View source for Alveolate

{{Short description|Superphylum of protists}}
{{Cs1 config|name-list-style=vanc}}
{{Automatic taxobox
 | fossil_range = {{fossil range|Ediacaran|present|[[Ediacaran]]–[[Holocene|Recent]]|refs=<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=151–6
 | doi = 10.1144/SP286.11
 | bibcode = 2007GSLSP.286..151L
 | s2cid = 129584945
 |display-authors=etal}}
</ref>}}
| image = Ceratium furca.jpg
| image_caption = ''[[Ceratium furca]]''
| display_parents = 5
| taxon = Alveolata
| authority = [[Thomas Cavalier-Smith|Cavalier-Smith]], 1991
| subdivision_ranks = Phyla
| subdivision = 
* [[Ciliophora]]
* [[Myzozoa]]
| synonyms =
* Alveolatobiontes
}}

The '''alveolates''' (meaning "pitted like a honeycomb")<ref>{{cite web |url=http://www.memidex.com/alveolate |title=alveolate |work=Memidex (WordNet) Dictionary/Thesaurus |access-date=2011-01-26 |archive-url=https://web.archive.org/web/20160411233722/http://www.memidex.com/alveolate |archive-date=2016-04-11 |url-status=dead }}</ref> are a group of [[protist]]s, considered a major [[clade]]<ref name="Adl2012">{{cite journal | last1 = Adl | first1 = S.M. | display-authors = etal   | year = 2012 | title = The revised classification of eukaryotes | journal = Journal of Eukaryotic Microbiology | volume = 59 | issue = 5| pages = 429–514 | doi=10.1111/j.1550-7408.2012.00644.x | pmid=23020233 | pmc=3483872}}</ref> and [[Biological classification|superphylum]]<ref name=Ruggiero15>{{cite journal |vauthors=Ruggiero MA, Gordon DP, Orrell TM, Bailly N, Bourgoin T, Brusca RC, Cavalier-Smith T, Guiry MD, Kirk PM |title=A higher level classification of all living organisms |journal=PLOS ONE |volume=10 |issue=4 |pages=e0119248 |year=2015 |pmid=25923521 |pmc=4418965 |doi=10.1371/journal.pone.0119248 |bibcode=2015PLoSO..1019248R |doi-access=free }}</ref> within [[Eukarya]]. They are currently grouped with the [[stramenopile]]s and [[Rhizaria]] among the protists with tubulocristate mitochondria into the [[SAR supergroup]].

==Characteristics==
The most notable shared characteristic is the presence of [[cortical alveolum|cortical (near the surface) alveoli (sacs)]]. These are flattened [[vesicle (biology)|vesicle]]s (sacs) arranged as a layer just under the [[cell membrane|membrane]] and supporting it, typically contributing to a flexible pellicle (thin skin). In armored [[dinoflagellates]] they may contain stiff plates. Alveolates have [[mitochondrion|mitochondria]] with tubular cristae ([[invaginations]]), and cells often have pore-like intrusions through the cell surface. The group contains free-living and [[parasitic]] organisms, predatory [[flagellates]], and [[photosynthetic]] organisms.

[[File:EM alveoli ciliate paramecium putrinum.jpg|600px|thumb|center|Transmission electron micrograph of a thin section of the surface of the ciliate ''[[Paramecium]] putrinum'', showing the alveoli (red arrows) under the cell surface]]

