2 mm (fully extended). (ref. ID; 1219, 1618)
Stentor pyriformis Johnson, 1893 (ref. ID; 7228) reported year? (ref. ID; 1618)
Notes; This is a well-defined species overlooked by Kahl (1932). It even has a junior synonym: S. oligonucleatus. (ref. ID; 7228)
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, 7228) 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)
Notes; A detailed description and discussion of synonymy, morphology and ecology can be found in Foissner et al. (1992). This colourless and common freshwater species is highly variable (Dragesco 1970) and thus has many synonyms: S. fimbriatus, S. fuscus, S. gracilis, S. magnus, S. roeseli f. stagnalis, S. viridis. Stentor roeselii has ~40-80 somatic kineties, 14-42 peristomial ciliary rows and > 150 adoral membranelles. (ref. ID; 7228)
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)
Stentor roeseli f. stagnalis Jirovec et al., 1953 (ref. ID; 7228) reported author and year? (ref. ID; 4610)
Notes; This variety differs from the type by its paint brush-shaped holdfast, used to anchor it in the mud of polluted rivers. In our opinion, this character is insufficient to establish new species or varieties (cp. S. pediculatus). (ref. ID; 7228)
Stentor roseus Fromentel, 1876 (ref. ID; 7228)
Notes; All characters mentioned match S. igneus. (ref. ID; 7228)
Stentor ruber nom. corr. Bary, 1950 (ref. ID; 7228)
Basionym; Stentor rubra (ref. ID; 7228)
Notes; Bary distinguished this species from S. igneus by small shape differences, which we consider insufficient. (ref. ID; 7228)
Stentor sphaericus Vuxanovici, 1961 (ref. ID; 7228)
Notes; This poorly described species is very likely based on morbid specimens of S. coeruleus which occurred at the same site (Lake Fundeni, near Bucharest). This is also indicated by its small size (80-250 um), the globular shape and moniliform macronucleus. The colour of the cortical granules is not mentioned: cytoplasm is said to be green-grey. (ref. ID; 7228)
Stentor striatus Barraud-Maskell, 1886 (ref. ID; 1621) or Maskell, 1886 (ref. ID; 7228)
Notes; We agree with Kahl (1932) that this freshwater species is a junior synonym of S. coeruleus. Maskell (1886) did not compare his new species with those described earlier. Kahl (1932) cites this species as 'S. striatus Barraud-Maskell, 1886'. However, Barraud only collected the species and is not the author of the paper. (ref. ID; 7228)
Stentor tartari Narayana Murthy & Kasturi Bai, 1974 (ref. ID; 7228)
Notes; This freshwater species from Bangalore (India) is well defined by its two macronuclear beads, the reddish colour and the symbitoic green algae. It has two synonyms: S. andreseni and S. igneus sensu Johnson (1893). (ref. ID; 7228)
Stentor viridis Ghosh, 1921 (ref. ID; 7228)
Notes; We agree with Kahl (1932) that this yellowish freshwater species from Calcutta is a junior synonym of S. roeselii. The characteristics mentioned Ghosh (1921) are insufficient, namely size, lack of sensory bristles and lorica (cp. S. magnus), and yellow colour (cp. S. felici). (ref. ID; 7228)