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Cercozoa is a phylum of diverse single-celled eukaryotes.[3][4] They lack shared morphological characteristics at the microscopic level,[5] and are instead defined by molecular phylogenies of rRNA and actin or polyubiquitin.[6] They were the first major eukaryotic group to be recognized mainly through molecular phylogenies.[7] They are the natural predators of many species of bacteria. They are closely related to the phylum Retaria, comprising amoeboids that usually have complex shells, and together form a supergroup called Rhizaria.[8]


The group includes most amoeboids and flagellates that feed by means of filose pseudopods. These may be restricted to part of the cell surface, but there is never a true cytostome or mouth as found in many other protozoa. They show a variety of forms[9] and have proven difficult to define in terms of structural characteristics, although their unity is strongly supported by phylogenetic studies.


Some cercozoans are grouped by whether they are "filose" or "reticulose" in the behavior of their cytoskeleton when moving:[10]

  • Filose, meaning their pseudopods develop as filopodia. For example:
    • Euglyphids, filose amoebae with shells of siliceous scales or plates, which are commonly found in soils, nutrient-rich waters, and on aquatic plants.
    • Gromia, a shelled amoeba.
    • Tectofilosids, filose amoebae that produce organic shells.
    • Cercomonads, common soil-dwelling amoeboflagellates.
  • Reticulose, meaning they form a reticulating net of pseudopods. For example:
    • Chlorarachniophytes, set apart by the presence of chloroplasts bound by four membranes and still possess a vestigial nucleus, called a nucleomorph. As such, they have been of great interest to researchers studying the endosymbiotic origins of organelles.

Other important ecological groups are:


As well as being highly diverse in morphology and physiology, Cercozoa also shows high ecological diversity.[12] The phylum Cercozoa includes many of the most abundant and ecologically significant protozoa in soil, marine and freshwater ecosystems.[7]

Soil-dwelling cercozoans are one of the dominant groups of free-living eukaryotic microorganisms found in temperate soils, accounting for around 30% of identifiable protozoan DNA in arid or semi-arid soils and 15% in more humid soils. In transcriptomic analyses they account for 40-60% of all identifiable protozoan RNA found in forest and grassland soils. They also comprise 9-24% of all operational taxonomic units found in the ocean floor.[12]

Some cercozoa are coprophilic or coprozoic, meaning they use feces as a source of nutrients or as transport through animal hosts. The faecal habitat is an understudied reservoir of microbial eukaryotic diversity, dominated by amoeboflagellates from the phylum Cercozoa. Strongly coprophilic examples of cercozoa are the flagellates Cercomonas, Proleptomonas and Helkesimastix, and the sorocarpic amoeba Guttulinopsis. Many new cercozoan lineages, especially among sarcomonads, have been discovered through phylogenetic sampling of feces because they appear preferentially in this medium.[13]

Cercozoan bacterivores (i.e. predators of bacteria) are highly diverse and important in the plant phyllosphere, the leaf surfaces of plants. Particularly sarcomonads, with their ability to cyst, feed and multiply within hours, are perfectly adapted to the fluctuating environmental factors in the phyllosphere. Their predation causes shifts in the bacterial communities: they reduce populations of alphaproteobacteria and betaproteobacteria, which are less resistant to their grazing, in favour of other bacterial populations such as gammaproteobacteria.[14]


Paraphyletic Cercozoa[8] Rhizaria Filosa



(=Cercozoa) Retaria






Monophyletic Cercozoa[15] Rhizaria Cercozoa Filosa




Lapot gusevi





The initial molecular phylogenetic analyses of Cercozoa, based on ribosomal RNA and tubulins, recognized two subphyla, Endomyxa and Filosa, and showed a close relationship with phylum Retaria.[10][16]

However, the monophyly of the group was still uncertain. Posterior phylogenomic analyses consistently recovered Cercozoa as a paraphyletic group, and Endomyxa was often clustered with Retaria.[17][18][19] As a result, the current taxonomy of Rhizaria places Endomyxa inside the phylum Retaria instead of Cercozoa, which has therefore become synonymous with Filosa.[8]