Almost all sequenced mitochondrial genomes of ciliates and apicomplexa are linear.<ref name="Barth2011">{{Cite journal |last1=Barth |first1=D |last2=Berendonk |first2=TU |year=2011 |title=The mitochondrial genome sequence of the ciliate ''Paramecium caudatum'' reveals a shift in nucleotide composition and codon usage within the genus ''Paramecium'' |journal=BMC Genomics |volume=12 |page=272 |doi=10.1186/1471-2164-12-272 |pmc=3118789 |pmid=21627782 |doi-access=free}}</ref> The mitochondria almost all carry [[mtDNA]] of their own but with greatly reduced genome sizes. Exceptions are ''[[Cryptosporidium]]'' which are left with only a [[mitosome]], the circular mitochondrial genomes of ''[[Acavomonas]]'' and ''[[Babesia microti]]'',<ref name="Obornik-Lukes-2015">{{Cite journal |last1=Oborník |first1=Miroslav |last2=Lukeš |first2=Julius |date=2015-10-15 |title=The Organellar Genomes of Chromera and Vitrella, the Phototrophic Relatives of Apicomplexan Parasites |url=https://www.annualreviews.org/content/journals/10.1146/annurev-micro-091014-104449 |journal=Annual Review of Microbiology |volume=69 |pages=129–144 |doi=10.1146/annurev-micro-091014-104449 |issn=0066-4227 |pmid=26092225 |access-date=2024-04-15}}</ref><ref name="Cornillot2012">{{Cite journal |vauthors=Cornillot E, Hadj-Kaddour K, Dassouli A, Noel B, Ranwez V, Vacherie B, Augagneur Y, Brès V, Duclos A, Randazzo S, Carcy B, Debierre-Grockiego F, Delbecq S, Moubri-Ménage K, Shams-Eldin H, Usmani-Brown S, Bringaud F, Wincker P, Vivarès CP, Schwarz RT, Schetters TP, Krause PJ, Gorenflot A, Berry V, Barbe V, Ben Mamoun C |year=2012 |title=Sequencing of the smallest Apicomplexan genome from the human pathogen ''Babesia microti'' |journal=Nucleic Acids Res. |volume=40 |issue=18 |pages=9102–14 |doi=10.1093/nar/gks700 |pmc=3467087 |pmid=22833609}}</ref> and ''[[Toxoplasma]]'''s highly fragmented mitochondrial genome, consisting of 21 sequence blocks which recombine to produce longer segments.<ref>{{Cite journal |last1=Namasivayam |first1=Sivaranjani |last2=Baptista |first2=Rodrigo P. |last3=Xiao |first3=Wenyuan |last4=Hall |first4=Erica M. |last5=Doggett |first5=Joseph S. |last6=Troell |first6=Karin |last7=Kissinger |first7=Jessica C. |date=May 2021 |title=A novel fragmented mitochondrial genome in the protist pathogen Toxoplasma gondii and related tissue coccidia |journal=Genome Research |volume=31 |issue=5 |pages=852–865 |doi=10.1101/gr.266403.120 |pmc=8092004 |pmid=33906963}}</ref><ref>{{Cite journal |last1=Namasivayam |first1=Sivaranjani |last2=Sun |first2=Cheng |last3=Bah |first3=Assiatu B. |last4=Oberstaller |first4=Jenna |last5=Pierre-Louis |first5=Edwin |last6=Etheridge |first6=Ronald Drew |last7=Feschotte |first7=Cedric |last8=Pritham |first8=Ellen J. |last9=Kissinger |first9=Jessica C. |date=2023-11-07 |title=Massive invasion of organellar DNA drives nuclear genome evolution in Toxoplasma |journal=Proceedings of the National Academy of Sciences |volume=120 |issue=45 |pages=–2308569120 |bibcode=2023PNAS..12008569N |doi=10.1073/pnas.2308569120 |pmc=10636329 |pmid=37917792 }}</ref>

