Ciliate: Difference between revisions

Revision as of 00:02, 28 December 2005

Latest revision as of 18:59, 17 July 2025

(714 intermediate revisions by more than 100 users not shown)

Line 1:

{{About|the protozoan phylum Ciliophora|the type of ciliate cells in general|Ciliate cells|the type of leaf margin|Glossary of leaf morphology#Edge}}

{{Taxobox_begin | color = khaki | name = Ciliates}}

{{short description|Taxon of protozoans with hair-like organelles called cilia}}

{{Taxobox_image | image = [[Image:Paramecium.jpg|200px|Paramecium]] | caption = ''[[Paramecium]]''}}

{{Automatic taxobox

{{Taxobox_begin_placement | color = khaki}}

| fossil_range = {{fossilrange|630|0|[[Ediacaran]]–[[Holocene|Recent]]}}

{{Taxobox_regnum_entry | taxon = [[Protist]]a}}

| image = Ciliate collage.jpg

{{Taxobox_phylum_entry | taxon = '''Ciliophora'''}}<br><small>[[Doflein]] 1901 ''emend.''</small>

| image_caption = Some examples of ciliate diversity. Clockwise from top left: ''[[Lacrymaria (ciliate)|Lacrymaria]]'', ''[[Coleps]]'', ''[[Stentor (ciliate)|Stentor]]'', ''[[Dileptus]]'', ''[[Paramecium]]''

{{Taxobox_end_placement}}

| taxon = Ciliophora

{{Taxobox_section_subdivision | color = khaki | plural_taxon = Classes & Subclasses}}

| authority = [[Doflein]], 1901 ''emend.''

Class [[Karyorelictea]]<br>

| subdivision_ranks = Subphyla and classes

Class [[Heterotrich]]ea (e.g. ''[[Stentor (genus)|Stentor]]'')<br>

| subdivision_ref = <ref name=Gao2016>{{Cite journal|last1=Gao|first1=Feng|last2=Warren|first2=Alan|last3=Zhang|first3=Qianqian|last4=Gong|first4=Jun|last5=Miao|first5=Miao|last6=Sun|first6=Ping|last7=Xu|first7=Dapeng|last8=Huang|first8=Jie|last9=Yi|first9=Zhenzhen|date=2016-04-29|title=The All-Data-Based Evolutionary Hypothesis of Ciliated Protists with a Revised Classification of the Phylum Ciliophora (Eukaryota, Alveolata)|journal=Scientific Reports|language=en|volume=6|doi=10.1038/srep24874|issn=2045-2322|pmc=4850378|pmid=27126745|article-number=24874|bibcode=2016NatSR...624874G}}</ref>

Class [[Spirotrich]]ea<br>

| subdivision = *[[Postciliodesmatophora]]

&nbsp;&nbsp;&nbsp; [[Choreotrich]]ia (e.g. ''[[Tintinnidium]]'')<br>

**[[Heterotrich]]ea

&nbsp;&nbsp;&nbsp; [[Oligotrich]]ia (e.g. ''[[Halteria]]'')<br>

**[[Karyorelictea]]

&nbsp;&nbsp;&nbsp; [[Stichotrich]]ia (e.g. ''[[Stylonychia]]'')<br>

*[[Intramacronucleata]]

&nbsp;&nbsp;&nbsp; [[Hypotrich]]ia (e.g. ''[[Euplotes]]'')<br>

**[[Armophorea]]

Class [[Litostomatea]]<br>

**[[Litostomatea]]

&nbsp;&nbsp;&nbsp; [[Haptoria]] (e.g. ''[[Didinium]]'')<br>

**[[Colpodea]]

&nbsp;&nbsp;&nbsp; [[Trichostome|Trichostomatia]] (e.g. ''[[Balantidium]]'')<br>

**[[Nassophorea]]

Class [[Phyllopharyngea]]<br>

**[[Phyllopharyngea]]

&nbsp;&nbsp;&nbsp; [[Phyllopharyngia]]<br>

**[[Prostomatea]]

&nbsp;&nbsp;&nbsp; [[Rhynchodia]]<br>

**[[Plagiopylid|Plagiopylea]]

&nbsp;&nbsp;&nbsp; [[Chonotrich]]ia<br>

**[[Oligohymenophorea]]

&nbsp;&nbsp;&nbsp; [[Suctoria]] (e.g. ''[[Podophrya]]'')<br>

**[[Protocruziea]]

Class [[Nassophorea]]<br>

**[[Spirotrich]]ea

Class [[Colpodea]] (e.g. ''[[Colpoda]]'')<br>

**[[Cariacotrichea]]

Class [[Prostomatea]] (e.g. ''[[Coleps]]'')<br>

**[[Muranotrichea]]

Class [[Oligohymenophorea]]<br>

**[[Parablepharismea]]

&nbsp;&nbsp;&nbsp; [[Peniculid|Peniculia]] (e.g. ''[[Paramecium]]'')<br>

See text for subclasses.

&nbsp;&nbsp;&nbsp; [[Hymenostome|Hymenostomatia]] (e.g. ''[[Tetrahymena]]'')<br>

| synonyms = * Ciliata <small>Perty, 1852</small>

&nbsp;&nbsp;&nbsp; [[Scuticociliate|Scuticociliatia]]<br>

}}

&nbsp;&nbsp;&nbsp; [[Peritrich]]ia (e.g. ''[[Vorticella]]'')<br>

&nbsp;&nbsp;&nbsp; [[Astome|Astromatia]]<br>

&nbsp;&nbsp;&nbsp; [[Apostome|Apostomatia]]<br>

Class [[Plagiopylid|Plagiopylea]]

{{Taxobox_end}}

The '''ciliates''' are one of the most important groups of [[protist]]s, common almost everywhere there is water - [[lake]]s, [[pond]]s, [[ocean]]s, and [[soil]]s, with many [[Ectosymbiosis|ecto]]- and [[endosymbiotic]] members, as well as some obligate and opportunistic parasites. Ciliates tend to be large protozoa, a few reaching 2 mm in length, and are some of the most complex in structure. The name ''ciliate'' comes from the presence of hair-like organelles called [[cilium|cilia]], which are identical in structure to [[flagellum|flagella]] but typically shorter and present in much larger numbers. Cilia occur in all members of the group, although the peculiar [[suctoria]] only have them for part of the life-cycle, and are variously used in swimming, crawling, attachment, feeding, and sensation.

