Tetrahymena Furgason, 1940 (ref. ID; 2014, 7704)
Class Oligohymenophora: Subclass Hymenostomata: Order Hymenostomatida (ref. ID; 2014)
Oligohymenophora (ref. ID; 7267)

[ref. ID; 2014]
Small to medium ciliate, ovoid to pyriform with anterior end narrowed. Oral aperture small in anterior body third, pyriform in outline with its axis parallel to that of the major body axis. There is an undulating membrane on the right and 3 small inconspicuous membranelles on the buccal cavity leads to the splitting of these membranelles such that 5 or 6 membranelles may be found; similar splitting of the membranelles has been noted in some microstomes (Kaczanowski 1975). Macrostome formation allows the cell to lead a carnivorous way of life. Somatic ciliation complete with a straight pre-oral suture. Some rarely with a caudal cilium. Single terminal contractile vacuole. Macronucleus spherical centrally positioned. Elliott (1973). A recent paper by Nanny and McCoy (1976) has divided organisms previously known as Tetrahymena pyriformis into 14 species.
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; 7115]
In general, the use of morphological characters revealed by silver staining remains the primary way of differentiatng between species of Tetrahymena that are morphologically distinct (Corliss 1973). However many, perhaps most, Tetrahymena species are not easily identified via microscopy either because they exhibit polymorphic life cycles, or because they are cryptic or sibling species (Chantangsi et al. 2007; Corliss 1973; Simon et al. 2008). For this reason, a genetic approach to species identification has been very effective. Although a large number of environmental isolates are often asexual or sexually immature, mating compatibilities can be used to discriminate many species of Tetrahymena (Doerder et al. 1995; Elliott & Gruchy 1952; Nannery et al. 1998). However, this technique requires living stocks of multiple mating types, making mating reactions impractical for routine species identification (Sonneborn 1959). Early efforts at molecular identification of species without the use of living strains made use of differences in isozyme mobilities, and while this method resolved some species, it failed to resolve others (Chantangsi et al. 2007; Nanney et al. 1980; Tail 1978). DNA-based molecular approaches have been used to successfuly elucidate phylogenetic relationships in the genus Tetrahymena as early as 1990 (Brunk et al. 1990). Jerome and Lynn (1996) used small subunit (SSU) rRNA, internal transcribed spacer (ITS) regions, and a portion of the large subunit (LSU) rRNA gene sequences to identify cryptic species within the Tetrahymena pyriformis species complex. However, they found that interspecific variation is very low in these genes and concluded that a faster-evolving and thus more variable marker would be a better tool for sequence-based species identifications. Since the mitochondrial genome is widely known to evolve faster than the nuclear genome (Brown et al. 1979; Mclntosh et al. 1998), Hebert et al. (2003) proposed using a 650 base-pair region of the cytochrome c oxidase subunit (cox-1) gene as the universal barcode sequence in animals to enable identification of species. Lynn and Struder-Kypke (2006) used variation in cox-1 to demonstrate that Tetrahymena species with identical SSUrRNA gene sequences were divergent, and that intraspecific divergence for cox-1 sequences was less than 1% in 14 isolates of Tetrahymena thermophila. In a more extensive study, Chantangsi et al. (2007) analyzed cox-1 sequences from 75 isolates representing 36 Tetrahymena species. They found that < 1% intraspecific sequence divergence values also characterized strains of Tetrahymena borealis, Tetrahymena lwoffi, and Tetrahymena patula, and confirmed that threshold value using additional strains of T. thermophila. These results suggest that an empirically-derived threshold of < 1% might be used to discriminate known species, especially since the average differences among species was about 10%. (ref. ID; 7115)

[ref. ID; 7267]
The hymenostome ciliate genus Tetrahymena comprises at least 33 species. Although most species in the genus are free-living, infections of various invertebrates (ranging from gastropods to insects) by tetrahymenine ciliates have been reported frequently in the literature. These parasitic tetrahymenine ciliates include Lambornella clarki (Corliss and Coats 1976), Lambornella stegomyiae (Keilin 1921; Corliss and Coats 1976), Tetrahymena limacis (Warren 1932; Kozloff 1946), Tetrahymena corlissi (Thompson 1955), Tetrahymena rostrata (Kahl 1926; Corliss 1952), Tetrahymena rotunda (Lynn et al. 1981), Tetrahymena chironomi (Corliss 1960), Tetrahymena dimorpha (Batson 1983), and Tetrahymena sialidos (Baston 1985). Of the parasitic Tetrahymena species listed above, the last four are well-documented faculative parasites in insects. (ref. ID; 7267)

[ref. ID; 7435]
The molecular diversity within the D2 domain of the 23S ribosomal RNA molecules of "tetrahymenids". (ref. ID; 7435)

[ref. ID; 7704]
Although the generic name Tetrahymena of only 43 years old (Furgason 1940), its type-species, T. pyriformis, under other names, has been known for at least 200 years: in fact, like Paramecium, it was very likely one of the ciliates observed by A. van Leeuwenhoek in the 17th century (Corliss 1975). Still, the immense popularity of Tetrahymena species has dated principally from the early 1950's, stimulated by the great ease with which some of them can be cultured under axenic (even chemically defined) conditions in the laboratory coupled with their genetic manipulability. A vast amount of literature has been generated by studies of Tetrahymena in diverse fields. The bulk of the papers on the biochemistry and physiology of these ciliates were/are concerned with several amicronucleate (asexual) strains (see Corliss 1973; Elliott 1973; Hill 1972). Naturally, genetic studies have been carried out only with sexual strains (see Nanney 1980; Sonneborn 1974). Tetrahymena as considered smaller than Paramecium; but its key morphological features can also be recognized by light microscopy, and its several major species are distinguishable from each other and from species of such neighboring hymenostome genera as Glaucoma and Colpidium (Corliss 1953, 1971, 1973, 1979; Czapik 1968; Dragesco 1970; Jankowski 1967), the older literature notwithstanding. Some 30 years ago, with Sonneborn's classical investigation on sexuality of Paramecium as a model (Nanney, Elliot, and colleagues (Elliott and Gruchy 1952; Elliott and Hayes 1953; Elliott and Nanney 1952; Nanney and Caughey 1953) discovered conjugation and described mating types in what they called Tetrahymena pyriformis (in the same year, Corliss 1952, reported autogamy in T. rostrata; of course, Maupas 1889, had observed conjugation in T. patula more than half a century earlier). Before long, a system similar to that used for Paramecium was established: the terms varieties and ultimately syngens (Elliott 1970; Gruchy 1955; Nanney 1968; Sonneborn 1957) appeared in the literature on Tetrahymena. Once again, it became increasingly clear that "sibling species" deserved separate taxonomic designations; however, the story here was/is somewhat more complicated than in the case of Paramecium. Neverthelss Nanney, appropriately, accepted the responsibility for taking the final formal step: in 1976, with McCoy (Nanney and McCoy 1976), he published a "characterization of the species of the Tetrahymena pyriformis complex". This occurred in the year following appearance of Sonneborn's (1975) action of "P. aurelia". (ref. ID; 7704)