==History==
The relationship of apicomplexa, dinoflagellates and ciliates had been suggested during the 1980s, and this was confirmed in the early 1990s by comparisons of ribosomal RNA sequences, most notably by Gajadhar ''et al''.<ref>
{{cite journal | author = Gajadhar, A. A.
| title = Ribosomal RNA sequences of ''Sarcocystis muris'', ''Theilera annulata'', and ''Crypthecodinium cohnii'' reveal evolutionary relationships among apicomplexans, dinoflagellates, and ciliates
| journal = Molecular and Biochemical Parasitology
| year = 1991 | volume = 45 | issue = 1
| pages = 147–153 | doi = 10.1016/0166-6851(91)90036-6
| pmid = 1904987
|display-authors=etal}}.  
</ref> [[Thomas Cavalier-Smith|Cavalier-Smith]] introduced the formal name Alveolata in 1991,<ref name="Cavalier-Smith, T. 1991 pp. 113-131">{{cite book |last=Cavalier-Smith |first=T. |chapter=Cell diversification in heterotrophic flagellates |pages=113–131 |editor-first=David J. |editor-last=Patterson |editor2-first=Jacob |editor2-last=Larsen |editor3=Systematics Association |title=The Biology of free-living heterotrophic flagellates |chapter-url=https://books.google.com/books?id=-JUWAQAAIAAJ |year=1991 |publisher=Oxford University Press |isbn=978-0-19-857747-8}}</ref> although at the time he considered the grouping to be a [[paraphyletic]] assemblage. Many biologists prefer the use of the colloquial name 'alveolate'.<ref>Kumar, S. & Rzhetsky, A. 1996. Evolutionary relationships of eukaryotic kingdoms. Journal of Molecular Evolution, 42: 183–193</ref>

==Classification==
Alveolata include around nine major and minor groups. They are diverse in form, and are known to be related by various ultrastructural and genetic similarities:<ref name=Tikhonenkov14>{{cite journal | doi = 10.1371/journal.pone.0095467 | pmid=24740116 | pmc=3989336 | volume=9 | issue=4 | title=Description of ''Colponema vietnamica'' sp.n. and ''Acavomonas peruviana'' n. gen. n. sp., two new alveolate phyla (Colponemidia nom. nov. and Acavomonidia nom. nov.) and their contributions to reconstructing the ancestral state of alveolates and eukaryotes | year=2014 | journal=PLOS ONE | pages=e95467 | last1 = Tikhonenkov | first1 = DV | last2 = Janouškovec | first2 = J | last3 = Mylnikov | first3 = AP | last4 = Mikhailov | first4 = KV | last5 = Simdyanov | first5 = TG | last6 = Aleoshin | first6 = VV | last7 = Keeling | first7 = PJ| bibcode=2014PLoSO...995467T | doi-access=free }}</ref>

*[[Ciliate]]s – very common protozoa with many short [[cilium|cilia]] arranged in rows, and two nuclei
*[[Acavomonidia]]<ref name=Tikhonenkov14/>
*[[Colponemidia]]<ref name=Tikhonenkov14/>
*[[Dinoflagellate]]s s.l. – mostly marine [[flagellate]]s many of which have [[chloroplast]]s
*[[Perkinsozoa]]
*[[Chromerida]] – a marine phylum of photosynthetic protozoa
*[[Colpodellida]]
*[[Voromonadida]]
*[[Sporozoa|Apicomplexa]] – parasitic and secondary non-photosynthetic protozoa that lack [[Axoneme|axonemal]] locomotive structures except in [[gamete]]s

The Acavomonidia and Colponemidia were previously grouped together as colponemids, a taxon now split because each has a distinctive organization or [[ultrastructural identity]]. The Acavomonidia are closer to the dinoflagellate/perkinsid group than the Colponemidia are.<ref name=Tikhonenkov14/> As such, the informal term "colponemids", as it stands currently, covers two non-sister groups within Alveolata: the Acavomonidia and the Colponemidia.<ref name=Tikhonenkov14/>