The '''ciliates''' are a group of [[alveolate]]s characterized by the presence of hair-like organelles called [[cilia]], which are identical in structure to [[flagellum|eukaryotic flagella]], but are in general shorter and present in much larger numbers, with a different [[wikt:undulating|undulating]] pattern than flagella. Cilia occur in all members of the group (although the peculiar [[Suctoria]] only have them for part of their [[biological life cycle|life cycle]]) and are variously used in swimming, crawling, attachment, feeding, and sensation.

Unlike other [[eukaryote]]s, ciliates have two different sorts of [[cell nucleus|nuclei]]: a small, [[diploid]] [[micronucleus]] (reproduction), and a large, [[polyploid]] [[macronucleus]] (general cell regulation). The latter is generated from the micronucleus by amplification of the genome and heavy editing. The high degree of polyploidi allows the cell to sustain an appropriate level of [[transcription (genetics)|transcription]]. Division of the macronucleus does not occur by a [[mitosis|mitotic process]] but segregation of the chromosomes is by a different process, whose mechanism is unknown. This process is by no means perfect, and after about 200 generations the cell shows signs of aging. Periodically the macronuclei must be regenerated from the micronuclei. In most, this occurs during [[sexual reproduction]], which is not usually through [[syngamy]] but through ''conjugation''. Here two cells line up, the micronuclei undergo [[meiosis]], some of the [[haploid]] daughters are exchanged and then fuse to form new micro- and macronuclei.

Ciliates are an important group of [[protist]]s, common almost anywhere there is water—in lakes, ponds, oceans, rivers, and soils, including anoxic and oxygen-depleted habitats.<ref>{{cite journal | pmid=35325496 | year=2022 | last1=Rotterová | first1=J. | last2=Edgcomb | first2=V. P. | last3=Čepička | first3=I. | last4=Beinart | first4=R. | title=Anaerobic ciliates as a model group for studying symbioses in oxygen-depleted environments | journal=The Journal of Eukaryotic Microbiology | volume=69 | issue=5 | pages=e12912 | doi=10.1111/jeu.12912 | s2cid=247677842 }}</ref> About 4,500 unique free-living species have been described, and the potential number of extant species is estimated at 27,000–40,000.<ref>{{Cite book|url=https://www.springer.com/gp/book/9789048128006|title=Protist Diversity and Geographical Distribution|date=2009|publisher=Springer Netherlands|isbn=9789048128006|editor-last=Foissner|editor-first=W.|series=Topics in Biodiversity and Conservation|volume=8|pages=111|doi=10.1007/978-90-481-2801-3|language=en|editor-last2=Hawksworth|editor-first2=David}}</ref> Included in this number are many [[Ectosymbiosis|ectosymbiotic]] and [[endosymbiotic]] species, as well as some [[Obligate parasite|obligate]] and [[Facultative parasite|opportunistic]] [[parasite]]s. Ciliate species range in size from as little as 10 [[micrometres|μm]] in some [[colpodea]]ns to as much as 4&nbsp;mm in length in some [[Geleiidae|geleiids]], and include some of the most [[Morphology (biology)|morphologically]] complex protozoans.<ref>{{cite journal | last1 = Nielsen | first1 = Torkel Gissel | last2 = Kiørboe | first2 = Thomas | year = 1994 | title = Regulation of zooplankton biomass and production in a temperate, coastal ecosystem. 2. Ciliates | journal = Limnology and Oceanography | volume = 39 | issue = 3| pages = 508–519 | doi=10.4319/lo.1994.39.3.0508| bibcode = 1994LimOc..39..508N | doi-access = free }}</ref><ref>{{Cite book|title = The Ciliated Protozoa 3rd Edition|url = https://archive.org/details/ciliatedprotozoa00lynn_842|url-access = limited|last = Lynn|first = Denis|publisher = Springer|year = 2008|isbn = 978-1-4020-8238-2|pages = [https://archive.org/details/ciliatedprotozoa00lynn_842/page/n158 129]}}</ref>

With a few exceptions, there is a distinct ''[[cytostome]]'' or mouth where ingestion takes place. Food [[vacuole]]s are formed through [[phagocytosis]] and typically follow a particular path through the cell as their contents are digested and broken down via [[lysosomes]] so the substances the vacuole contains are then small enough to [[diffuse]] through the membrane of the food vacuole into the cell. Anything left in the food vacuole by the time it reaches the cytoproct (anus) is discharged via [[exocytosis]]. Most ciliates also have one or more prominent contractile vacuoles, which collect water through pinocytosis and expel it from the cell to maintain osmotic pressure, or in some function to maintain ionic balance. These often have a distinctive star-shape, with each point being a collecting tube.