[Taxonomic-nomenclatural consequences]: Again, as in the case of the aurelia complex, the steps taken by Nanney and co-workers were laudable. The taxonomic situation here, however was not as directly solvable as with Paramecium. As a result, many biologists, even numerous ("non-genetical") tetrahymenologists, whose interests in these small hymenostome ciliates represent a diversity of fields, are apparently (still) confused. It was not possible to name all involved species after numbered sygens in the Tetrahymena pyriformis case. There was either inadequate information to assign a species designation to each syngen or, as in the case of syngen 6 and 8, it was dicovered that the members of separate syngenic groups could interbreed with production of viable clones of progeny. (This would cause gaps in the latinized numbering system). Slefing strains have caused additional confusion. Furthermore the long-known strains of amicronucleate tetrahymenas (often with mixed-up strain designations) have added a confounding parameter that did not exist in the case of the old "Paramecium aurelia". Finally, in the present case, the name Tetrahymena pyriformis itself has been preserved, appropriately assigned to one of the classical asexual strains or phenosets. (ref. ID; 7704)
Names of the species involved. Currently, there are 17 species comprising the entire Tetrahymena pyriformis complex (shortenable to the "pyriformis complex" when it clear that these Tetrahymena are the topic). Unlike the situation for the P. aurelia complex, the recognition of possibly many more may be predicted. Of the 17 described to date, four embrace solely asexual (amicronucleate) strains: 10 are the sexual "sibling" species recognized by Nanney and McCoy; and three are additional "genetic" species recently named by Nyberg (1981). (ref. ID; 7704)
The amicronucleate problem. For many years, all members of "Tetrahymena pyriformis" (often popularly but incorrectly known as "Glaucoma pyriformis" or "Tetrahymena geleii") established in laboratory culture turned out to be strains without a macronucleus. Because of the ease with which these ciliates were culturable axenically, they early became ideal in physiological and biochemical researches of a great variety of kinds, thus rapidly surprassing Paramecium and all others as the most popular protozoa in such work. Strain designations had often been assigned to various populations isolated in one laboratory or another; it thus came as a shock to learn, in recent years, that many "pure" lines had/have become mixed contaminated, or mislabeled with free exchange and transfer between workers over thousands of tetrahymena generations. This was verified when comparison by electrophoretic mobilities, or use of other biochemical properties, was made using subcultures of cultures obtained from different laboratories, cultures that bore the same designations but turned out to be quite different? On occasion, worse still, cultures that carried entirely different labels were shown to be the same strain. Such corrective investigations have resulted in recognition of five phenotypic sets (phenosets), replacing the now unreliable clusters of old strain designations, of "amic" tetrahymenas (Bordern et al. 1973; McCoy 1975; Nielsen and Andronis 1975). Four of these "amic" phenosets, viz., A, B, C, and E, were recognized as separate species by Nanney and McCoy (1976). The name Tetrahymena pyriformis (Ehrenberg, 1830) Lwoff, 1947 - see discussion of its complicated nomenclatural history in Corliss (1953) and Corliss and Dougherty (1967) - was arbitrarily retained to include especially the celebrated "GL" strains of Andre Lwoff, isolated and established in axenic culture in 1922 and maintained in various laboratories ever since; it is a member of the phenoset called "A" by Borden et al. (1973). The strain "E" used by Corliss (1971) in his deposition in the U.S. National Museum of neotype material for T. pyriformis is also in phenoset A, so no provision of the International Code of Zoological Nomenclature has been broken. T. pyriformis remains the type-species of the genus Tetrahymena Furgason, 1940. But notice that, since 1976, this species can no longer be identified simply by possession of the morphological characteristics that, in the main, are also found in many other members of the entire pyriformis complex: it must also show the properties that separate phenoset A from four other phenosets and from some 15 micronucleated syngens. The three other species of "amics", the ones named as new by Nanney and McCoy (1976), are : T. elliotti (= phenoset B); T. furgasoni (= phenoset C); and T. lwoffi (= phenoset E). Since nothing can be known about restricted or unrestricted gene flow in populations that cannot breed, Nanney (in Nanney and McCoy 1976) has defined an asexual species as "a population with approximately the same amount of molecular (genetic) heterogeneity as a sexual species" and one that is "discontinuous in that heterogeneity from other sexual and asexual species". (ref. ID; 7704)
The "genetic" species. The 10 sibling species recognized and formally named by Nanney and McCoy (1976), from among the dozen syngens known at that time, are as follows: T. americanis, T. australis, T. borealis, T. canadensis, T. capricornis, T. cosmopolitanis, T. hyperangularis, T. pigmentosa, T. thermophila, T. tropicalis. The most extensively studied species in genetic research to date has been T. thermophila, under its former designation of variety or syngen 1 of "T. pyriformis" sensu lato (Sonneborn 1974). Its newer name is based on its tolerance for high temperatures (e.g., up to 41 degrees C). The specific names of the other species reflect either some unusual character or the geographical area in which the organisms have been found. Tetrahymena americanis is the most commonly collected species in North America, and to date it has never been found elsewhere in the world. Recently, Nyberg (1981) has described what he considers to be three additonal"biological" species assignable to the pyriformis complex. Two were new mating groups collected from the wild that would have been syngens 13 and 14 if that had been the only system in vogue in 1981. The other was old syngen 5, found by Nyberg in natural populations, which Nanney and McCoy (1976) had cautiously declined to name as new. These three most recent pyriformis complex species, formally named by Nyberg in his 1981 paper, are: T. hegewischi, T. nipissingi, and T. sonneborni. (ref. ID; 7704)
[Characteristics used to separate species]: The widespread existence of amicronucleate ("genetically dead") strains, not to mention selfers, has confounded the problem. Enzyme analysis has become a powerful tool; but, for the sexual forms, breeding tests are still held to be of great importance too (e.g., see Nyberg 1981). Cryopreserved strains are, again, available (see below).