The Apicomplexa and dinoflagellates may be more closely related to each other than to the ciliates.  Both have [[plastid]]s, and most share a bundle or cone of [[microtubule]]s at the top of the cell.  In apicomplexans this forms part of a complex used to enter host cells, while in some colorless dinoflagellates it forms a peduncle used to ingest prey.  Various other genera are closely related to these two groups, mostly flagellates with a similar apical structure.  These include free-living members in ''[[Oxyrrhis]]'' and ''[[Colponema]]'', and parasites in ''[[Perkinsus marinus|Perkinsus]]'',<ref name=Zhang2011>{{cite journal | last1 = Zhang | first1 = H | last2 = Campbell | first2 = DA | last3 = Sturm | first3 = NR | last4 = Dungan | first4 = CF | last5 = Lin | first5 = S | year = 2011 | title = Spliced leader RNAs, mitochondrial gene frameshifts and multi-protein phylogeny expand support for the genus ''Perkinsus'' as a unique group of Alveolates | journal = PLOS ONE | volume = 6 | issue = 5| page = e19933 | doi=10.1371/journal.pone.0019933 | pmid=21629701 | pmc=3101222| bibcode = 2011PLoSO...619933Z | doi-access = free }}</ref> ''[[Parvilucifera]]'', ''[[Rastrimonas]]'' and the [[ellobiopsid]]s.  In 2001, direct amplification of the [[rRNA]] gene in marine [[picoplankton]] samples revealed the presence of two novel alveolate lineages, called group I and II.<ref>{{cite journal |vauthors=López-García P, Rodríguez-Valera F, Pedrós-Alió C, Moreira D |title=Unexpected diversity of small eukaryotes in deep-sea Antarctic plankton |journal=Nature |volume=409 |issue=6820 |pages=603–7 |year=2001 |pmid=11214316 |doi=10.1038/35054537 |bibcode=2001Natur.409..603L |s2cid=11550698 }}</ref><ref>{{cite journal |vauthors=Moon-van der Staay SY, De Wachter R, Vaulot D |title=Oceanic 18S rDNA sequences from picoplankton reveal unsuspected eukaryotic diversity |journal=Nature |volume=409 |issue=6820 |pages=607–10 |year=2001 |pmid=11214317 |doi=10.1038/35054541 |bibcode=2001Natur.409..607M |s2cid=4362835 }}</ref>  Group I has no cultivated relatives, while group II is related to the dinoflagellate parasite ''[[Amoebophrya]]'', which was classified until now in the [[Syndiniales]] dinoflagellate order.

Some studies suggested the [[Ascetosporea|haplosporid]]s, mostly parasites of marine invertebrates, might belong here, but they lack alveoli and are now placed among the [[Cercozoa]].

The ellobiopsids are of uncertain relation within the alveolates. Silberman et al 2004 establish that the ''[[Thalassomyces]]'' genus of ellobiopsids are alveolates using [[phylogenetic]] analysis, however {{as of|2016|lc=yes}} no more certainty exists on their place.<ref name="Hoppenrath-2016">{{cite journal | last=Hoppenrath | first=Mona | title=Dinoflagellate taxonomy — a review and proposal of a revised classification | journal=[[Marine Biodiversity]] | publisher=[[Senckenberg Institute]] ([[Springer Science+Business Media|Springer]]) | volume=47 | issue=2 | date=2016-04-29 | issn=1867-1616 | doi=10.1007/s12526-016-0471-8 | pages=381–403| s2cid=42100119 }}</ref><ref name="Taylor-2004">{{cite journal | last=Taylor | first=F. J. R. "Max" | title=Illumination or confusion? Dinoflagellate molecular phylogenetic data viewed from a primarily morphological standpoint | journal=[[Phycological Research]] | publisher=[[Japanese Society of Phycology]] ([[Wiley Publishing|Wiley]]) | volume=52 | issue=4 | year=2004 | issn=1322-0829 | doi=10.1111/j.1440-183.2004.00360.x | pages=308–324| s2cid=86797666 }}</ref>

===Phylogeny===

In 2017, [[Thomas Cavalier-Smith]] described the phylogeny of the Alveolata as follows:<ref name="Cavalier-Smith 2017">{{Cite journal |last=Cavalier-Smith |first=Thomas |date=5 September 2017 |title=Kingdom Chromista and its eight phyla: a new synthesis emphasising periplastid protein targeting, cytoskeletal and periplastid evolution, and ancient divergences |journal=Protoplasma |pages=297–357 |doi=10.1007/s00709-017-1147-3 |pmid=28875267 |pmc=5756292 |volume=255 |issue=1}}</ref>