In most systems of [[biological classification|taxonomy]], "'''Ciliophora'''" is ranked as a [[phylum]]<ref>{{cite web|title=ITIS Report|url=https://www.itis.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value=46211|website=Integrated Taxonomic Information System|access-date=11 December 2014}}</ref> under any of several [[Kingdom (biology)|kingdoms]], including [[Chromista]],<ref>{{Cite journal|last=Cavalier-Smith|first=Thomas|date=2018-01-01|title=Kingdom Chromista and its eight phyla: a new synthesis emphasising periplastid protein targeting, cytoskeletal and periplastid evolution, and ancient divergences|journal=Protoplasma|language=en|volume=255|issue=1|pages=297–357|doi=10.1007/s00709-017-1147-3|issn=1615-6102|pmc=5756292|pmid=28875267|bibcode=2018Prpls.255..297C }}</ref> [[Protista]]<ref name="pmid19121402">{{cite journal|vauthors=Yi Z, Song W, Clamp JC, Chen Z, Gao S, Zhang Q |title=Reconsideration of systematic relationships within the order Euplotida (Protista, Ciliophora) using new sequences of the gene coding for small-subunit rRNA and testing the use of combined data sets to construct phylogenies of the Diophrys-complex|journal=Mol. Phylogenet. Evol.|volume=50|issue=3|pages=599–607|date=December 2008|pmid=19121402|doi=10.1016/j.ympev.2008.12.006}}</ref> or [[Protozoa]].<ref name="pmid17669163">{{cite journal|vauthors=Miao M, Song W, Chen Z |title=A unique euplotid ciliate, Gastrocirrhus (Protozoa, Ciliophora): assessment of its phylogenetic position inferred from the small subunit rRNA gene sequence|journal=J. Eukaryot. Microbiol.|volume=54|issue=4|pages=371–8|year=2007|pmid=17669163|doi=10.1111/j.1550-7408.2007.00271.x|s2cid=25977768|display-authors=etal}}</ref> In some older systems of classification, such as the influential taxonomic works of [[Alfred Kahl]], ciliated protozoa are placed within the [[Class (biology)|class]] "'''Ciliata'''"<ref>{{Cite book|last=Alfred Kahl|url=https://archive.org/details/1930AlfredKahlVolumeIGeneralSectionAndProstomata|title=Urtiere oder Protozoa I: Wimpertiere oder Ciliata -- Volume I General Section And Prostomata|date=1930}}</ref><ref>{{Cite web|url=https://www.merriam-webster.com/medical/Ciliata|title=Medical Definition of CILIATA|website=www.merriam-webster.com|language=en|access-date=2017-12-22}}</ref> (a term which can also refer to a [[Ciliata (fish)|genus of fish]]). In the taxonomic scheme endorsed by the [[International Society of Protistologists]], which eliminates formal [[Taxonomic rank|rank]] designations such as "phylum" and "class", "Ciliophora" is an unranked [[Taxonomic rank|taxon]] within [[Alveolata]].<ref>{{Cite journal|last1=Adl|first1=Sina M.|last2=Bass|first2=David|last3=Lane|first3=Christopher E.|last4=Lukeš|first4=Julius|last5=Schoch|first5=Conrad L.|last6=Smirnov|first6=Alexey|last7=Agatha|first7=Sabine|last8=Berney|first8=Cedric|last9=Brown|first9=Matthew W.|last10=Burki|first10=Fabien|last11=Cárdenas|first11=Paco|date=2019|title=Revisions to the Classification, Nomenclature, and Diversity of Eukaryotes|journal=Journal of Eukaryotic Microbiology|language=en|volume=66|issue=1|pages=4–119|doi=10.1111/jeu.12691|issn=1550-7408|pmc=6492006|pmid=30257078}}</ref><ref>{{cite journal | last1 = Adl | first1 = Sina M. | display-authors = etal | year = 2005 | title = The new higher level classification of eukaryotes with emphasis on the taxonomy of protists | journal = Journal of Eukaryotic Microbiology | volume = 52 | issue = 5| pages = 399–451 | doi=10.1111/j.1550-7408.2005.00053.x | pmid=16248873| doi-access = free }}</ref>

Most ciliates feed on smaller organisms (heterotrophic), such as [[bacterium|bacteria]] and [[alga]]e, and detritus swept into the mouth by modified oral cilia. These usually include a series of membranelles to the left of the mouth and a paroral membrane to its right, both of which arise from ''polykinetids'', groups of many cilia together with associated structures. This varies considerably, however. Some ciliates are mouthless and feed by absorption, while others are predatory and feed on other protozoa and in particular on other ciliates. This includes the suctoria, which feed through several specialized tentacles.

==Cell structure==

In some forms there are also body polykinetids, for instance, among the [[spirotrich]]s where they generally form bristles called ''cirri''. More often body cilia are arranged in ''mono-'' and ''dikinetids'', which respectively include one and two kinetosomes (basal bodies), each of which may support a cilium. These are arranged into rows called ''kineties'', which run from the anterior to posterior of the cell. The body and oral kinetids make up the ''infraciliature'', an organization unique to the ciliates and important in their classification, and include various fibrils and [[microtubule]]s involved in coordinating the cilia.

===Nuclei===

Unlike most other [[eukaryotes]], ciliates have two different sorts of [[cell nucleus|nuclei]]: a tiny, [[diploid]] [[micronucleus]] (the "generative nucleus", which carries the [[germline]] of the cell), and a large, [[Ploidy|ampliploid]] [[macronucleus]] (the "vegetative nucleus", which takes care of general cell regulation, expressing the [[phenotype]] of the organism).<ref>{{Cite journal|last=Raikov|first=I.B.|date=1969|title=The Macronucleus of Ciliates|url=https://books.google.com/books?id=YBnLBAAAQBAJ&q=raikov+macronucleus&pg=PA1|journal=Research in Protozoology|volume=3|pages=4–115|isbn=9781483186146}}</ref><ref name=":2">{{Cite book|url=https://www.springer.com/gp/book/9783319281476|title=Handbook of the Protists|date=2017|publisher=Springer International Publishing|isbn=978-3-319-28147-6|editor-last=Archibald|editor-first=John M.|edition=2|pages=691|language=en|editor-last2=Simpson|editor-first2=Alastair G. B.|editor-last3=Slamovits|editor-first3=Claudio H.}}</ref> The latter is generated from the micronucleus by amplification of the [[genome]] and heavy editing. The micronucleus passes its genetic material to offspring, but does not express its genes. The macronucleus provides the [[small nuclear RNA]] for vegetative growth.<ref>{{Cite journal|last=Prescott|first=D M|date=June 1994|title=The DNA of ciliated protozoa.|journal=Microbiological Reviews|volume=58|issue=2|pages=233–267|doi=10.1128/mr.58.2.233-267.1994|issn=0146-0749|pmid=8078435|pmc=372963}}</ref><ref name=":2" />

