Cercozoa

Cercozoa
Cercomonas
Scientific classification Edit this classification
Domain: Eukaryota
Supergroup: Rhizaria
Phylum: Cercozoa
Cavalier-Smith 1998, emend. Adl et al. 2005
Subgroups
Synonyms

Cercozoa is a phylum of diverse single-celled eukaryotes. They lack shared morphological characteristics at the microscopic level, and are instead united 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.

Characteristics

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 and have proven difficult to define in terms of structural characteristics, although their unity is strongly supported by phylogenetic studies.

Diversity

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

Ecology

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

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.

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 cercozoans 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.

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.

Systematics

Paraphyletic Cercozoa
Rhizaria
Monophyletic Cercozoa
Rhizaria

Cercozoa is composed of two groups: Filosa and Endomyxa. With Heliomorpha added, Endomyxa is polyphyletic. Recent phylogenomic analyses with better sampling recovered a sister relationship between Filosa and Endomyxa. According to multigene phylogenetic analyses, Monadofilosa is a robust clade with its analyzed groups. Some works proposed to exclude Endomyxa from Cercozoa and transferring it to Retaria or keeping it directly under Rhizaria. A more recent phylogenomic analysis recovered both Monadofilosa and Reticulofilosa as monophyletic within the clade Filosa.

In addition to the known Granofilosea, Chlorarachnea and Monadofilosa, 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) and Aquavolonida (Novel Clade 10). Some genera have been classified as incertae sedis within the group. Pseudospora is in Filosa when Filosa is used.

References

  1. ↑ 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.
  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. ↑ Chantangsi, C. (2009). Comparative morphology and molecular evolution of marine interstitial cercozoans. PhD thesis. University of British Columbia.
  5. ↑ "SYSTEMATIC BIOLOGY: CERCOZOA". Archived from the original on 2015-04-02. Retrieved 2009-03-28.
  6. 1 2 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.
  7. 1 2 3 4 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
  8. ↑ 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.
  9. ↑ 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.
  10. ↑ 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.
  11. 1 2 Harder C, Rønn R, Brejnrod A, et al. (8 March 2016). "Local diversity of heathland Cercozoa explored by in-depth sequencing". The ISME Journal. 10 (10): 2488–2497. doi:10.1038/ismej.2016.31. PMC 5030685. PMID 26953604.
  12. ↑ Bass D, Silberman JD, Brown MW, Pearce RA, Tice AK, Jousset A, Geisen S, Hartikainen H (23 February 2016). "Coprophilic amoebae and flagellates, including Guttulinopsis, Rosculus and Helkesimastix, characterise a divergent and diverse rhizarian radiation and contribute to a large diversity of faecal-associated protists". Environmental Microbiology. 18 (5): 1604–1619. doi:10.1111/1462-2920.13235. PMID 26914587.
  13. ↑ 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.
  14. 1 2 3 4 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.
  15. ↑ Eglit, Yana (2022-12-16). "Transforming the eukaryotic tree of life through isolation, characterisation, and phylogenetics of novel free-living protists". Faculty of Graduate Studies Online Theses – via DalSpace Institutional Repository.
  16. ↑ Adl, Sina M.; Bass, David; Lane, Christopher E.; Lukeš, Julius; Schoch, Conrad L.; Smirnov, Alexey; Agatha, Sabine; Berney, Cedric; Brown, Matthew W.; Burki, Fabien; Cárdenas, Paco; Čepička, Ivan; Chistyakova, Lyudmila; del Campo, Javier; Dunthorn, Micah (2018-09-26). "Revisions to the Classification, Nomenclature, and Diversity of Eukaryotes". Journal of Eukaryotic Microbiology. 66 (1): 4–119. doi:10.1111/jeu.12691. ISSN 1550-7408. PMC 6492006. PMID 30257078.
  17. ↑ 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.
  18. ↑ Bass D, Tikhonenkov DV, Foster R, Dyal P, Janouškovec J, Keeling PJ, Gardner M, Neuhauser S, Hartikainen H, Mylnikov AP, Berney C (2018). "Rhizarian 'Novel Clade 10' Revealed as Abundant and Diverse Planktonic and Terrestrial Flagellates, including Aquavolon n. gen". Journal of Eukaryotic Microbiology. 65 (6): 828–842. doi:10.1111/jeu.12524. PMC 6282753. PMID 29658156.
  19. ↑ Kiss, Áron Keve; Török, Júlia Katalin; Ács, Éva; Kiss, Keve Tihamér (2009). "Pseudodifflugia klarae nov. spec., Bereczkya minuta nov. gen. nov. spec. and Paramphitrema muelleri nov. spec.: Three New Filose Testate Amoebae from the Plankton of the River Danube". Acta Protozoologica. 48 (2) – via ejournals.
  20. ↑ Nicholls, Kenneth H. (2012-09-28). "Zoelucasa sablensis n. gen. et n. sp. (Cercozoa, Incertae Sedis), a New Scale-covered Flagellate from Marine Sandy Shores". Acta Protozoologica. 51 (2): 113–117. doi:10.4467/16890027AP.12.009.0513.
  21. ↑ Scoble, Josephine M.; Cavalier-Smith, Thomas (June 2014). "Scale evolution, sequence phylogeny, and taxonomy of thaumatomonad Cercozoa: 11 new species and new genera Scutellomonas, Cowlomonas, Thaumatospina and Ovaloplaca". European Journal of Protistology. 50 (3): 270–313. doi:10.1016/j.ejop.2013.12.005. PMID 24667165.