{{clade| style=font-size:100%;line-height:100%
|label1=[[Alveolata]]
|1={{clade
  |label1=[[Ciliophora]]
  |1={{clade
    |label1=[[Intramacronucleata]]
    |1={{clade
      |1=[[Heterotrichea]]
      |2=[[Karyorelictea]]
       }}
    |label2=[[Postciliodesmatophora]]
    |2={{clade
       |1=[[Desmata]]
       |2=[[Spirotrichia]]
       }}
     }}
  |label2=[[Miozoa]]
  |2={{clade
    |1=[[Colponemea]]<!--T C-S marks the visibly paraphyletic "Protalveoalata" for this and the Acavomonadea-->
    |2={{clade
      |label1=Acavomonadia
      |1=[[Acavomonadea]]
      |label2=[[Myzozoa]]
      |2={{clade
        |label1=[[Apicomplexa]]
        |1={{clade
           |1=[[Apicomonada]]
           |2=[[Sporozoa]]
           }}
        |label2=[[Dinozoa]]
        |2={{clade
           |1=[[Dinoflagellata]]
           |2=[[Perkinsea]]
           }}
         }}
       }}
     }}
   }}
}}

===Taxonomy===
'''Alveolata''' <small>Cavalier-Smith 1991</small> [Alveolatobiontes]
* Phylum [[Ciliophora]] <small>Doflein 1901 stat. n. Copeland 1956</small> [Ciliata <small>Perty 1852</small>; Infusoria <small>Bütschli 1887</small>; Ciliae, Ciliozoa, Cytoidea, Eozoa, Heterocaryota, Heterokaryota]
** Subphylum [[Postciliodesmatophora]] <small>Gerassimova & Seravin 1976</small>
*** Class [[Heterotrichea]] <small>Stein 1859</small>
*** Class [[Karyorelictea]] <small>Corliss 1974</small>
** Subphylum [[Intramacronucleata]] <small>Lynn 1996</small>
*** Class ?[[Mesodiniea]] <small>Chen et al. 2015</small>
*** Infraphylum Lamellicorticata
**** Class [[Litostomatea]] <small>Small & Lynn 1981</small>
**** Class [[Armophorea]] <small>Lynn 2004</small>
**** Class [[Cariacotrichea]] <small>Orsi et al. 2011</small>
**** Class [[Spirotrichea]] <small>Bütschli 1889</small>
**** Infraphylum Ventrata <small>Cavalier-Smith 2004</small> [Conthreep <small>Lynn 2012</small>]
**** Order ?[[Discotrichida]] <small>Chen et al. 2015</small>
**** Class [[Protocruziea]] <small>Chen et al. 2015</small> [Protocruziidia <small>de Puytorac, Grain & Mignot 1987</small>]
**** Class [[Colpodea]] <small>Small & Lynn 1981</small>
**** Class [[Nassophorea]] <small>Small & Lynn 1981</small>
**** Class [[Phyllopharyngea]] <small>de Puytorac et al. 1974</small>
**** Class [[Prostomatea]] <small>Schewiakoff 1896</small>
**** Class [[Plagiopylea]] <small>Small & Lynn 1985 sensu Lynn 2008</small>
**** Class [[Oligohymenophorea]] <small>de Puytorac et al. 1974</small>
* Phylum [[Miozoa]] <small>Cavalier-Smith 1987</small>
** Subphylum Colponemidia <small>Tikhonenkov, Mylnikov & Keeling 2013</small>
*** Class [[Colponemea]] <small>Cavalier-Smith 1993</small>
** Subphylum Acavomonadia <small>Tikhonenkov et al. 2014</small>
*** Class [[Acavomonadea]] <small>Tikhonenkov et al. 2014</small>
** Subphylum [[Myzozoa]] <small>Cavalier-Smith 2004</small>
*** Infraphylum [[Apicomplexa]] <small>Levine 1970 emend. Adl et al. 2005</small>
**** Order ?[[Vitrellida]] <small>Cavalier-Smith 2017</small>
**** Class ?