Division of the macronucleus occurs in most ciliate species, apart from those in class Karyorelictea, whose macronuclei are replaced every time the cell divides.<ref name=":3" /> Macronuclear division is accomplished by [[amitosis]], and the segregation of the [[chromosome]]s occurs by a process whose mechanism is unknown.<ref name=":2" /> After a certain number of generations (200–350, in ''Paramecium aurelia'', and as many as 1,500 in ''Tetrahymena<ref name=":3" />'') the cell shows signs of aging, and the macronuclei must be regenerated from the micronuclei. Usually, this occurs following ''[[#Reproduction and sexual phenomena|conjugation]]'', after which a new macronucleus is generated from the post-conjugal micronucleus.<ref name=":2" />

The infraciliature is one of the main component of the cell cortex. Another are the ''alveoli'', small vesicles under the cell membrane that are packed against it to form a [[pellicle]] maintaining the cell's shape, which varies from flexible and contractile to rigid. Numerous [[mitochondrion|mitochondria]] and [[extrusome]]s are also generally present. The presence of alveoli, the structure of the cilia, the form of mitosis and various other details indicate a close relationship between the ciliates, [[Apicomplexa]], and [[dinoflagellate]]s. These superficially dissimilar groups make up the [[alveolate]]s.

[[Category:Protista]][[Category:Ciliates|*]]

[[File:2023 Ciliate.svg|thumb|center|upright=2|{{center|'''Representation of a ciliate'''}} {{ordered list|Cilia|

[[de:Wimpertierchen]]

[[es:CiliophoraTrichocyst]]|

Alveoli, surface cavities or pits|

[[fr:Ciliata]]

[[Contractile vacuole]], regulates the quantity of water inside a cell|

[[nl:Ciliophora]]

Contractile vacuole pore|

[[nds:Ciliophora]]

Radial canal|

[[ja:繊毛虫]]

[[Food vacuole|Food vacuoles]]|

[[pt:Ciliado]]

[[Lysosome]], holds enzymes|

[[sv:Ciliater]]

[[Golgi apparatus]]; modifies [[protein]]s and sends them out of the cell|

[[Micronucleus]]|

[[Macronucleus]], controls non-reproductive cell functions|

Vestibulum|

Buccal cavity|

Quadrulus|

[[Cytostome]], cell mouth|

Nascent food vacuole|

Acidosome, vesicle involved in the acidification of phagocytes|

Waste vacuole|

[[Anal pore|Cytoproct]], anal pore for waste ejection|

[[Endoplasmic reticulum]], the transport network for molecules going to specific parts of the cell|

[[Mitochondria|Mitochondrion]], creates [[Adenosine triphosphate|ATP]] (energy) for the cell (tubularcristae)|

[[Endosymbiont|Endosymbionts]]}}]]

===Cytoplasm===

[[Food vacuole]]s are formed through [[phagocytosis]] and typically follow a particular path through the cell as their contents are digested and broken down by [[lysosomes]] so the substances the [[vacuole]] contains are then small enough to [[Diffusion|diffuse]] through the membrane of the food vacuole into the cell. Anything left in the food vacuole by the time it reaches the cytoproct ([[anal pore]]) is discharged by [[exocytosis]]. Most ciliates also have one or more prominent [[contractile vacuole]]s, which collect water and expel it from the cell to maintain [[osmotic pressure]], or in some function to maintain ionic balance. In some genera, such as ''[[Paramecium]]'', these have a distinctive star shape, with each point being a collecting tube.

===Specialized structures in ciliates===

{{anchor|Specialized_structures_in_ciliates}}

<!-- The "Kinety" page links here -->

Mostly, body cilia are arranged in ''mono-'' and ''[[wikt:dikinetid|dikinetids]]'', which respectively include one and two [[kinetosome]]s (basal bodies), each of which may support a cilium. These are arranged into rows called ''kineties'', which run from the anterior to posterior of the cell. The body and oral kinetids make up the ''infraciliature'', an organization unique to the ciliates and important in their classification, and include various fibrils and [[microtubule]]s involved in coordinating the cilia. In some forms there are also body polykinetids, for instance, among the [[spirotrich]]s where they generally form bristles called [[Cirrus (biology)|cirri]].

The infraciliature is one of the main components of the [[cell cortex]]. Others are the ''alveoli'', small vesicles under the cell membrane that are packed against it to form a [[Protozoa#Walls, pellicles, scales, and skeletons|pellicle]] maintaining the cell's shape, which varies from flexible and contractile to rigid. Numerous [[Mitochondrion|mitochondria]] and [[extrusome]]s are also generally present. The presence of alveoli, the structure of the cilia, the form of mitosis and various other details indicate a close relationship between the ciliates, [[Apicomplexa]], and [[dinoflagellate]]s. These superficially dissimilar groups make up the [[alveolate]]s.

==Feeding==

Most ciliates are [[heterotroph]]s, feeding on smaller organisms, such as [[Bacterium|bacteria]] and [[alga]]e, and detritus swept into the oral groove (mouth) by modified oral cilia. This usually includes a series of [[membranelle]]s to the left of the mouth and a paroral membrane to its right, both of which arise from ''polykinetids'', groups of many cilia together with associated structures. The food is moved by the cilia through the mouth pore into the gullet, which forms food vacuoles.

