Licnophora auerbachii, from Cohn (1866); a = attachment disk, m = mouth, p = adoral region.

Belongs within: Alveolata.
Contains: Euplotia, Choreotrichida, Oligotrichida, Stichotrichida, Anteholosticha, Caudiholosticha.

A selection of ciliates
Published 18 December 2007
Euplotes, from A Micronaturalist’s Notebook.

Of all the groups of unicellular or paucicellular (excuse the neologism) eukaryotes generally lumped under the heading of ‘protozoa’ or ‘protists’, ciliates are one of the most noteworthy. Together with sporozoans, they were one of the very few groups to be recognised as distinctive* before the microbial classificatory revolution that was permitted by the appearance of SEM and molecular phylogeny. Through the example of Paramecium, they are also one of the few protist groups whose existence is widely known by the general public. While other prostists such as many flagellate** groups tend to be morphologically fairly plain, ciliates attain a diversity of form and complexity that seems incredible for unicellular organisms.

*Except for an unfortunate tendency for the non-ciliate Stephanopogon to keep trying to mooch its way into the ciliate party. Researchers still have pretty much no idea what to do with Stephanopogon, but the ciliates are adamant that they want nothing to do with it.

**Pre-revolution classifications generally divided protozoans on the basis of locomotory structures between flagellates (with flagella), amoebae (pseudopods), ciliates (cilia) and sporozoans (parasitic taxa without locomotory structures). While it is well-recognised by now that these divisions are largely artificial*** (as is the term ‘protozoa’ itself), they retain a certain degree of utility as descriptive conveniences (as does ‘protozoa’), though ‘amoeba’ should probably be passed over for ‘amoeboid’ so as not to cause confusion with the actual genus Amoeba. Also, while light microscopists distinguished flagella (relatively long and few) and cilia (relatively short and usually arranged in tracts), there is no real difference between the two. Some researchers would prefer to refer to all such structures in eukaryotes as ‘cilia’, reserving the term ‘flagella’ for bacterial locomotory structures, which are very different.

***Especially as many protists have both amoeboid and flagellate stages in their life cycles.

While the new technologies allowed ciliates as a whole to retain their integrity, they did incite a bit of reshuffling within the clade. Earlier classifications emphasised features of the oral apparatus, but from the 1980s the importance of ultrastructural characters such as arrangement of cilia was recognised (Lynn 2003). With the addition of molecular data, the ciliates settled (a little uneasily) down into eleven or so classes, some of them well-supported by both molecular and morphological data, some by only one or the other. It is with one of these classes, the Spirotricha, that we concern ourselves today.

The Spirotricha are a diverse bunch and support for them as a total group is, admittedly, fairly low (though support increases if the divergent Protocruzia is left out of the mix). The classic feature of the spirotrichs are the cirri—bunches of cilia fused into tendril-like structures, which can be seen fairly well in the image at the top of this section. Not all taxa united molecularly with spirotrichs possess cirri but features of macronuclear* division also support the grouping.

*An individual ciliate possesses multiple nuclei—one small micronucleus and one or more larger macronuclei. The macronuclei are involved in the day-to-day production of enzymes and such, while the micronucleus is involved in reproduction. When conjugation (sexual reproduction) occurs, the macronuclei break down and only the micronucleus is propagated. The macronuclei are then regenerated from the daughter micronuclei (see here for a more detailed and accurate description—like many so-called ‘simple’ organisms, ciliates make up for simplicity of structure by indulging in obscenely complicated life cycles).

Euplotes is one of the best-known of the spirotrichs. The figure above well illustrates how Euplotes uses its cirri to walk along the substrate, though they can also be used for swimming. Euplotes is a predator of other ciliates, and as such has a rather large oral cavity. Its voracity in feeding can be remarkable—Kloetzel noted in 1974 that “In extreme cases (with small Tetrahymena, which are eaten much more rapidly than large ones) a Euplotes cell can ingest 17 Tetrahymena within 5 min, representing an area of food vacuole membrane approximately twice that of the entire Euplotes surface”. Trust me, I’m fighting the urge to add exclamation marks after that one.

Tintinnid, imaged by Fiona Scott from Australian Antarctic Division.

Spirotrichs also include the only ciliate group to have a significant fossil records, the tintinnids. Unlike other ciliates, tintinnids form a lorica (a vase-shaped shell) that may be preserved after the death of the organism. A detailed taxonomy exists of tintinnids based mainly on lorica structure and composition, and it has been suggested that tintinnids with agglutinated loricas are basal to those with hyaline loricas. However, studies based on living tintinnids show that different lorica types may be possessed by species with the same or similar ciliary arrangements, and there does not appear to be a close correlation between lorica structure and ultrastructure of the living organism (Agatha & Strüder-Kypke 2007).