[[Myzomonadea]] <small>Cavalier-Smith & Chao 2004 sensu Ruggiero et al. 2015</small>
**** Class [[Chromerida|Chromerea]]
**** Order [[Colpodellida]] <small>Patterson & Zölffel 1991</small> [Spiromonadida <small>Krylov & Mylnikov 1986</small>]
**** Superclass [[Sporozoa]] <small>Leuckart 1879 stat. nov. Cavalier-Smith 2013</small>  [Gamontozoa]
***** Class [[Blastogregarinida]] <small>Chatton & Villeneuve 1936</small> [Blastogregarinina; Blastogregarinorina <small>Chatton & Villeneuve 1936</small>]
***** Class [[Paragregarea]] <small>Cavalier-Smith 2014</small>
***** Class [[Gregarinomorphea]] <small>Grassé 1953</small>
***** Class [[Coccidiomorphea]] <small>Doflein 1901</small>
*** Infraphylum [[Dinozoa]] <small>Cavalier-Smith 1981 emend. 2003</small>
**** Order ?[[Acrocoelida]] <small>Cavalier-Smith & Chao 2004</small>
**** Order ?[[Rastromonadida]] <small>Cavalier-Smith & Chao 2004</small>
**** Class [[Squirmidea]] <small>Norén 1999 stat. nov. Cavalier-Smith 2014</small>
**** Superclass [[Perkinsozoa]] <small>Norén et al. 1999 s.s.</small>
***** Class [[Perkinsea]] <small>Levine 1978</small> [Perkinsasida <small>Levine 1978</small>]
**** Superclass [[Dinoflagellata]] <small>Butschli 1885 stat. nov. Cavalier-Smith 1999 sensu Cavalier-Smith 2013</small> [Dinozoa <small>Cavalier-Smith 1981</small>]
***** Class [[Pronoctilucea]]
***** Class [[Ellobiopsea]] <small>Cavalier-Smith 1993</small> [Ellobiophyceae <small>Loeblich III 1970</small>; Ellobiopsida <small>Whisler 1990</small>]
***** Class [[Myzodinea]] <small>Cavalier-Smith 2017</small>
***** Class [[Oxyrrhea]] <small>Cavalier-Smith 1987</small>
***** Class [[Syndinea]] <small>Chatton 1920 s.l.</small> [Syndiniophyceae <small>Loeblich III 1970 s.s.</small>; Syndina <small>Cavalier-Smith</small>]
***** Class [[Endodinea]] <small>Cavalier-Smith 2017</small>
***** Class [[Noctilucales|Noctiluciphyceae]] <small>Fensome et al. 1993</small> [Noctilucae <small>Haeckel 1866</small>; Noctilucea <small>Haeckel 1866 stat. nov.</small>; Cystoflagellata <small>Haeckel 1873 stat. nov. Butschli 1887</small>]
***** Class [[Dinophyceae]] <small>Pascher 1914</small> [Peridinea <small>Ehrenberg 1830 stat. nov. Wettstein</small>]

==Development==
The development of plastids among the alveolates is intriguing. Cavalier-Smith proposed the alveolates developed from a chloroplast-containing ancestor, which also gave rise to the [[Chromista]] (the [[chromalveolate]] hypothesis). Other researchers have speculated that the alveolates originally lacked plastids and possibly the dinoflagellates and Apicomplexa acquired them separately. However, it now appears that the alveolates, the dinoflagellates, the Chromerida and the [[Heterokont|heterokont algae]] acquired their plastids from a red alga with evidence of a common origin of this organelle in all these four clades.<ref name=Janouskovec2010>{{cite journal | last1 = Janouskovec | first1 = J | last2 = Horák | first2 = A | last3 = Oborník | first3 = M | last4 = Lukes | first4 = J | last5 = Keeling | first5 = PJ | year = 2010 | title = A common red algal origin of the apicomplexan, dinoflagellate, and heterokont plastids | journal = Proc Natl Acad Sci USA | volume = 107 | issue = 24| pages = 10949–54 | doi=10.1073/pnas.1003335107 | pmid=20534454 | pmc=2890776| bibcode = 2010PNAS..10710949J | doi-access = free }}</ref>

