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The Cercozoa are a group of single-celled eukaryotes. They lack shared morphological characteristics at the microscopic level, being defined by molecular phylogenies of rRNA and actin or polyubiquitin. They are the natural predators of many species of microbacteria and Archea.

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 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

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

Filose (subphylum Filosa)

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)

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. Filosa is apparently a monophyletic group, but Endomyxa is paraphyletic.

Ungrouped

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

Classification

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

Phylogeny based on Bass et al. 2009, Howe etal. 2011 and Silar 2016. In 2019, Cercozoa were recognized as sister to Retaria in Rhizaria.

Taxonomy

Phylum Cercozoa * Family ?Gymnophrydiidae * Family ?Gymnophryidae Mikrjukov & Mylnikov 1996 * Family ?Rhizoplasmidae Cavalier-Smith & Bass 2009 * Order ?Gymnosphaerida Poche 1913 emend. Mikrjukov 2000 xoplasthelida** Family Gymnosphaeridae Poche 1913 edraiophryidae; Gymnidae; Wagnerellidae Poche 1913* Clade Marimyxia Cavalier-Smith 2017 ** Order Reticulosida Cavalier-Smith 2003 emend. Bass et al. 2009 *** Family Filoretidae Cavalier-Smith & Bass 2009 ** Class Gromiidea Cavalier-Smith 2003 *** Order Gromiida Claparède & Lachmann 1856 s.s. ** Class Ascetosporea Desportes & Ginsburger-Vogel, 1977 emend. Cavalier-Smith 2009 plosporidies 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 aramyxea 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] ** Order [[Phagomyxida Cavalier-Smith 1993 ** Order Plasmodiophorida Cook 1928 em. Cavalier-Smith 1993 * Class Vampyrellidea Cavalier-Smith 2017 ristivesiculatia Page 1987 stat. nov. Cavalier-Smith 1993** Order Vampyrellida West 1901 emend. Hess et al. 2012 conchulinida de Saedeleer 1934 emend. Bass et al. 2009; Cristivesiculatida Page 1987 * Subphylum Filosa Leidy 1879 emend. Cavalier-Smith 2003 ** Class Skiomonadea Cavalier-Smith 2012 *** Order Tremulida Cavalier-Smith & Howe 2011 ** Class Chlorarachnea Hibberd & Norris 1984 hlorarachniophyceae Hibberd & Norris 1984; Chlorarachniophyta Hibberd & Norris 1984; Chlorarachnia Cavalier-Smith 1993*** Order Minorisida Cavalier-Smith 2017 *** Order Chlorarachniida Hibberd & Norris 1984 hlorarachniales; Chlorarachniophida** Class Granofilosea Cavalier-Smith & Bass 2009 *** Family ?Microgromiidae De Saedeleer 1934 *** Order ?Axomonadida xonucleoaxoplastiales*** Order Desmothoracida Honigberg et al. 1964 ryptaxohelida; Desmothoraca Hertwig & Lesser 1874*** Order Cryptofilida Cavalier-Smith & Bass 2009 *** Order Limnofilida Cavalier-Smith & Bass 2009 *** Order Leucodictyida Cavalier-Smith 1993 emend. 2003 ** Infraphylum Monadofilosa Cavalier-Smith 1997 oglissa Cavalier-Smiths 2012*** Family ?Katabiidae Cavalier-Smith 2012 *** Family ?Krakenidae Dumack, Mylnikov & Bonkowski 2017 *** Order ?Pseudodimorphida *** Class Helkesea Cavalier-Smith 2017 **** Order Ventricleftida Cavalier-Smith 2011 **** Order Helkesida Cavalier-Smith 2017 ainourida*** Order Cercomonadida Poche 1913 emend. Karpov et al. 2006 *** Class Metromonadea Cavalier-Smith 2007 s.s. **** Order Metromonadida Bass & Cavalier-Smith 2004 **** Order Metopiida Cavalier-Smith 2003 *** Clade Glissomonadida-Pansomonadida **** Order Glissomonadida Howe & Cavalier-Smith 2009 emend. Hess et al. 2013 **** Order Pseudosporida Hibberd 1983 sensu Cavalier-Smith 1993 **** Order Dimorphida Siemensma 1991 ndonucleoplastiales**** Order Pansomonadida Vickerman 2005 *** Class Silicofilosea Adl et al. 2005 emend. Adl et al. 2012 mbricatea Cavalier-Smith 2011**** Order Perlofilida Cavalier-Smith 2012 **** Order Spongomonadida Hibberd 1983 emend. Karpov 1990 **** Order Zoelucasida Cavalier-Smith 2014 **** Order Rotosphaerida Rainer 1968 **** Order Thaumatomonadida Shirkina 1987 **** Order Discocelida Cavalier-Smith 1997 **** Order Discomonadida **** Order Variglissida **** Order Marimonadida Cavalier-Smith & Bass 2011 uranticordida**** Order Euglyphida Copeland 1956 emend. Cavalier-Smith 1997 uglyphina Bovee 1985*** Class Thecofilosea Cavalier-Smith 2003 emend. Cavalier-Smith 2011 ripylea Hertwig 1879**** Order Hemimastigida Foissner, Blatterer & Foissner 1988 emimastigophora Foissner, Blatterer & Foissner 1988 sensu Cavalier-Smith 1993; Hemimastigea Foissner, Blatterer & Foissner 1988; Hemimastigidea **** Order Matazida Cavalier-Smith 2012 **** Order Ebriida Poche [Ebriidea Lemmermann 1901 emend. Deflandre 1936; Ebiophyta; Ebriacea Lemmermann 1901; Ebriophyceae Loeblich 1970; Ebriales Honigsberg 1964; Stereotestales] **** Order [[Cryomonadida Cavalier-Smith 1993 [Cryothecomonadea; Cryothecomonadida] **** Order [[Tectofilosida **** Order [[Eodarida Cavalier-Smith 2012 haeodinia**** Order Opaloconchida Cavalier-Smith 2012 File:Cercomonas sp.jpg|''Cercomonas'' sp. (Cercozoa: Cercomonadida File:Ebria_tripartita.jpg|''Ebria'' sp. (Cercozoa: Ebridea) File:Rhipidodendron splendidum.jpg|''Rhipidodendron'' sp. (Cercozoa: Spongomonadea) File:Euglypha_sp.jpg|''Euglypha'' sp. (Cercozoa: Euglyphida) File:Haeckel Phaeodaria 1.jpg|Phaeodarians (Cercozoa: Phaeodarea) File:Clathrulina elegans - - Print - Iconographia Zoologica - Special Collections University of Amsterdam - UBAINV0274 113 04 0030.tif|''Clathrulina elegans'' (Cercozoa: Granofilosea: Desmothoracida) File:Chlorarachnion_reptans.jpg|''Chlorarachnion'' sp. (Cercozoa: (Chlorarachniophyta) File:Vampyrella lateritia.jpg|''Vampyrella'' sp. (Cercozoa: Vampyrellidae) File:Die_Gartenlaube_(1890)_b_083.jpg|''Gromia'' (Cercozoa: Gromiidea) File:Powdery scab (Spongospora subterranea) of potatoes (1914) (14577838889).jpg|Powdery scab (Cercozoa: Plasmodiophorida) Recently an orphan protist Quadricilia rotundata finally finds fts phylogenetic home in Cercozoa.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

References



External links


Tree of Life
Cercozoa
phylogeny of Phaeodarea
{{Taxonbar|from=Q500497 Category:SAR supergroup phyla Category:Taxa named by Thomas Cavalier-Smith