Many species are also [[mixotroph]]ic, combining [[Phagocytosis|phagotrophy]] and [[phototroph]]y through [[kleptoplasty]] or symbiosis with photosynthetic microbes.<ref>{{cite journal | pmid=20970377 | year=2010 | last1=Esteban | first1=G. F. | last2=Fenchel | first2=T. | last3=Finlay | first3=B. J. | title=Mixotrophy in ciliates | journal=Protist | volume=161 | issue=5 | pages=621–641 | doi=10.1016/j.protis.2010.08.002 }}</ref><ref>{{cite journal | pmid=32917704 | year=2020 | last1=Altenburger | first1=A. | last2=Blossom | first2=H. E. | last3=Garcia-Cuetos | first3=L. | last4=Jakobsen | first4=H. H. | last5=Carstensen | first5=J. | last6=Lundholm | first6=N. | last7=Hansen | first7=P. J. | last8=Haraguchi | first8=L. | last9=Haraguchi | first9=L. | title=Dimorphism in cryptophytes-The case of Teleaulax amphioxeia/Plagioselmis prolonga and its ecological implications | journal=Science Advances | volume=6 | issue=37 | doi=10.1126/sciadv.abb1611 | pmc=7486100 | bibcode=2020SciA....6.1611A }}</ref>

The ciliate ''[[Halteria]]'' has been observed to feed on [[chlorovirus]]es.<ref>{{cite journal|first1=John P.|last1=DeLong|first2=James L.|last2=Van Etten|first3=Zeina|last3=Al-Ameeli|first4=Irina V.|last4=Agarkova|title=The consumption of viruses returns energy to food chains|journal=Proceedings of the National Academy of Sciences|date=2023-01-03|page=e2215000120|volume=120|issue=1|doi=10.1073/pnas.2215000120 |doi-access=free |first5=David D.|last5=Dunigan|pmid=36574690 |pmc=9910503 |bibcode=2023PNAS..12015000D }}</ref>

Feeding techniques vary considerably, however. Some ciliates are mouthless and feed by absorption ([[osmotrophy]]), while others are predatory and feed on other protozoa and in particular on other ciliates. Some ciliates parasitize [[animal]]s, although only one species, ''[[Balantidium coli]]'', is known to cause disease in humans.<ref name="Lynn2008">{{cite book|title=The Ciliated Protozoa: Characterization, Classification, and Guide to the Literature|url=https://archive.org/details/ciliatedprotozoa00lynn_842|url-access=limited|publisher=Springer|year=2008|isbn=978-1-4020-8238-2|edition=3|pages=[https://archive.org/details/ciliatedprotozoa00lynn_842/page/n88 58]|quote=1007/978-1-4020-8239-9|last1=Lynn|first1=Denis}}</ref>

==Reproduction and sexual phenomena==

[[File:Some types of ciliate fission.svg|thumb|450x450px|Most ciliates divide transversally, but other kinds of binary fission occur in some species.]]

=== Reproduction ===

Ciliates reproduce [[Asexual reproduction|asexually]], by various kinds of [[fission (biology)|fission]].<ref name=":3">{{Cite book|last=H.|first=Lynn, Denis|title=The ciliated protozoa: characterization, classification, and guide to the literature|date=2008|publisher=Springer|isbn=9781402082382|___location=New York|pages=324|oclc=272311632}}</ref> During fission, the micronucleus undergoes [[mitosis]] and the macronucleus elongates and undergoes [[amitosis]] (except among the [[Karyorelictea]]n ciliates, whose macronuclei do not divide). The cell then divides in two, and each new cell obtains a copy of the micronucleus and the macronucleus.

[[File:Unk.cilliate.jpg|thumb|Ciliate undergoing the last processes of binary fission]]

[[File:Деления инфузорий Colpidium.webm|thumb| Division of ciliate ''[[Colpidium]]'']]

Typically, the cell is divided transversally, with the [[anterior]] half of the ciliate (the ''proter'') forming one new organism, and the [[posterior (anatomy)|posterior]] half (the ''opisthe'') forming another. However, other types of fission occur in some ciliate groups. These include ''[[budding]]'' (the emergence of small ciliated offspring, or "swarmers", from the body of a mature parent); ''[[strobilation]]'' (multiple divisions along the cell body, producing a chain of new organisms); and ''palintomy'' (multiple fissions, usually within a [[Microbial cyst|cyst]]).<ref name=":0">{{Cite book|title=The ciliated protozoa: characterization, classification, and guide to the literature|last=H.|first=Lynn, Denis|date=2008|publisher=Springer|isbn=9781402082382|___location=New York|pages=23|oclc=272311632}}</ref>

Fission may occur spontaneously, as part of the vegetative [[cell cycle]]. Alternatively, it may proceed as a result of self-fertilization ([[autogamy]]),<ref>{{cite journal |author=Berger JD |title=Autogamy in Paramecium. Cell cycle stage-specific commitment to meiosis |journal=Exp. Cell Res. |volume=166 |issue=2 |pages=475–85 |date=October 1986 |pmid=3743667 |doi=10.1016/0014-4827(86)90492-1 }}</ref> or it may follow [[sexual conjugation|conjugation]], a sexual phenomenon in which ciliates of compatible [[mating type]]s exchange genetic material. While conjugation is sometimes described as a form of reproduction, it is not directly connected with reproductive processes, and does not directly result in an increase in the number of individual ciliates or their progeny.<ref name=":1">{{Cite journal|last=Raikov|first=I.B|date=1972|title=Nuclear phenomena during conjugation and autogamy in ciliates|url=http://www.sciencedirect.com/science/book/9780080164373|journal=Research in Protozoology|volume=4|pages=149}}</ref>