Isozyme patterns. Once again, the electrophoretic mobilities of the isozymes represent an excellent and convenient method for discrimination of individual species among the 17 Tetrahymena species currently comparising the pyriformis complex. The early work (Allen and Weremiuk 1971; Borden et al. 1973), on both asexual and sexual strains, set the stage for more recent studies (e.g. Borden et al. 1977; Nanney, Cooper et al. 1980; Nyberg 1981) that, in the main, have confirmed the data ammassed and the conclusions drawn by such pioneers as Bordern. Also SDS polyacrylamide gel electrophoresis of cytoskeletal proteins has supported some preceived relationships based on isoenzyme analysis and suggested that closer examination of other relationships may result in some taxonomic changes (Vaudaux et al. 1977; Williams 1983; Williams and Buhse 1983). Nanney, Cooper et al. (1980) raise some important points with respect to possible problems associated with "perfect" reproducibility of isozyme analysis results: choice, and source, of enzyme systems: factors of enzyme polymorphism; preference of isozyme used as the standard mobility reference; wide molecular divergence of the strains under comparative study; number of enzymes surveyed; and even the technical and procedural methodologies employed by different laboratories and/or different personnel. Details of procedures can be neither given nor discussed here. Techniques, as well as the result and data obtained, must be studied firsthand in the papers cited above by any new worker wishing to compare his or her fresh results, on either known or unknown strains, with findings in the earlier literature. Having authenticated reference strains now available on request (e.g., from ATCC) is of inestimable value to such new investigators: they should take full advantage of it. (ref. ID; 7704)
Morphological features. In general, morphological features of the various members of the pyriformis complex are too similar, or too variable both within and among species, to serve reliably in diagnosis of a given species or of a population of unknown tetrahymenas collected from the wild. One of the most interesting corticotypic characters in Tetrahymena, however, but one requiring good silver impregnation of multiple specimens, is its set of contractile vacuole pores, and their position may come to be quite useful in species determination (McCoy 1975; Nanney 1967, 1971; Nanney, Nyberg et al. 1980). The CVP positions are given as percentages of the distance around the organism from the first kinety (ciliary meridian) to the mean location of the pores themselves. The figures on such measurements are remarkably constant in some populations (e.g., see Frankel 1972). But, to date, they have been considered risky to use for species separation, especially for amicronucleate members of the complex (Nanney and McCoy 1976). Differences in body size have seemed valuable in the past in separation of some of the classical "amic" strains from others (Corliss 1953; Loefer 1952); but such a feature is not recommended for species discrimination among the current membership of the whole pyriformis complex. Use of combinations or of a "constellation" of morphological characters has also been suggested by the workers just cited (Corliss 1973; Loefer 1967), but such a recommendation was/is insufficient for application to the present overall problem. The total number of kinetosomes are tetrahymenid ciliate at a particular time in the cell cycle, under controlled laboratory growth conditions, may represent another feature of comparative value in species identification. However, the ranges in numbers overlap for certain (former) syngens of the pyriformis complex (Nanney et al. 1978; Nanney and Chow 1974), making this character one of questionable reliability. As in the case of Paramecium, and for ciliates in general, morphogenetic and ultrastructural features are of limited taxonomic value at the lower levels of classification (Corliss 1979, 1980), particularly at the sibling-species level. However, there is a vast and continually growing literature on Tetrahymena in areas of morphologenesis and ultrastructure, with many papers emphasizing both "form" and "function". Conceivably, some day some data on cortical patterns (as in the case of the contractile vacuole pores) and on the fine structure of the kinetid may prove to be worthwhile in identification of cryptic species. (ref. ID; 7704)
Ecological and biogeographical characteristics. While multiple strains of certain species within the pyriformis complex have been found within relatively restricted areas of the world (Elliott 1970, 1973; McCoy 1975; Nyberg 1981), deliberate attempts to make an exhaustive search of any region by systematic collecting have not been carried out. Concerning the kinds of fresh-water niches preferred, our information to date is also fragmentary. In short, our knowledge of the natural distribution of species of the T. pyriformis complex is even worse than it is for members of the P. aurelia complex. It is doubtful if collection site can ever be of broad value in taxonomically differentiating such cryptic ciliate species, but the carrying out of extensive collections would still be worthwhile for biogeographical reasons. (ref. ID; 7704)
Other features of possible use. Certain molecular approaches to taxonomy are more feasible for species of Tetrahymena than for Paramecium: for example, determination of DNA base ratios and nucleic acid hydridization experimentation. Comparative studies on the G + C content of species of the pyriformis complex have indeed been carried out (see Allen and Gibson 1973); and Nanney and McCoy (1976) included such data in their "chief characteristics" chart. Allen and Li (1974) have done some nucleotide sequencing work. Their results are important in revealing the large evolutionary discontinuities among species of the complex (Nanney 1983), but the approach would be neither so convenient nor feasible to apply in routine taxonomic separation of groups at the species level. Immunological procedures, important for other reasons in their own right (in ciliate genetics, etc.), also appear not to be suitable for taxonomic use in the case of species belonging to the pyriformis complex (Loefer and Scherbaum 1963). Immobilization antigens in Tetrahymena show an unsuitably large degree of genetic polymorphism (Nanney and McCoy 1976). Although all "sexual" species of the complex appear (or are assumed) to have a haploid number of five micronuclear chromosomes, idiogramming them at anaphase (Tiedtke 1982) might reveal interesting differences of value in the taxonomy of these tetrahymenas. Various physiological and biochemical traits (generally studied for non-taxonomic reasons) have been found to differ among certain pyriformis strains (Hill 1972; Holz et al. 1959; Levy 1973; Loefer 1967; McCashland and Johnson 1957; Nyberg 1974). But the data from such investigations, to date, are not generally applicable to the problem of