Cercozoa

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Cercozoa
Cercomonas sp.jpg
Cercomonas
Scientific classification edit
(unranked): SAR
(unranked): Rhizaria
Phylum: Cercozoa
Cavalier-Smith 1998[1]
Groups[4]

Filosa

Endomyxa

The Cercozoa are a group of single-celled eukaryotes. They lack shared morphological characteristics at the microscopic level,[5] being defined by molecular phylogenies of rRNA and actin or polyubiquitin.[6]

Characteristics[edit]

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[4] and have proven difficult to define in terms of structural characteristics, although their unity is strongly supported by genetic studies. Cercozoa are closely related to Foraminifera and Radiolaria, amoeboids that usually have complex shells, and together with them form a supergroup called the Rhizaria.

Types[edit]

They are sometimes grouped by whether they are "filose" or "reticulose".[7]

Filose (subphylum Filosa)[edit]

The best-known Cercozoa are the euglyphids, filose amoebae with shells of siliceous scales or plates, which are commonly found in soils, nutrient-rich waters, and on aquatic plants. Some other filose amoebae produce organic shells, including the tectofilosids and Gromia. They were formerly classified with the euglyphids as the Testaceafilosia. This group is not monophyletic, but nearly all studied members fall in or near the Cercozoa, related to similarly shelled flagellates. Other notable filose cercozoans include the cercomonads, which are common soil flagellates.

Reticulose (subphylum Endomyxa)[edit]

Another important group placed here are the chlorarachniophytes, strange amoebae that form a reticulating net. They are set apart by the presence of chloroplasts, which apparently developed from an ingested green alga. They are 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.

Chlorarachniophytes are sometimes considered Filosa, rather than Endomyxa, while groups such as Gromia are considered Endomyxa.[8] Filosa is apparently a monophyletic group, but Endomyxa is paraphyletic.[9]

Ungrouped[edit]

In addition, three groups that are traditionally considered heliozoans belong here: the Heliomonadida, Desmothoracida, and Gymnosphaerida, which were recently grouped into the new class of Granofilosea.[7]

Finally, cercozoans include the Phaeodarea, marine protozoa that were previously considered radiolarians.

Classification[edit]

The exact composition and classification of the Cercozoa are still being worked out. A general scheme is:

Class Chlorarachnea Chlorarachniophyta
Class Proteomyxidea Gymnophryida, Heliomonadida, Desmothoracida, Gymnosphaerida, etc.
Class Sarcomonadea Cercomonadida
Class Imbricatea / Silicofilosea Euglyphida and Thaumatomonadida
Class Thecofilosea Tectofilosida and Cryomonadida
Class Phaeodarea
Class Ebridea Ebridea

In addition two groups of parasites, the Phytomyxea and Ascetosporea, and the shelled amoeba Gromia may be basal Cercozoa, although some trees place them closer to the Foraminifera.

The spongomonads have been included here, but more recently have been considered Amoebozoa.[citation needed]

Some other small groups of protozoans are considered Cercozoa but are of uncertain placement, and it is likely many obscure genera will turn out to be cercozoans with further study.

Phylogeny[edit]

Phylogeny based on Bass et al. 2009,[7] Howe etal. 2011[10] and Silar 2016.[11]

Rhizaria

Phytomyxea  

Vampyrellidea  

Filosa

Skiomonadea  

Chlorarachniophyceae  

Granofilosea  

Monadofilosa

Metromonadea  

Cercomonadida  

Glissomonadida-Sainourida clade  

Ventrifilosa

Silicofilosea  

Thecofilosea  

Marimyxia

Reticulosida  

Gromiidea  

Ascetosporea  

Retaria

Sticholonchea

Polycystinea

Acantharea

Foraminifera

Cercozoa

Taxonomy[edit]

Phylum Cercozoa[10][11][12][13][14]