===Conjugation===

;Overview

Ciliate conjugation is a sexual phenomenon that results in [[genetic recombination]] and nuclear reorganization within the cell.<ref name=":1" /><ref name=":0" /> During conjugation, two ciliates of a compatible mating type form a bridge between their [[cytoplasm]]s. The micronuclei undergo [[meiosis]], the macronuclei disappear, and [[haploid]] micronuclei are exchanged over the bridge. In some ciliates (peritrichs, [[chonotrich]]s and some [[suctoria]]ns), conjugating cells become permanently fused, and one conjugant is absorbed by the other.<ref name="Lynn2008" /><ref>Finley, Harold E. "The conjugation of ''Vorticella microstoma''." Transactions of the American Microscopical Society (1943): 97-121.</ref> In most ciliate groups, however, the cells separate after conjugation, and both form new macronuclei from their micronuclei.<ref name="urlIntroduction to the Ciliata">{{cite web|url=http://www.ucmp.berkeley.edu/protista/ciliata.html|title=Introduction to the Ciliata|access-date=2009-01-16}}</ref> Conjugation and autogamy are always followed by fission.<ref name=":0" />

In many ciliates, such as ''Paramecium'', conjugating partners (gamonts) are similar or indistinguishable in size and shape. This is referred to as "isogamontic" conjugation. In some groups, partners are different in size and shape. This is referred to as "anisogamontic" conjugation. In [[Sessilida|sessile peritrichs]], for instance, one sexual partner (the microconjugant) is small and mobile, while the other (macroconjugant) is large and [[Sessility (motility)|sessile]].<ref name=":1" />

;Stages of conjugation[[File:Stages of ciliate conjugation.svg|thumb|562x562px|Stages of conjugation in ''Paramecium caudatum'']]

In ''[[Paramecium caudatum]]'', the stages of conjugation are as follows (see diagram at right):

# Compatible mating strains meet and partly fuse

# The micronuclei undergo meiosis, producing four haploid micronuclei per cell.

# Three of these micronuclei disintegrate. The fourth undergoes mitosis.

# The two cells exchange a micronucleus.

# The cells then separate.

# The micronuclei in each cell fuse, forming a diploid micronucleus.

# Mitosis occurs three times, giving rise to eight micronuclei.

# Four of the new micronuclei transform into macronuclei, and the old macronucleus disintegrates.

# Binary fission occurs twice, yielding four identical daughter cells.

==DNA rearrangements (gene scrambling)==

Ciliates contain two types of nuclei: [[Somatic (biology)|somatic]] "[[macronucleus]]" and the [[germline]] "[[micronucleus]]". Only the DNA in the micronucleus is passed on during sexual reproduction (conjugation). On the other hand, only the DNA in the macronucleus is actively expressed and results in the phenotype of the organism. Macronuclear DNA is derived from micronuclear DNA by extensive DNA rearrangement and amplification.[[File:Development of the Oxytricha macronuclear genome.jpg|thumb |451x451px|Development of the ''[[Oxytricha trifallax|Oxytricha]]'' macronuclear genome from micronuclear genome|left]]

The macronucleus begins as a copy of the micronucleus. The micronuclear chromosomes are fragmented into many smaller pieces and amplified to give many copies. The resulting macronuclear chromosomes often contain only a single [[gene]]. In ''[[Tetrahymena]]'', the micronucleus has 10 chromosomes (five per haploid genome), while the macronucleus has over 20,000 chromosomes.<ref name="pmid21956937">{{cite journal|author=Mochizuki, Kazufumi|title=DNA rearrangements directed by non-coding RNAs in ciliates|journal=Wiley Interdisciplinary Reviews: RNA|volume=1|issue=3|pages=376–387|year=2010|pmid=21956937|doi=10.1002/wrna.34|pmc=3746294}}</ref>

In addition, the micronuclear genes are interrupted by numerous "internal eliminated sequences" (IESs). During development of the macronucleus, IESs are deleted and the remaining gene segments, macronuclear destined sequences (MDSs), are spliced together to give the operational gene. ''Tetrahymena'' has about 6,000 IESs and about 15% of micronuclear DNA is eliminated during this process. The process is guided by [[small RNA]]s and [[epigenetic]] [[chromatin]] marks.<ref name="pmid21956937" />

In [[spirotrich]] ciliates (such as ''[[Oxytricha trifallax|Oxytricha]]''), the process is even more complex due to "gene scrambling": the MDSs in the micronucleus are often in different order and orientation from that in the macronuclear gene, and so in addition to deletion, DNA [[Chromosomal inversion|inversion]] and [[Chromosomal translocation|translocation]] are required for "unscrambling". This process is guided by long RNAs derived from the parental macronucleus. More than 95% of micronuclear DNA is eliminated during spirotrich macronuclear development.<ref name="pmid21956937" />