recognizing the singular uniqueness of each species in the complex. In the recent work by Nyberg (1981), however, a much large variance in temperature tolerance was found among these species than in any of the wild stocks within a species: this represented a "physiological distinctness" of considerable potential taxonomic value at the species-level. Yet there was overlap in possible pairwise comparisons among the species, as Nyberg admits; and he states, further, his belief that "knowing the temperature tolerance of stock is not sufficient information for (its) unambiguous identification". Life cycle characteristics (in the genetic sense) are of possible diagnostic utility, but most of them need further study and extension to include the more "neglected" species before their potential value can be realized. Of course, as in the case of the P. aurelia species, "fruitful mating" remains an ideal - albeit sometimes difficult phenomenon to bring about, occasionally unreliable, and, of course, impossible with limited material - criterion for species identication within the sexual or syngenic moiety of the T. pyriformis complex. Mating type determination data (Sonneborn 1974) are useful but incomplete. Such additional attributes as the length of period of sexual immaturity, behavior of heterozygotes during vegetative growth, and behavior of the macronucleus during conjugation are still too little known to be of predictable taxonomic value, as Nanney and McCoy (1976) acknowledge. (ref. ID; 7704)
[Availability of Strains]: For authenticated material, as in the case of paramecium stocks, the two repositories most trustworthy are the American Type Culture Collection in Maryland, and the Culture Centre of Algae and Protozoa in Cambridge, England. A complete set of the members of the pyriformis complex is available only from the ATCC; in fact, the cryogenically preserved material there includes not only the 17 named tetrahymenas of this complex but also strains of phenoset D and of syngens 6 and 8 (the last two at present combined under the name of the much studied species, T. pigmentosa). Still additional groups and strains of the pyriformis complex, ones not yet formally described as separate species, are included among ATCC's holdings. A warning to researchers not to obtain "pedigreed" strains from sources outside the two collections cited is made in earnest, if one wishes to be absolutely certain of having a reliable reference strain for some precise investigation. Over the years, most unfortunately, inadvertent "mix-ups" have occurred in handling cultures, particularly of the early, now classical, amicronucleate strains: cultures have become contaminated (e.g., with a faster growing strain) and/or strain labels have been lost or interchanged, as already mentioned briefly above. To add to the confusion, cultures, bacterized or axenic, have been generously exchanged back and forth between laboratories, with no way of knowing where, by whom, or when mix-up may have occurred, so that tracing the "true" history of a given strain has now generally become completely impossible. To add to the dilemmna, in a few cases cultures have been known to have been replaced with fresh collections from the wild that were then assumed by the collector to be identical with the "old" strain!. (ref. ID; 7704)
[Proposed practical solutions]: As suggested in various of the preceding paragraphs, the problem of proper identification of species assignable to the (still growing) T. pyriformis complex is greater than it is in the case of the P. aurelia ciliates for at least these reasons: the pyriformis organisms are more heterogenous genetically, their breeding data are not always as reliable, some strains are amicronucleate, some are persistent selfers, and finally their very diversity and more widespread distribution requires more extensive study to insure accuracy in differentiating species within the overall group (Nanney 1983). Yet, since tetrahymenas are used in considerably greater number of kinds of biological studies than paramecia, they more often need - and on behalf of a greater variety of workers - to be correctly recongized taxonomically. (ref. ID; 7704)
For field biologists. Hydrobiogists or survey-ecologists of fresh-water habitats are bound to encounter tetrahymenas, small (one-third length of a paramecium and thus of much less volume) and relatively undistinguished though these ciliates are. They may be either amicronucleate or (potentially) sexual strains: this ought to be determined first, if other general characteristics have already suggested that the organism belongs to the pyriformis complex. Either phase microscopy should be employed on living material or, preferably, specimens should be brought to a laboratory, cultured on a simple proteose-peptone medium (e.g., 1% or 2% with the antibiotic streptomycin, 500 um/liter, added to keep down bacterial growth), and fixed and impregnated with silver by one of several possible techniques (see references in Corliss 1973, 1979). Unless an electrophoretic study can be carried out on the organism to prove the fact, it should not be identified as "Tetrahymena pyriformis (Ehrenberg, 1830) Lwoff, 1947, or named by any one of the earlier junior synonyms, such as "T. geleii", "Glaucoma pyriformis", or "G. pyriformis". If the ciliate is amicronucleate, perhaps the best that can be done today (unless electrophoretic data are obtained) is to call it "Tetrahymena sp.", with a footnote that it appears to be an amicronucleate member of the T. pyriformis complex. However, see our Addendum, in which the attractive concept of a "supraspecies" (proposed by Genermont and Lamote 1980) is discussed: using that alternative solution, one could label his or her material as 'Tetrahymena suprasp. pyriformis". If electrophoresis is used, then assignment to the proper phenoset (Nanney and McCoy 1976) can be made, unless the organism represents an entirely new form. If the population is micronucleated, then, with or without evidence of conjugation in the collected material, it would be best to call it, again, "Tetrahymena sp.", with the added note that presumably it is either a member of one of the already described "mating" species of the pyriformis complex or a new sibling species (but also see our Addendum, below, as mentioned in the preceding paragraph). The proper full specific name should be used, of course, if breeding analysis and/or electrophoretic evidence support(s) the choice of one of the known cryptic micronucleated species over any of the others. If the organism has been found in the hemocoel of some freshwater insect larva (sometimes adult, too), or in some other host, the problem is compounded. Amicronucleate members of the pyriformis complex adapt well to many such "parasitic" habitats; but a different already known species of Tetrahymena outside the pyriformis group may well be involved or even an altogether new species (e.g., see Batson 1983; Corliss 1960, 1961, 1972, 1973; Corliss et al. 1979; Corliss and Coats 1976; Golini and Corliss 1981; Lynn et al. 1981). Once again, as for Paramecium, standard protozoological field guides are of no aid in distinguishing the (now) real T. pyriformis from its many sibling species, micro- and amicronucleate forms alike. In fact, the protozoan ecologists' indispensable "bible", Kahl (1931), is particularly misleading since species of "Tetrahymena", a name not yet invented until 1940, are mixed with other groups, notably Glaucoma. (ref. ID; 7704)