Systematics of Spirotricha
<==Spirotricha [Spirotrichea]
    |  i. s.: KiitrichidaeT87 [ProtohypotrichiaAS12]
    |           |--Caryotricha Kahl 1932T87
    |           `--Kiitricha Nozawa 1941T87
    |  `--Licnophoridae [Licnophoria, Licnophorida, Lichnophorina]AB19
    |       |--ProlicnophoraAB19
    |       `--LicnophoraL03
    |            |--L. auerbachii (Cohn 1866) [=Trichodina auerbachii; incl. L. asterisci Guber 1884]BK77
    |            |--L. cohniG84
    |            |--L. lyngbycola Fauré-Fremiet 1937SW03
    |            `--L. macfarlandiL03
    `--+--Phacodinium Prowazek 1900L03, AS12 [Phacodiniidia]
       |    `--P. metchnikoffiL03
       `--+--Tetmemena pustulataL03 [=Stylonychia pustulataAS-K07; incl. Oxytricha bifariaFMA07]
               |--Oligotrichia [Oligotrichea]A04
               |    |--ChoreotrichidaA04
               |    `--OligotrichidaA04
               `--Hypotrichia [Hypotricha, Hypotrichea, Hypotrichida, Stichotrichia]AS12
                    |  i. s.: Balladina euplotesD86
                    |         Allotricha Sterki 1878T87
                    |         Balladinopsis Gosh 1921T87
                    |         Banyulsella Dragesco 1953T87
                    |         Hemiholosticha von Gelei 1954T87
                    |         Klonostricha Vuxanovici 1963T87
                    |         Paraeuplotes Wichterman 1942T87
                    |         Plesiotricha Dragesco 1970T87
                    |         Prooxytricha Poche 1913T87
                    |         Psilotrix Gourret & Roeser 1888T87
                    |         Stichochaeta Cohn 1886T87
                    |           `--S. pediculiformisG84
                    |         Stylonethes Sterki 1878T87
                    |         Orthodon Gruber 1884G84
                    |           `--*O. hamatus Gruber 1884G84
                    |         AegyriaG84
                    |           |--A. monostylaG84
                    |           `--A. olivaG84
                    |         Stylocoma Gruber 1884G84
                    |           `--*S. oriformis Gruber 1884G84
                    |         Rigidothrix goiseriFMA07
                         |--Pseudourostyla [Pseudourostylidae]AB19
                         |    `--P. cristataOC09
                         |    |--BergeriellaAB19
                         |    `--NeourostylopsisAB19
                         |    |--Hemicycliostyla Stokes 1886T87
                         |    `--AustralothrixAB19
                         |    |--Keronella Wiackowski 1985T87
                         |    |--Thigmokeronopsis Wicklow 1981T87
                         |    |--ApoholostichaAB19
                         |    `--Pseudokeronopsis Borror & Wicklow 1983T87
                         |         `--P. rubraMB03
                              |--Bakuella Agamaliev & Alekperov 1976T87
                              |--Isosticha Kiesselbach 1936T87
                              |--Neokeronopsis Warren et al. 2002B03
                              |--Afrothrix Foissner 1999B03
                              |--Balladyna Kowaleski 1882T87
                              |--Balladynella Stiller 1974 non Theiss. & Syd. 1918 (ICBN)T87
                              |--Coniculostomum Njine 1978T87
                              |    `--C. monilataFMA07
                              |--Onychodromopsis Stokes 1887T87
                              |--Parurosoma von Gelei 1954T87
                              |--Trachelochaeta Sramek-Husek 1954T87
                              |--Trichotaxis Stokes 1891T87
                              |--Wallackia Foissner 1977T87
                              |--Urostyla Ehrenberg 1830T87
                              |    `--U. grandis Ehrenberg 1838T87
                              |--Laurentiella Borror 1972T87
                              |    `--L. strenua [incl. L. acuminata]FMA07
                              `--Biholosticha Berger 2003B03
                                   |--*B. discocephalus (Kahl 132) [=Holosticha discocephalus]B03
                                   `--B. ‘arenicola’ (Dragesco 1963) [=Holosticha arenicola non Kahl 1932]B03

*Type species of generic name indicated


[AB19] Adl, S. M., D. Bass, C. E. Lane, J. Lukeš, C. L. Schoch, A. Smirnov, S. Agatha, C. Berney, M. W. Brown, F. Burki, P. Cárdenas, I. Čepička, L. Chistyakova, J. del Campo, M. Dunthorn, B. Edvardsen, Y. Eglit, L. Guillou, V. Hampl, A. A. Heiss, M. Hoppenrath, T. Y. James, A. Karnkowska, S. Karpov, E. Kim, M. Kolisko, A. Kudryavtsev, D. J. G. Lahr, E. Lara, L. Le Gall, D. H. Lynn, D. G. Mann, R. Massana, E. A. D. Mitchell, C. Morrow, J. S. Park, J. W. Pawlowski, M. J. Powell, D. J. Richter, S. Rueckert, L. Shadwick, S. Shimano, F. W. Spiegel, G. Torruella, N. Youssef, V. Zlatogursky & Q. Zhang. 2019. Revisions to the classification, nomenclature, and diversity of eukaryotes. Journal of Eukaryotic Microbiology 66: 4–119.