==Aging==

ln clonal populations of ''Paramecium'', aging occurs over successive generations leading to a gradual loss of vitality, unless the cell line is revitalized by conjugation or [[autogamy]]. In ''Paramecium tetraurelia'', the clonally aging line loses vitality and expires after about 200 fissions, if the cell line is not rejuvenated by conjugation or self-fertilization. The basis for clonal aging was clarified by the [[Transplantation chimera|transplantation]] experiments of Aufderheide in 1986<ref>{{cite journal|last=Aufderheide|first=Karl J.|year=1986|title=Clonal aging in ''Paramecium tetraurelia''. II. Evidence of functional changes in the macronucleus with age|journal=Mechanisms of Ageing and Development|volume=37|issue=3|pages=265–279|doi=10.1016/0047-6374(86)90044-8|pmid=3553762|s2cid=28320562}}</ref> who demonstrated that the macronucleus, rather than the cytoplasm, is responsible for clonal aging. Additional experiments by Smith-Sonneborn,<ref>{{cite journal|last=Smith-Sonneborn|first=J.|year=1979|title=DNA repair and longevity assurance in Paramecium tetraurelia|journal=[[Science (journal)|Science]]|volume=203|issue=4385|pages=1115–1117|doi=10.1126/science.424739|pmid=424739|bibcode=1979Sci...203.1115S}}</ref> Holmes and Holmes,<ref>{{cite journal|last1=Holmes|first1=George E.|last2=Holmes|first2=Norreen R.|title=Accumulation of DNA damages in aging ''Paramecium tetraurelia''|journal=Molecular and General Genetics|date=July 1986|volume=204|issue=1|pages=108–114|doi=10.1007/bf00330196|pmid=3091993|s2cid=11992591}}</ref> and Gilley and Blackburn<ref>{{cite journal|last1=Gilley|first1=David|last2=Blackburn|first2=Elizabeth H.|year=1994|title=Lack of telomere shortening during senescence in ''Paramecium''|url=http://www.pnas.org/content/pnas/91/5/1955.full.pdf|journal=[[Proceedings of the National Academy of Sciences of the United States of America]]|volume=91|issue=5|pages=1955–1958|doi=10.1073/pnas.91.5.1955|pmc=43283|pmid=8127914|bibcode=1994PNAS...91.1955G|doi-access=free}}</ref> demonstrated that, during clonal aging, [[DNA damage]] increases dramatically. Thus, DNA damage appears to be the cause of aging in ''P. tetraurelia''.

== Fossil record ==

Until recently, the oldest ciliate fossils known were [[tintinnid]]s from the [[Ordovician Period|Ordovician period]]. In 2007, Li ''et al.'' published a description of fossil ciliates from the [[Doushantuo Formation]], about 580 million years ago, in the [[Ediacaran|Ediacaran period]]. These included two types of tintinnids and a possible ancestral suctorian.<ref>

{{cite journal|first=C.-W.|last=Li|title=Ciliated protozoans from the Precambrian Doushantuo Formation, Wengan, South China|journal=Geological Society, London, Special Publications|year=2007|volume=286|issue=1|pages=151–156|doi=10.1144/SP286.11|display-authors=etal|bibcode=2007GSLSP.286..151L|s2cid=129584945}}</ref> A fossil ''[[Vorticella]]'' has been discovered inside a leech cocoon from the [[Triassic|Triassic period]], about 200 million years ago.<ref>{{Cite journal|last1=Bomfleur|first1=Benjamin|last2=Kerp|first2=Hans|last3=Taylor|first3=Thomas N.|last4=Moestrup|first4=Øjvind|last5=Taylor|first5=Edith L.|date=2012-12-18|title=Triassic leech cocoon from Antarctica contains fossil bell animal|journal=Proceedings of the National Academy of Sciences of the United States of America|volume=109|issue=51|pages=20971–20974|doi=10.1073/pnas.1218879109|issn=1091-6490|pmc=3529092|pmid=23213234|bibcode=2012PNAS..10920971B|doi-access=free}}</ref>

==Phylogeny==

According to the 2016 phylogenetic analysis,<ref name=Gao2016/> [[Mesodiniea]] is consistently found as the sister group to all other ciliates. Additionally, two big sub-groups are distinguished inside subphylum [[Intramacronucleata]]: SAL ([[Spirotrichea]]+[[Armophorea]]+[[Litostomatea]]) and [[CONthreeP]] or [[Ventrata]] ([[Colpodea]]+[[Oligohymenophorea]]+[[Nassophorea]]+[[Phyllopharyngea]]+[[Plagiopylea]]+[[Prostomatea]]).<ref name=Gao2016/> The class [[Protocruziea]] is found as the sister group to [[Ventrata]]/[[CONthreeP]]. The class [[Cariacotrichea]] was excluded from the analysis, but it was originally established as part of [[Intramacronucleata]]<ref name=Gao2016/>.<br />The [[Odontostomatida|odontostomatids]] were identified in 2018<ref name=Fernandes2018>{{citation|title=Molecular phylogeny and comparative morphology indicate that odontostomatids (Alveolata, Ciliophora) form a distinct class-level taxon related to Armophorea|doi=10.1016/j.ympev.2018.04.026|date=2018|volume=126|pages=382–389|first1=Noemi M. |last1=Fernandes |first2=Vinicius F. |last2=Vizzoni |first3=Bárbara do N. |last3=Borges |first4=Carlos A.G. |last4=Soares|first5=Inácio D. |last5=da Silva-Neto|first6=Thiago da S. |last6=Paiva|journal=Molecular Phylogenetics and Evolution|pmid=29679715 |bibcode=2018MolPE.126..382F |s2cid=5032558 |issn=1055-7903|url=https://www.sciencedirect.com/science/article/pii/S1055790317307273|url-access=subscription}}</ref> as its own class [[Odontostomatida|Odontostomatea]], related to [[Armophorea]].

{{clade|label1='''Ciliophora'''|1={{clade

|1=[[Mesodiniea]]|2={{clade

|label1=[[Postciliodesmatophora]]|1={{clade

|1=[[Karyorelictea]]

|2=[[Heterotrichea]]

}}

|label2=[[Intramacronucleata]]|2={{clade

|label1=SAL|1={{clade

|1=[[Odontostomatida|Odontostomatea]]

|2=[[Armophorea]]

|3=[[Litostomatea]]

|4=[[Spirotrichea]]

}}

|2=[[Cariacotrichea]]|state2=dashed

|3={{clade

|1=[[Protocruziea]]

|label2=[[Ventrata|CONthreeP]]|2={{clade|1=[[Discotrichida]]|2={{clade

|1=[[Colpodea]]

|2={{clade

|1={{clade

|1=[[Nassophorea]]

|2=[[Phyllopharyngea]]

}}

|2={{clade

|1=[[Oligohymenophorea]]

|2={{clade

|1=[[Prostomatea]]

|2=[[Plagiopylea]]