For laboratory experimentalists. Exactly as advised in the case of the P. aurelia complex, workers who plan to carry out sophisticated experiments with results to be meaningful in comparison with those of other studies must use only properly identified material. If available old strains are suspect in any way or for any reason, then fresh cultures of authenticated material should be obtained from such reliable collections as the ATCC or the CCAP. If other, or newly isolated, strains are employed, they should be identified by enzyme analyses and given the appropriate designation or scientific name. If the organism does not "fit" into a known group, it might be best not to use it; but do not discard it! A culture should be sent to a recognized collection or to an experienced tetrahymenologist so that a comparative study can possibly be made to determine its probable relationship to other species in the complex. It should be noted here that electrophoretic studies have not yet been carried out on the dozen or so other micronucleated species of the whole genus Tetrahymena that are not members of the pyriformis complex (Corliss 1973, 1979). The results of such investigations, once available, may prove to be very interesting from comparative taxonomic and evolutionary points of view. (ref. ID; 7704)
For writeres, teachers, and editors. It is a disservice to science to knowingly perpetuate (as well as to perpetrate it in the first place) and erroneous taxonomic name in association with an organism, whether one does it in a published paper or, as a teacher, in a classroom or laboratory full of unsuspecting students. Such false biological information makes impossible the comparison of results with those of other investigators who have accurately identified their material. In the Materials and Methods sections of a paper, the exact name of the organism (including any appropriate strain or phenoset designation) should appear, an it source as well. Editors should be willing to help authors who are unsure of the exact information required. (ref. ID; 7704)
[Concluding remarks on the T. pyriformis problem]: There is (still) a species of the genus Tetrahymena named T. pyriformis. But it is now (since 1976) restricted to an amicronucleate ciliate sharing enzyme electrophoretic characteristic of only phenoset A of the entire pyriformis complex. Other "amics" are similarly assignable to other phenosets (B-E), three which (B, C, E) now bear separate taxonomic names of their own. Older strain designations for long-standing cultures of amicronucleate tetrahymenas are suspect and are thus no longer reliable: do not use them. The micronucleated (sexual, syngenic) former members of Tetrahymena pyriformis sensu lato now have their own separate taxonomic names, 10 established by Nanney and McCoy (1976) and three, more recently, by Nyberg (1981). It is highly likely that still more such species await naming, following discovery and proper characterization (by breeding test and/or appropriate enzyme analysis). It is advisable, as in the case of forms beloning to the Paramecium aurelia complex, that only authenticated strains (both "amic" and sexual ones are now available in the cryopreserved state) be used in comparative research work of a sophisticated genetic or biochemical nature. The "pyriformis-like" populations of tetrahymenas found "in the wild" in field work (e.g., during ecological or hydrobiological studies) are probably best labeled only as "Tetrahymena sp." with mention of their likely association with the pyriformis complex, unless/until precise laboratory identification tests can be carried out on them. As an alternative, a "supraspecific" name could be used, as disccused in our Addendum, below. (ref. ID; 7704)
[Addendum]: We are greatful to the Redacteur for permitting us to append a short section here concerning an excellent point brought to our attention by one of the reviewers of our manuscript, discussion of which however, would be difficult to incorporate directly to the pages of any preceeding sections. In effect, an alernative practical solution has been suggested for the problem of what name to use in identification of some sibling (jumelle) or syngenic species when sophisticated breeding or molecular techniques are not avaiable to the investgator (e.g., a field ecologist). The very recently proposed taxonomic-nomenclatural category of "supraspecies" - well described by its originators Genermont and Lamotte (1980), who acknowledge their indebtedness to nomenclaturist G. Bernardi - nicely links together taxonomically any group of species difficult to separate, one from the other, morphologically or ecologically. The term is not to be confused with the restrictive, little used, quite different category of "superspecies" (see Mayr 1969). Thus, instead of listing a population of organisms as "Paramecium sp." or "Tetrahymena sp.", indicating total ignorance of the precise (sibling) specific name to use and seemingly leaving only the genus as the first level of their identification, one could write: "Paramecium suprasp. aurelia" or "Tetrahymena suprasp. pyriformis". Usage of such terminology would clearly provide the reader with a "morphological type", as it were, but at an infrageneric (even infrasubgeneric) level. When/if the specific name is known, the new category could still be employed: for example, a biochemist might be working with Tetrahymena (suprasp. pyriformis) thermophila. In a way, the supraspecific category would replace the longer expressions "pyriformis complex" or "member of the pyriformis complex", the non-taxonomic notations recommended in a preceding section of this paper to field biologists, to be used as footnotes (in lists, tables, etc.) to the name Tetrahymena sp. One of the advantages of the idea is that it releases the term "complex" for informal usage at a still lower group level. Recall that Williams and Buhse (1983) have suggested that among the micronucleated members of the "T. pyriformis complex" one can recognize three well defined groups: the T. americanis complex, the T. borealis complex, and the T. thermophila complex. There appear to be very few disadvantages to this proposed practical solution, that is, using the supraspecies concept described above. Yet one, naturally, is that its very newness will, at first, make it unfamiliar and therefore possibly a little confusing to many readers. Also, the closeness of the spelling of the two words "supraspecies" and "superspecies" is unfortunate. From