==Evolution==
A Bayesian estimate places the evolution of the alveolate group at ~{{ma|850}}.<ref name=Berney2006>{{cite journal | last1 = Berney | first1 = C | last2 = Pawlowski | first2 = J | year = 2006 | title = A molecular time-scale for eukaryote evolution recalibrated with the continuous microfossil record | journal = Proc Biol Sci | volume = 273 | issue = 1596| pages = 1867–72 | doi=10.1098/rspb.2006.3537| pmc = 1634798 | pmid=16822745}}</ref> The Alveolata consist of [[Myzozoa]], [[Ciliates]], and Colponemids. In other words, the term Myzozoa, meaning "to siphon the contents from prey", may be applied informally to the common ancestor of the subset of alveolates that are neither ciliates nor colponemids. Predation upon algae is an important driver in alveolate evolution, as it can provide sources for endosymbiosis of novel plastids.  The term Myzozoa is therefore a handy concept for tracking the history of the alveolate phylum.

The ancestors of the alveolate group may have been photosynthetic.<ref name=Reyes-Prieto>{{cite journal|last1=Reyes-Prieto|first1=A|last2=Moustafa|first2=A|last3=Bhattacharya|first3=D|title=Multiple genes of apparent algal origin suggest ciliates may once have been photosynthetic.|journal=Curr. Biol.|date=2008|volume=18|issue=13|pages=956–62|doi=10.1016/j.cub.2008.05.042|pmid=18595706|pmc=2577054|bibcode=2008CBio...18..956R}}</ref> The ancestral alveolate probably possessed a [[plastid]]. Chromerids, apicomplexans, and peridinin dinoflagellates have retained this [[organelle]].<ref>{{cite journal |vauthors=Moore RB, Oborník M, Janouskovec J, Chrudimský T, Vancová M, Green DH, Wright SW, Davies NW, Bolch CJ, Heimann K, Slapeta J, Hoegh-Guldberg O, Logsdon JM, Carter DA |title=A photosynthetic alveolate closely related to apicomplexan parasites |journal=Nature |volume=451 |issue=7181 |pages=959–963 |year=2008 |pmid=18288187 |doi=10.1038/nature06635 |bibcode=2008Natur.451..959M |s2cid=28005870 }}</ref> Going one step even further back, the chromerids, the peridinin dinoflagellates and the [[Heterokont|heterokont algae]] have been argued to possess a monophyletic plastid lineage in common, i.e. acquired their plastids from a [[red alga]],<ref name="Janouskovec2010"/> and so it seems likely that the common ancestor of alveolates and heterokonts was also photosynthetic.

In one school of thought the common ancestor of the [[dinoflagellates]], [[apicomplexans]], ''[[Colpodella]]'', [[Chromerida]], and ''[[Voromonas]]'' was a myzocytotic predator with two heterodynamic [[flagella]], [[micropore]]s, [[trichocyst]]s, [[rhoptries]], [[microneme]]s, a polar ring and a coiled open sided [[conoid]].<ref name=Kuvardina2002>{{cite journal | last1 = Kuvardina | first1 = ON | last2 = Leander | first2 = BS | last3 = Aleshin | first3 = VV | last4 = Myl'nikov | first4 = AP | last5 = Keeling | first5 = PJ | last6 = Simdyanov | first6 = TG | year = 2002 | title = The phylogeny of colpodellids (Alveolata) using small subunit rRNA gene sequences suggests they are the free living sister group to apicomplexans | journal = J Eukaryot Microbiol | volume = 49 | issue = 6| pages = 498–504 | doi=10.1111/j.1550-7408.2002.tb00235.x | pmid=12503687| title-link = colpodellid | s2cid = 4283969 }}</ref> While the common ancestor of alveolates may also have possessed some of these characteristics, it has been argued that Myzocytosis was not one of these characteristics, as ciliates ingest prey by a different mechanism.<ref name=Tikhonenkov14/>