}}

}}}}

}}

}}

}}

}}

}}

}}

}}

== Classification ==

{{Further|Wikispecies:Ciliophora}}

[[File:Stentor roeseli composite image.jpg|thumb|''[[Stentor roeselii]]'']]

Several different classification schemes have been proposed for the ciliates. The following scheme is based on a molecular [[phylogenetic analysis]] of up to four genes from 152 species representing 110 families:<ref name=Gao2016/>

* Class [[Mesodiniea]] (e.g. ''[[Mesodinium]]'')

=== Subphylum Postciliodesmatophora ===

* Class [[Heterotrich]]ea (e.g. ''[[Stentor (genus)|Stentor]]'')

* Class [[Karyorelictea]]

=== Subphylum Intramacronucleata ===

[[File:Oxytricha trifallax.jpg|thumb|''[[Oxytricha trifallax]]'']]

* Class [[Armophorea]]

* Class [[Odontostomatida|Odontostomatea]]<ref name=Fernandes2018/> (e.g. ''[[Discomorphella]]'', ''[[Saprodinium]]'')

* Class [[Cariacotrichea]] (only one species, ''[[Cariacothrix caudata]]'')

* Class [[Muranotrichea]]

* Class [[Parablepharismea]]

* Class [[Colpodea]] (e.g. ''[[Colpoda]]'')

* Class [[Litostomatea]]

** Subclass [[Haptoria]] (e.g. ''[[Didinium]]'')

** Subclass [[Rhynchostomatia]]

** Subclass [[Trichostome|Trichostomatia]] (e.g. ''[[Balantidium]]'')

* Class [[Nassophorea]]

* Class [[Phyllopharyngea]]

** Subclass [[Chonotrichia]]

** Subclass [[Cyrtophoria]]

** Subclass [[Rhynchodia]]

** Subclass [[Suctoria]] (e.g. ''[[Podophyra]]'')

** Subclass [[Synhymenia]]

* Class [[Oligohymenophorea]]

** Subclass [[Apostome|Apostomatia]]

** Subclass [[Astome|Astomatia]]

** Subclass [[Hymenostome|Hymenostomatia]] (e.g. ''[[Tetrahymena]]'')

** Subclass [[Peniculid|Peniculia]] (e.g. ''[[Paramecium]]'')

** Subclass [[Peritrich]]ia (e.g. ''[[Vorticella]]'')

** Subclass [[Scuticociliate|Scuticociliatia]]

* Class [[Plagiopylid|Plagiopylea]]

* Class [[Prostomatea]] (e.g. ''[[Coleps]]'')

* Class [[Protocruziea]]

* Class [[Spirotrichea]]

**Subclass [[Choreotrichia]]

**Subclass [[Euplotia]]

**Subclass [[Hypotrichia]]

**Subclass [[Licnophoria]]

**Subclass [[Oligotrichia]]

**Subclass [[Phacodiniidea]]

**Subclass [[Protohypotrichia]]

=== Other ===

Some old classifications included [[Opalinidae]] in the ciliates. The fundamental difference between multiciliate [[flagellates]] (e.g., [[hemimastigid]]s, ''[[Stephanopogon]]'', ''[[Multicilia]]'', [[Opalinidae|opalines]]) and ciliates is the presence of macronuclei in ciliates alone.<ref>Cavalier-Smith, T. (2000). Flagellate megaevolution: the basis for eukaryote diversification. In: Leadbeater, B.S.C., Green, J.C. (eds.). ''The Flagellates. Unity, diversity and evolution''. London: Taylor and Francis, pp. 361-390, p. 362, [https://books.google.com/books?id=TMpJo2rXAT4C&pg=PA362].</ref>

== Pathogenicity ==

The only member of the ciliate phylum known to be [[pathogen]]ic to humans is ''[[Balantidium coli]]'',<ref>{{cite web |title=Balantidiasis |date=2013 |work=DPDx — Laboratory Identification of Parasitic Diseases of Public Health Concern |publisher=Centers for Disease Control and Prevention |url=https://www.cdc.gov/dpdx/balantidiasis/index.html |ref={{harvid|DPDx Balantidiasis}}}}</ref> which causes the disease [[balantidiasis]]. It is not pathogenic to the domestic pig, the primary reservoir of this pathogen.<ref>{{Cite journal|author=Schister, Frederick L. and Lynn Ramirez-Avila |title=Current World Status of ''Balantidium coli'' |journal=Clinical Microbiology Reviews |volume=21 |issue=4 |pages=626–638 |date=October 2008 |pmid=18854484 |doi=10.1128/CMR.00021-08 |pmc=2570149}}</ref>

== References ==

{{Reflist|2}}

== Further reading ==

* {{Cite book|title=The ciliated protozoa: characterization, classification, and guide to the literature|last=Lynn|first=Denis H.|date=2008|publisher=Springer|isbn=9781402082382|___location=New York|oclc=272311632}}

* {{Cite book|title=Ciliates: cells as organisms|date=1996|publisher=Gustav Fischer Verlag |editor=Hausmann, Klaus |editor2=Bradbury, Phyllis C. |isbn=978-3437250361|___location=Stuttgart|oclc=34782787}}

* {{Cite book|title=An illustrated guide to the protozoa: organisms traditionally referred to as protozoa, or newly discovered groups|date=2000|publisher=Society of Protozoologists|editor=Lee, John J. |editor2=Leedale, Gordon F. |editor3=Bradbury, Phyllis C. |isbn=9781891276224|edition=2nd|___location=Lawrence, KS |oclc=49191284}}

== External links ==

* {{Commons category-inline|Ciliophora}}

{{Life on Earth}}

{{Eukaryota|D.}}

{{Alveolata}}

{{Protozoa protist}}

{{Taxonbar|from=Q106345}}

{{Authority control}}

[[Category:Ciliates| ]]