a taxonomic-nomenclatural point of view, however, we endorse with enthusiasm its future consideration by protologists. With respect to its usage with the two groups of ciliate sibling species under discussion in the present paper, only new serious problem arises. I is caused by the necessity (see Genermont and Lamotte 1980) of having a "nominate" species within each supraspecies; or, to put it another way, the Latin name of the supraspecies must be identical to the name of one (presumably the oldest) species included in the group. This causes no trouble in the case of Tetrahymena. T. (suprasp. pyriformis) pyriformis works very well. But for Paramecium, as discussed on earlier pages, there is no longer any taxonomic species P. aurelia and thus, legalistically, there can, at the moment, be no P. (suprasp. aurelia) aurelia! In their paper, our good French colleagues suggest rejection of Sonneborn's first binomen, P. primaurelia, replacing it with "P. aurelia", which would then allow a taxonomic-nomenclatural treatment parallel to that given for Tetrahymena above. But the matter cannot be handled so simply. Further discussion of this particular knotty and complex problem, however, is beyond the scope of the present paper. Its final proper resolution would involve, at the least, a carefully prepared lengthly pertition to the Intenational Commission on Zoological Nomenclature for future formal consideration by the commissioners. Unfortunately, at the present time, this restrict our giving complete support to the otherwsie attactive "alternative practical solution" discribed in this Addendum. (ref. ID; 7704)

Tetrahymena americanis (ref. ID; 65, 3882, 4005, 4035, 4147, 7115, 7390)
Syn; Tetrahymena pyriformis syngen 2
Description; Cytochrome c Oxidase Subunit I (cox-1) Barcode. (ref. ID; 7115)
Tetrahymena asiatica Simon, Meyer & Preparata, 1985 (ref. ID; 4147 original paper) reported author and year? (ref. ID; 65, 7115, 7390)
Syn; Tetrahymena pyriformis-complex
Description; Cytochrome c Oxidase Subunit I (cox-1) Barcode. (ref. ID; 7115)
Tetrahymena australis (ref. ID; 65, 3882, 4005, 4035, 4147, 7115, 7390)
Syn; Tetrahymena pyriformis syngen 11
Description; Cytochrome c Oxidase Subunit I (cox-1) Barcode. (ref. ID; 7115)
Tetrahymena bergeri Roque, de Puytorac & Savoie (ref. ID; 3789) reported author and year? (ref. ID; 191, 7115)
Description; Tetrahymena rostrata-complex. Histophagous ciliate. (ref. ID; 3789)
Cytochrome c Oxidase Subunit I (cox-1) Barcode. (ref. ID; 7115)
Tetrahymena borealis (ref. ID; 65, 190, 3882, 4005, 4035, 7115, 7390)
Syn; Tetrahymena pyriformis syngen 3
Description; Cytochrome c Oxidase Subunit I (cox-1) Barcode. (ref. ID; 7115)
Tetrahymena canadensis (ref. ID; 65, 190, 3882, 4005, 4035, 4147, 7115, 7390)
Syn; Tetrahymena pyriformis syngen 7
Description; Cytochrome c Oxidase Subunit I (cox-1) Barcode. (ref. ID; 7115)
Tetrahymena capricornis (ref. ID; 65, 3882, 4005, 4035, 7115, 7390)
Syn; Tetrahymena pyriformis syngen 12
Description; Cytochrome c Oxidase Subunit I (cox-1) Barcode. (ref. ID; 7115)
Tetrahymena caudata Simon, Meyer & Preparata, 1985 (ref. ID; 4147 original paper) reported author and year? (ref. ID; 7115)
See; Tetrahymena patula-complex
Description; Cytochrome c Oxidase Subunit I (cox-1) Barcode. (ref. ID; 7115)
Tetrahymena corlissi Thompson, 1955 (ref. ID; 3789) reported year? (ref. ID; 3698) reported author and year? (ref. ID; 65, 191, 7115)
Description; Tetrahymena rostrata-complex. Histophagous ciliate. (ref. ID; 3789)
Cytochrome c Oxidase Subunit I (cox-1) Barcode. (ref. ID; 7115)
Tetrahymena cosmopolitanis (ref. ID; 3882, 7115, 7390)
Syn; Tetrahymena pyriformis syngen 4
Description; Cytochrome c Oxidase Subunit I (cox-1) Barcode. (ref. ID; 7115)
Tetrahymena elliotti Nanney & McCoy, 1976 (ref. ID; 6884) reported author and year? (ref. ID; 65, 3882, 4035, 7390)
Remarks; Previously T. pyriformis GL, phenoset B, of Borden et al. 1973; strain L1630/1c of the Culture Centre of Algae and Protozoa, Cambridge, England. (ref. ID; 6884)
Tetrahymena empidokyrea Jerome, Simon & Lynn, 1996 (ref. ID; 7267) reported author and year? (ref. ID; 7115)
Description; Cytochrome c Oxidase Subunit I (cox-1) Barcode. (ref. ID; 7115)
Tetrahymena empidokyrea n.sp. cells that were grown in PPYE and then fixed and stained were pyriform, and cells that were not cultures (i.e., fixed in Champy's fluid within a few hours of release from the host) were more roundly pyriform. Tetrahymena empidokyrea n.sp. cells are morphologically indistinguishable from previously described species in the T. pyriformis complex. Mating experiments do distinguish this new species. Tetrahymena empidokyrea n.sp. cultured in PPYE ranged in length from 32 to 52 um and in width from 18 to 32 um, with 16-19 somatic kineties and 1 or 2 post-oral kineties. (ref. ID; 7267)
[Phylogenetic position]: The complete SSrRNA sequence for T. empidokyrea n.sp. is 1747 nucleotides. This sequence has been deposited with the GENBANK data library under Accession No. U386222. The maximum parsimony analysis of 121 phylogenetically informative sites produced 42 equally parsimonious trees. The genus Tetrahymena is depicted as a monophyletic group, including the new species, T. empidokyrea n.sp. The species in the genus Tetrahymena are divided into two main lineages: (1) the T. australis group, including T. australis, T. capricornis, T. nanneyi, T. pigmentosa, T. patula, and T. hegewischi; and (2) the T. borealis group, including T. corlissi, T. malaccensis, T. thermophila, T. tropicalis, T. canadensis, T. borealis, and T. pyriformis. These lineages were supported by relatively high bootstrap values, 76 and 68%, respectively. However, low bootstrap values, within the these groups demonstrate that the relationship amongst species within a lineage is uncertain. Additionally, there is low bootstrap support for the placement of T. empidokyrea n.sp.: in each of the 42 equally parsimonious trees, T. empidokyrea n.sp. was found in one of two positions, either as the sister-species to the T. australis group or basal to all Tetrahymena spp. The latter position, proposed by the parsimony analysis, agrees with that suggested by the maximum likelihood analysis, which also supports monophyly of the genus Tetrahymena. Structural similarities for each pair of species' SSrDNA sequences were obtained and used to determine evolutionary distances, which were used to construct a distance tree. There were 490 sites of the 1812 in the total alignment where substitutions occurred. Here also, the genus Tetrahymena is a monophyletic group, divided into two main lineages. In the distance analysis, T. empidokyrea n.sp. is the sister taxon the T. asutralis group. In the distance analysis, T. empidokyrea n.sp. is the sister-taxon to the T. australis group. This is in agreement with one of the two positions proposed on the basis of the maximum parismony analysis and in contrast to the position proposed for T. empidokyrea n.sp. on the basis of the maximum likelihood analysis, where it is basal to all Tetrahymena species. (ref. ID; 7267)