Despite the taxonomic change of Endomyxa into phylum Retaria, thanks to better phylogenomic sampling a 2019 analysis recovered phylum Cercozoa as a monophyletic group, with Endomyxa being the sister group to Filosa. In the same analysis, Endomyxa, Filosa, Reticulofilosa and Monadofilosa are proven to be monophyletic too.[15]

In addition to Endomyxa and Filosa, a variety of clades inside Cercozoa have been discovered in other analyses and have slowly been described and named, such as Tremulida (previously known as Novel Clade 11)[16] and Aquavolonida (Novel Clade 10),[20] although their specific positions among the two main cercozoan subphyla have yet to be refined.


The classification of Cercozoa as revised in 2018,[8] with the addition of Endomyxa:[15]

Phylum Cercozoa Cavalier-Smith 1998 emend. 2018
Clade Filosa
  Subphylum Reticulofilosa Cavaler-Smith 1997
   Class Chlorarachnea Hibberd & Norris 1984 (as Chlorarachniophyceae)
   Class Granofilosea Cavalier-Smith & Bass 2009
   Class Skiomonadea Cavalier-Smith 2012
  Subphylum Monadofilosa Cavalier-Smith 1997
   Superclass Eoglissa Cavalier-Smith 2011 emend. 2018
    Class Metromonadea Cavalier-Smith 2007
    Class Helkesea Cavalier-Smith 2018
   Superclass Ventrifilosa Cavalier-Smith 2012 emend. 2018
    Class Sarcomonadea Cavalier-Smith 1993 stat. nov. 1995 emend. 2018
     Subclass Paracercomonada Cavalier-Smith 2018
     Subclass Pediglissa Cavalier-Smith 2018
    Class Imbricatea Cavalier-Smith 2003 emend. 2018
     Subclass Placonuda Cavalier-Smith 2012
     Subclass Placoperla Cavalier-Smith 2012
     Subclass Krakenia Cavalier-Smith 2018
    Class Thecofilosea Cavalier-Smith 2003 emend. 2012
     Subclass Ventricleftia Cavalier-Smith 2018
     Subclass Eothecia Cavalier-Smith 2012
     Subclass Phaeodaria Haeckel 1879
     Subclass Tectosia Cavalier-Smith 2012
Clade Endomyxa
  Superclass Marimyxia Cavalier-Smith 2018
   Class Gromiidea Cavalier-Smith 2003 emend. 2018
   Class Ascetosporea Sprague 1979 stat. nov. Cavalier-Smith 2002
  Superclass Proteomyxia Lankester 1885 ex Cavalier-Smith 2018
   Class Vampyrellidea Cavalier-Smith 2018
   Class Phytomyxea Engler & Prantl 1897