An ongoing debate concerns the number of membranes surrounding the plastid across apicomplexans and certain dinoflagellates, and the origin of these membranes. This ultrastructural character can be used to group organisms and if the character is in common, it can imply that phyla had a common photosynthetic ancestor. On the basis that apicomplexans possess a plastid surrounded by four membranes, and that peridinin dinoflagellates possess a plastid surrounded by three membranes, Petersen et al.<ref>{{cite journal |vauthors=Petersen J, Ludewig AK, Michael V, Bunk B, Jarek M, Baurain D, Brinkmann H |title=''Chromera velia'', endosymbioses and the rhodoplex hypothesis—plastid evolution in cryptophytes, alveolates, stramenopiles, and haptophytes (CASH lineages) |journal=Genome Biol Evol |volume=6 |issue=3 |pages=666–684 |year=2014 |pmid=24572015 |pmc=3971594 |doi=10.1093/gbe/evu043 }}</ref> have been unable to rule out that the shared stramenopile-alveolate plastid could have been recycled multiple times in the alveolate phylum, the source being stramenopile-alveolate donors, through the mechanism of ingestion and [[endosymbiosis]].

Ciliates are a model alveolate, having been genetically studied in great depth over the longest period of any alveolate lineage. They are unusual among eukaryotes in that reproduction involves a [[micronucleus]] and a [[macronucleus]]. Their reproduction is easily studied in the lab, and made them a model eukaryote historically. Being entirely predatory and lacking any remnant plastid, their development as a phylum illustrates how predation and autotrophy<ref name="Reyes-Prieto"/> are in dynamic balance and that the balance can swing one way or other at the point of origin of a new phylum from mixotrophic ancestors, causing one ability to be lost.

<gallery class="center" mode="nolines" widths=200 heights=200>
File:Paramecium caudatum Ehrenberg, 1833.jpg|''[[Paramecium|Paramecium caudatum]]'' ([[Ciliophora]])
File:Mikrofoto.de-Glockentierchen-1.jpg|''[[Vorticella]]'' ([[Ciliophora]]) (left)
File:Plasmodium.jpg|''[[Plasmodium falciparum]]'' ([[Apicomplexa]]) in blood
File:Emaxima oocysts usda.jpg|''[[Eimeria|Eimeria maxima]]'' ([[Apicomplexa]])
File:Dinophysis acuminata.jpg|''[[Dinophysis|Dinophysis acuminata]]'' ([[Dinoflagellata]])
</gallery>

== Epigenetics ==
Few [[alga]]e have been studied for [[epigenetics]].<ref name="Develop methodologies for epigenetics"/> Those for which epigenetic data are available include some algal alveolates.<ref name="Develop methodologies for epigenetics">{{Cite book|year=2023|publisher=Wiley|doi=10.1002/9781119821946|pages=383–411|title=Epigenetics in Aquaculture |hdl=10261/191758 |isbn=978-1-119-82191-5 |editor-last1=Piferrer |editor-last2=Wang |editor-first1=Francesc |editor-first2=Han-Ping }}</ref>

==References==
{{Reflist|2}}

==External links==
{{Wikispecies|Alveolata}}
* [http://tolweb.org/Alveolates/2379 Tree of Life: Alveolates]

{{Eukaryota classification}}
{{Chromalveolate diseases}}
{{Alveolata}}
{{Taxonbar|from=Q448746}}

[[Category:Alveolata| ]]
[[Category:Infrakingdoms]]