Etymology; Since specimens of T. empidokyrea n.sp. were found in adult Aedes sp. mosquitoes, we derived the name from empis, m, Greek, "mosquito, gnat," and kyreo, Greek, "light upon, find." (ref. ID; 7267)
Type locality; Wild Goose Woods, Arboretum, University of Guelph, Guelph, Ontario, Canada (43 degrees 33.50'N, 80 degrees 11.46'W). (ref. ID; 7267)
Type specimens; Two type cultures of T. empidokyrea n.sp. (Accession Nos. 50595 and 50596) have been submitted to the American Type Culture Collection (Bethesda, Maryland, U.S.A.). Chatton-Lwoff silver-stained type slides (USNM 47826, USNM 47827) of T. empidokyrea n.sp. were submitted to the Ciliate Type Slide Collection of the National Museum of Natural History (Smithsonian Institution, Washigton, D.C.). (ref. ID; 7267)
Tetrahymena farleyi (ref. ID; 7115)
Description; Cytochrome c Oxidase Subunit I (cox-1) Barcode. (ref. ID; 7115)
Tetrahymena hegewischi (ref. ID; 65, 154, 4005, 7115, 7390)
Syn; Tetrahymena pyriformis syngen 5
Description; Cytochrome c Oxidase Subunit I (cox-1) Barcode. (ref. ID; 7115)
Tetrahymena hyperangularis (ref. ID; 65, 190, 3882, 4005, 4035, 7115, 7390)
Syn; Tetrahymena pyriformis syngen 10
Description; Cytochrome c Oxidase Subunit I (cox-1) Barcode. (ref. ID; 7115)
Tetrahymena leucophrys Williams, Buhse Jr. & Smith, 1984 (ref. ID; 4119 original paper, 4147) reported author and year? (ref. ID; 65, 7115)
Description; Cytochrome c Oxidase Subunit I (cox-1) Barcode. (ref. ID; 7115)
Tetrahymena limacis (Warren) (ref. ID; 1618, 3789) reported author and year? (ref. ID; 65, 7115)
Description; In liver and other visceral organs of the slug Deroceras reticulatum; the parasitic phase is cucumber-shaped with apiculate anterior end; the free-living organisms are pyriform, somewhat pointed anteriorly; cytostome at about one-fourth from the anterior end, with an undulating membrane and three membranelles; 32-40 ciliary rows (Kozloff, 1946). As was mentioned above, experimentally T. pyriformis can infect slugs without changing morphological characteristic except the size. The ciliate was further found in terrestrial gastropods, Monadenia fidelis and Prophysaon andersoni. Corllis (1952) held that Kozloff's form is different from T. limacis and called it T. faurei. (ref. ID; 1618)
See Tetrahymena rostrata-complex (ref. ID; 3789)
Cytochrome c Oxidase Subunit I (cox-1) Barcode. (ref. ID; 7115)
Measurements; 33-68 (55) by 18-35 (27) um; those from cultures measure 28-68 (44) by 17-42 (27) um. (ref. ID; 1618)
Tetrahymena malaccensis Simon, Meyer & Preparata, 1985 (ref. ID; 4147 original paper) reported author and year? (ref. ID; 65, 190, 7115, 7390)
See; Tetrahymena pyriformis-complex
Description; Cytochrome c Oxidase Subunit I (cox-1) Barcode. (ref. ID; 7115)
Tetrahymena mimbres (ref. ID; 65, 4395, 7115, 7390)
Description; Cytochrome c Oxidase Subunit I (cox-1) Barcode. (ref. ID; 7115)
Tetrahymena mobilis (ref. ID; 7115)
Description; Cytochrome c Oxidase Subunit I (cox-1) Barcode. (ref. ID; 7115)
Tetrahymena nanneyi Simon, Meyer & Preparata, 1985 (ref. ID; 4147 original paper) reported author and year? (ref. ID; 65, 190, 4611, 7115, 7390)
See; Tetrahymena pyriformis-complex
Description; Cytochrome c Oxidase Subunit I (cox-1) Barcode. (ref. ID; 7115)
Tetrahymena nipissingi (ref. ID; 65, 154, 4005, 7115, 7390)
Syn; Tetrahymena pyriformis syngen 14
Description; Cytochrome c Oxidase Subunit I (cox-1) Barcode. (ref. ID; 7115)
Tetrahymena paravorax Corliss, 1957 (ref. ID; 7539, 7602) reported year? (ref. ID; 3828) reported author and year? (ref. ID; 65, 191, 3893, 7115)
Description; Cytochrome c Oxidase Subunit I (cox-1) Barcode. (ref. ID; 7115)
Tetrahymena patula (ref. ID; 65, 190, 191, 7115)
Description; Cytochrome c Oxidase Subunit I (cox-1) Barcode. (ref. ID; 7115)
Tetrahymena patula (Ehrenberg, 1830) Corliss, 1951 (ref. ID; 3959) reported year? (ref. ID; 1335, 1618, 2100)
Syn; Leucophrys patula Ehrenberg (ref. ID; 1618)
Description; Broadly pyriform; occasionally small forms occur; cytostome pyriform, about one-third the body length; 40-45 ciliary meridians; macronucleus irregularly ovoid; a micronucleus attached to micronucleus; carnivorous, but may be cultured in sterile media; fresh water. (ref. ID; 1618)
Measurements; 80-160 um long. (ref. ID; 1618)
Tetrahymena pigmentosa (ref. ID; 65, 190, 3882, 4005, 4035, 7115, 7390)
Syn; Tetrahymena pyriformis syngen 6, 8
Description; Cytochrome c Oxidase Subunit I (cox-1) Barcode. (ref. ID; 7115)
Tetrahymena pyriformis (Ehrenberg) (ref. ID; 3698, 5462) or (Ehrenberg) Lwoff (ref. ID; 1219, 1335, 1618, 1629, 2100, 2245), (Ehrenberg) Lwoff, 1947 (ref. ID; 3560) reported author and year? (ref. ID; 65, 190, 191, 5923, 7115, 7390, 7699)
Syn; Glaucoma pyriformis (Ehrenberg) Schewiakoff (ref. ID; 1219); Tetrahymena geleii Furgason (ref. ID; 1618)
Description; Body ovoid and uniformly ciliated; mouth roughly triangular, longitudinal axis of the buccal cavity parallel to that of the cell itself; buccal cavity containing an undulating membrane on the right side and an adoral zone of 3 membranelles on the left; the spherical macronucleus is situated medially and is usually accompanied by 1 micronucleus; 1 contractile vacuole near the posterior end. (ref. ID; 1219)
Seventeen to twenty-three ciliary meridians; pyriform cytostome about one-tenth the body length; with or without micronucleus; bacteria-feeder; in fresh water. (ref. ID; 1618)
Cytochrome c Oxidase Subunit I (cox-1) Barcode. (ref. ID; 7115)
An ultrastructural study of the macronucleus. (ref. ID; 7699)
Notes; Morphological changes during the growth cycle of axenic and monoxenic Tetrahymena pyriformis strain 30008 (WH-14, syngen I, mating type II). (ref. ID; 5923)
Measurements; Length 25-90 um. (ref. ID; 1219)
40-60 um long. (ref. ID; 1618)
Tetrahymena rostrata (Kahl) (ref. ID; 1618, 3789) or (Kahl, 1926) Corliss, 1952 (ref. ID; 4861) reported author and year? (ref. ID; 65, 7115)
Description; In fresh water (often in dead rotifers); Kozloff (1957) found this species in the renal organ of the garden slug, Deroceras reticulatum and established axenic cultures. (ref. ID; 1618)
Histophagous ciliate. (ref. ID; 3789)
Cytochrome c Oxidase Subunit I (cox-1) Barcode. (ref. ID; 7115)
Measurements; 60-80 um long. (ref. ID; 1618)
Tetrahymena setosa (ref. ID; 65, 3638, 4108, 7115)
Syn; Tetrahymena setifera (ref. ID; 3638, 4108)
Description; Cytochrome c Oxidase Subunit I (cox-1) Barcode. (ref. ID; 7115)
Tetrahymena shanghaiensis (ref. ID; 7115)
Description; Cytochrome c Oxidase Subunit I (cox-1) Barcode. (ref. ID; 7115)
Tetrahymena silvana Simon, Meyer & Preparata, 1985 (ref. ID; 4147 original paper) reported author and year? (ref. ID; 65, 7115)
See; Tetrahymena patula-complex
Description; Cytochrome c Oxidase Subunit I (cox-1) Barcode. (ref. ID; 7115)
Tetrahymena sonneborni (ref. ID; 65, 154, 4005, 7115, 7390)
Syn; Tetrahymena pyriformis syngen 13
Description; Cytochrome c Oxidase Subunit I (cox-1) Barcode. (ref. ID; 7115)