  • Family ?Gymnophrydiidae
  • Family ?Gymnophryidae Mikrjukov & Mylnikov 1996
  • Family ?Rhizoplasmidae Cavalier-Smith & Bass 2009
  • Order ?Gymnosphaerida Poche 1913 emend. Mikrjukov 2000 [Axoplasthelida]
    • Family Gymnosphaeridae Poche 1913 [Hedraiophryidae; Gymnidae; Wagnerellidae Poche 1913]
  • Clade Marimyxia Cavalier-Smith 2017
    • Order Reticulosida Cavalier-Smith 2003 emend. Bass et al. 2009
    • Class Gromiidea Cavalier-Smith 2003
      • Order Gromiida Claparède & Lachmann 1856 s.s.
    • Class Ascetosporea Desportes & Ginsburger-Vogel, 1977 emend. Cavalier-Smith 2009 [Aplosporidies Caullery & Mesnil, 1899; Stellatosporea; Ascetospora Sprague 1979]
      • Order Claustrosporida Cavalier-Smith 2003
      • Order Paradiniida Cavalier-Smith 2009
      • Order Mikrocytida Hartikainen et al. 2014
      • Order Paramyxida Chatton 1911 [Paramyxea Chatton 1911; Paramyxidea Chatton 1911; Paramyxa]
      • Order Haplosporida Caullery & Mesnil 1899 [Balanosporida Sprague, 1979; Haplosporidia Hall, 1953; Haplosporea Caullery 1953; Haplospora Margulis & Schwartz, 1998; Haplosporidiidea Poche, 1913; Haplosporidies Caullery and Mesnil, 1905]
  • Class Phytomyxea Engler & Prantl 1897 em. Cavalier-Smith 1993 [Phytomyxinae Engler & Prantl, 1897; Phytomyxinea Poche, 1913]
  • Class Vampyrellidea Cavalier-Smith 2017 [Cristivesiculatia Page 1987 stat. nov. Cavalier-Smith 1993]
    • Order Vampyrellida West 1901 emend. Hess et al. 2012 [Aconchulinida de Saedeleer 1934 emend. Bass et al. 2009; Cristivesiculatida Page 1987]
  • Subphylum Filosa Leidy 1879 emend. Cavalier-Smith 2003

Recently an orphan protist Quadricilia rotundata finally finds fts phylogenetic home in Cercozoa.[15]

References[edit]

  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.
  2. ^ 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.
  3. ^ 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.
  4. ^ a b 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.
  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 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.
  8. ^ "Cercozoa". Retrieved 2009-05-21.
  9. ^ Yasuhide Nakamura, Ichiro Imai, Atsushi Yamaguchi, Akihiro Tuji, Fabrice Not, and Noritoshi Suzuki. 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. (See External links below).
  10. ^ a b Howe; et al. (2011), "Novel Cultured Protists Identify Deep-branching Environmental DNA Clades of Cercozoa: New Genera Tremula, Micrometopion, Minimassisteria, Nudifila, Peregrinia", Protist, 162: 332–372, doi:10.1016/j.protis.2010.10.002, PMID 21295519
  11. ^ a b Silar, Philippe (2016), "Protistes Eucaryotes: Origine, Evolution et Biologie des Microbes Eucaryotes", HAL archives-ouvertes: 1–462
  12. ^ Adl; et al. (28 September 2012), "The Revised Classification of Eukaryotes" (PDF), Journal of Eukaryotic Microbiology, 59 (5): 429–493, doi:10.1111/j.1550-7408.2012.00644.x, PMC 3483872, PMID 23020233
  13. ^ Ruggiero; et al. (2015), "Higher Level Classification of All Living Organisms", PLoS ONE, 10 (4): e0119248, doi:10.1371/journal.pone.0119248, PMC 4418965, PMID 25923521
  14. ^ Cavalier-Smith, Thomas (5 September 2017). "Kingdom Chromista and its eight phyla: a new synthesis emphasising periplastid protein targeting, cytoskeletal and periplastid evolution, and ancient divergences". Protoplasma: 1–61. doi:10.1007/s00709-017-1147-3.
  15. ^ An Orphan Protist Quadricilia rotundata Finally Finds Its Phylogenetic Home in Cercozoa Article in Journal of Eukaryotic Microbiology · January 2018 DOI: 10.1111/jeu.12502 Akinori Yabuki at Japan Agency for Marine-Earth Science Technology

External links[edit]