  1. ^ Cavalier-Smith, T. (1998). "A revised six-kingdom system of life". Biological Reviews of the Cambridge Philosophical Society. 73 (3): 203–266. doi:10.1111/j.1469-185X.1998.tb00030.x. PMID 9809012. S2CID 6557779.
  2. ^ Cavalier-Smith T (1997). "Amoeboflagellates and mitochondrial cristae in eukaryote evolution: megasystematics of the new protozoan subkingdoms eozoa and neozoa". Archiv für Protistenkunde. 147 (3–4): 237–258. doi:10.1016/S0003-9365(97)80051-6. ISSN 0003-9365.
  3. ^ Nikolaev SI, Berney C, Fahrni JF, et al. (May 2004). "The twilight of Heliozoa and rise of Rhizaria, an emerging supergroup of amoeboid eukaryotes". Proc. Natl. Acad. Sci. U.S.A. 101 (21): 8066–71. doi:10.1073/pnas.0308602101. PMC 419558. PMID 15148395.
  4. ^ Hoppenrath, M.; Leander B.S. (2006). "Ebriid phylogeny and the expansion of the Cercozoa". Protist. 157 (3): 279–90. doi:10.1016/j.protis.2006.03.002. PMID 16730229.
  5. ^ Chantangsi, C. (2009). Comparative morphology and molecular evolution of marine interstitial cercozoans. PhD thesis. University of British Columbia.
  6. ^ "SYSTEMATIC BIOLOGY: CERCOZOA". Retrieved 2009-03-28.
  7. ^ a b Bass D, Cavalier-Smith T (1 November 2004). "Phylum-specific environmental DNA analysis reveals remarkably high global biodiversity of Cercozoa (Protozoa)". International Journal of Systematic and Evolutionary Microbiology. 54 (6): 2393–2404. doi:10.1099/ijs.0.63229-0. PMID 15545489.
  8. ^ a b c d Cavalier-Smith, Thomas; E. Chao, Ema; Lewis, Rhodri (2018), "Multigene phylogeny and cell evolution of chromist infrakingdom Rhizaria: contrasting cell organisation of sister phyla Cercozoa and Retaria", Protoplasma, 255 (5): 1517–1574, doi:10.1007/s00709-018-1241-1, PMC 6133090, PMID 29666938
  9. ^ Cavalier-Smith T, Chao EE (October 2003). "Phylogeny and classification of phylum Cercozoa (Protozoa)" (PDF). Protist. 154 (3–4): 341–58. doi:10.1078/143446103322454112. PMID 14658494.
  10. ^ a b c Bass D, Chao EE, Nikolaev S, et al. (February 2009). "Phylogeny of Novel Naked Filose and Reticulose Cercozoa: Granofilosea cl. n. and Proteomyxidea Revised". Protist. 160 (1): 75–109. doi:10.1016/j.protis.2008.07.002. PMID 18952499.
  11. ^ Nakamura, Yasuhide; Imai, Ichiro; Yamaguchi, Atsushi; Tuji, Akihiro; Not, Fabrice; Suzuki, Noritoshi (2015). "Molecular Phylogeny of the Widely Distributed Marine Protists, Phaeodaria (Rhizaria, Cercozoa)". Protist. 166 (3): 363–373. doi:10.1016/j.protis.2015.05.004. PMID 26083083.
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  14. ^ Flues S, Bass D, Bonkowski M (15 June 2017). "Grazing of leaf-associated Cercomonads (Protists: Rhizaria: Cercozoa) structures bacterial community composition and function". Environmental Microbiology. 19 (8): 3297–3309. doi:10.1111/1462-2920.13824. PMID 28618206.
  15. ^ a b c Irwin, Nicholas A.T.; Tikhonenkov, Denis V.; Hehenberger, Elisabeth; Mylnikov, Alexander P.; Burki, Fabien; Keeling, Patrick J. (2019-01-01). "Phylogenomics supports the monophyly of the Cercozoa". Molecular Phylogenetics and Evolution. 130: 416–423. doi:10.1016/j.ympev.2018.09.004. ISSN 1055-7903. PMID 30318266. S2CID 52982396.
  16. ^ a b Howe, Alexis T.; Bass, David; Scoble, Josephine M.; Lewis, Rhodri; Vickerman, Keith; Arndt, Hartmut; Cavalier-Smith, Thomas (2011). "Novel Cultured Protists Identify Deep-branching Environmental DNA Clades of Cercozoa: New Genera Tremula, Micrometopion, Minimassisteria, Nudifila, Peregrinia". Protist. 162 (2): 332–372. doi:10.1016/j.protis.2010.10.002. ISSN 1434-4610. PMID 21295519.
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Cercozoa: Brief Summary

provided by wikipedia EN

Cercozoa is a phylum of diverse single-celled eukaryotes. They lack shared morphological characteristics at the microscopic level, and are instead defined by molecular phylogenies of rRNA and actin or polyubiquitin. They were the first major eukaryotic group to be recognized mainly through molecular phylogenies. They are the natural predators of many species of bacteria. They are closely related to the phylum Retaria, comprising amoeboids that usually have complex shells, and together form a supergroup called Rhizaria.

Wikipedia authors and editors
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wikipedia EN