Tetrahymena stegomyiae (Keilin) (ref. ID; 3789)
Description; See Tetrahymena rostrata-complex. (ref. ID; 3789)
Tetrahymena thermophila (ref. ID; 65, 190, 191, 3648, 3894, 3980, 3981, 7115, 7390, 7667)
Syn; Tetrahymena pyriformis syngen 1 (ref. ID; 3873, 3882, 3894, 3905, 3924)
Description; Cytochrome c Oxidase Subunit I (cox-1) Barcode. (ref. ID; 7115)
The pregamic divisions of the micronucleus in conjugation of Tetrahymena thermophila strains CU 329 were reinvestigated using a modified ammoniacal silver (AS) staining technique. (ref. ID; 7667)
Tetrahymena tropicalis (ref. ID; 65, 190, 3882, 4005, 4035, 7115, 7390)
Syn; Tetrahymena pyriformis syngen 9
Description; Cytochrome c Oxidase Subunit I (cox-1) Barcode. (ref. ID; 7115)
Tetrahymena vorax Kidder, 1941 (ref. ID; 4123, 4210, 4217), (Kidder et al., 1940) Kidder, 1941 (ref. ID; 388) or (Kidder, Lilly & Claff) (ref. ID; 1618) reported author and year? (ref. ID; 65, 191, 7115, 7612)
Syn; Glaucoma vorax Kidder, Lilly & Claff (ref. ID; 1618)
Description; Microstomal and macrostomal cell types of the polymorphic ciliated protozoon Tetrahymena vorax utilize different food sources and thus display differences in size and shape of the food-gathering structures. The particulate-feeding microstomal form, the cell type normally present during vegetative growth in axenic culture, possesses a small oral apparatus with average dimensions of 10.6 x 5.7 um. The structure of the microstomal oral apparatus is similar to that of members of the T. pyriformis complex and like T. pyriformis. In contrast, the potentially carnivorous macrostomal cell type has a larger oral apparatus with average dimensions of 29 x 23 um, capable of engulfing prey ciliates, and a large prey receptacle, the cytopharyngeal pouch, which develops as a part of the cellular phenotype. Under normal feeding conditions, the cytopharyngeal pouch separates from the oral region only after a prey protozoon has been ingested. (ref. ID; 388)
[Macrostomal Form]: The buccal cavity of the Tetrahymena vorax macrostomal cell type is located on the anterior ventral surface with the length of the cavity representing about one-fourth to one-third of the length of the cell. The anterior, right, and posterior margins of the buccal overture are curved, but the left margin is relatively straight. The buccal overture usually dips at the junction of the posterior and left margins; in certain orientations this dip appears to result from the projection of the buccal overture outward, creating a lip. The buccal overture slopes ventrally from the anterior to the posterior margin so that the extreme anterior end of the cell does not overhang all of the posterior part of the cavity. The oral apparatus may be divided into three parts, that anterior portion between the anterior ventral margin and the anterior edge of the cytostome, the large cytostomal opening, and the posterior surface. Near the anterior ventral margin, the cavity is shallow with the wall slightly rounded. The surface of the cavity slopes dorsally from the anterior ventral margin and then turns toward the anterior margin of the cytostome. This turn is rounded with the exception of the region below membranelle 3 (M3) near the right side of the cavity, where the turn is sharp. The depth at the turn in the central part of the cavity, measured from a line between the anterior and posterior margins of the buccal overture, is approximately 10-11 um. However, both the size and depth of the oral cavity vary among cells within a macrostomal population. The undulating membrane, oral ribs, and membranelle 1 (M1) originate near the anterior ventral margin of the oral apparatus. Membranelle 2 (M2) and membranelle 3 (M3) begin a short distance below M1. The kinetosomes of the three membranelles that are located in the cytoplasm of the sloping anterior surface are oriented so that the cilia project toward the posterior end of the cavity. Membranelle 1 is adjacent to the straight left wall, in a trough formed by the left wall and the left side of a plateau on which M2 is located. The surface of the plateau for M2 projects into the cavity so that this membranelle is oriented toward the right side of the cavity. The position of M1 and M2 in longitudinal sections in the sagittal plane and in transverse sections and the decreasing height of the left side of the plateau for M2 from the anterior to posterior end indicate that M1 and M2 also are situated at an angle to each other along their length. The anterior wall is straight between M2 and M3, which is located in a trough near the right side of the cavity. The right wall, lined by the oral ribs, is slightly concave near the anterior margin of the oral cavity but curves outward into the cavity along the length of M3. The cytostome or aperture in the surface that comprises the entrance into the cytopharyngeal pouch occupies most of the remainder of the oral apparatus. This opening is relatively circular and measures approximately 15-16 um in diameter. In transverse sections through the center of the cytostome and in longitudinal sections through the frontal plane, the opening encompasses most of the width of the cavity between the right and left walls. The posterior wall of the buccal cavity consists of a small curved region between the posterior margin of the cytostome and the posterior end of the buccal overture. (ref. ID; 388)
Form and size vary; bacteria-feeders elongate pyriform, 50-75 um long; saprozoic forms fusiform, 30-70 um long, decreasing in size with the age of culture; sterile particle-feeders, 60-80 um long; carnivorous and cannibals broadly pyriform, 100-250 um long; nineteen to twenty-one ciliary meridians; macronucleus ovoid, central; in carnivorous, outline irregular; apparently without micronucleus; pond water. Polymorphism. (ref. ID; 1618)
The polymorphic ciliate Tetrahymena vorax Kidder, 1941 is representative of ciliate species that offer a unique opportunity to investigate two different forms of phagocytosis in cells with the same genotype. The microstomal cell type is a particle-feeder and forms small vacuoles sequentially; the carnivorous macrostomal form, which possesses a large cytopharyngeal pouch as part of the cellular phenotype, forms a single large vacuole upon ingestion of a prey protozoon. Transformation from the microstomal to the macrostomal cell type may be induced by several methods, including subjecting cells in a medium with low nutrient concentrations to a series of heat shock followed by washing cells into non-nutrient medium. Transformation involves the resorption of the microstomal oral apparatus and the formation of the larger oral apparatus of the macrostomal cell type. Resorption and replacement being several hours before the appearance of the cytopharyngel pouch, which develops during the last 30 min and which complete the transformation. Food vacuole cannot occur between oral resorption and development of the pouch. (ref. ID; 4217)
Cytochrome c Oxidase Subunit I (cox-1) Barcode. (ref. ID; 7115)