[AS12] Adl, S. M., A. G. B. Simpson, C. E. Lane, J. Lukeš, D. Bass, S. S. Bowser, M. W. Brown, F. Burki, M. Dunthorn, V. Hampl, A. Heiss, M. Hoppenrath, E. Lara, E. Le Gall, D. H. Lynn, H. McManus, E. A. D. Mitchell, S. E. Mozley-Stanridge, L. W. Parfrey, J. Pawlowski, S. Rueckert, L. Shadwick, C. L. Schoch, A. Smirnov & F. W. Spiegel. 2012. The revised classification of eukaryotes. Journal of Eukaryotic Microbiology 59 (5): 429–493.

[A04] Agatha, S. 2004. A cladistic approach for the classification of oligotrichid ciliates (Ciliophora: Spirotricha). Acta Protozoologica 43: 201–217.

[AS-K07] Agatha, S. & M. C. Strüder-Kypke. 2007. Phylogeny of the order Choreotrichida (Ciliophora, Spirotricha, Oligotrichea) as inferred from morphology, ultrastructure, ontogenesis, and SSrRNA genes sequences. European Journal of Protistology 43 (1): 37–63.

[BK77] Barel, C. D. N., & P. G. N. Kramers. 1977. A survey of the echinoderm associates of the north-east Atlantic area. Zoologische Verhandelingen 156: 1–159.

[B03] Berger, H. 2003. Redefinition of Holosticha Wrzesniowski, 1877 (Ciliophora, Hypotricha). European Journal of Protistology 39 (4): 373–379.

[D86] Detcheva, R. 1986. Ciliata interstitiels, essentiellement des sables marins. In: Botosaneanu, L. (ed.) Stygofauna Mundi: A Faunistic, Distributional, and Ecological Synthesis of the World Fauna inhabiting Subterranean Waters (including the Marine Interstitial) pp. 21–29. E. J. Brill/Dr W. Backhuys: Leiden.

[FMA07] Foissner, W., H. Müller & S. Agatha. 2007. A comparative fine structural and phylogenetic analysis of resting cysts in oligotrich and hypotrich Spirotrichea (Ciliophora). European Journal of Protistology 43: 295–314.

[G84] Gruber, A. 1884. Die Protozoen des Hafens von Genua. Verhandlungen der Kaiserlichen Leopoldinisch-Carolinischen Deutschen Akademie der Naturforscher [Nova Acta Academiae Caesareae Leopoldino-Carolinae Germanicae Naturae Curiosorum] 46 (4): 473–539, pls 7–11.

Kloetzel, J. A. 1974. Feeding in ciliated protozoa. I. Pharyngeal disks in Euplotes: a source of membrane for food vacuole formation? Journal of Cell Science 15: 379–401.

[L03] Lynn, D. H. 2003. Morphology or molecules: how do we identify the major lineages of ciliates (phylum Ciliophora)? European Journal of Protistology 39 (4): 356–364.

[MB03] Miyake, A., F. Bounanno, P. Saltalamacchia, M. E. Masaki & H. Ito. 2003. Chemical defence by means of extrusive cortical granules in the heterotrich ciliate Climacostomum virens. European Journal of Protistology 39 (1): 25–36.

[OC09] Okamoto, N., C. Chantangsi, A. Horák, B. S. Leander & P. J. Keeling. 2009. Molecular phylogeny and description of the novel katablepharid Roombia truncata gen. et sp. nov., and establishment of the Hacrobia taxon nov. PLoS One 4 (9): e7080.

[SW03] Song, W., A. Warren, D. Ji, M. Wang & K. A. S. Al-Rasheid. 2003. New contributions to two heterotrichous ciliates, Folliculina simplex (Dons, 1917), Condylostoma curva Burkovsky, 1970 and one licnophorid, Licnophora lyngbycola Fauré-Fremiet, 1937 (Protozoa, Ciliophora): descriptions of morphology and infraciliature. Journal of Eukaryotic Microbiology 50 (6): 449–462.

[T87] Tuffrau, M. 1987. Proposition d’une classification nouvelle de l’ordre Hypotrichida (Protozoa, Ciliophora), fondée sur quelques données récentes. Annales des Sciences NaturellesZoologie et Biologie Animale, ser. 13, 8: 111–117.

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