Biology:Amorphea

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Short description: Members of the Unikonta, a taxonomic group proposed by Thomas Cavalier-Smith

Amorphea
Temporal range: Early Ectasian - Present, 1400–0 Ma

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Scientific classification e
Domain: Eukaryota
Clade: Amorphea
Adl et al., 2012[1]
Subgroups
Synonyms

Amorphea[1] is a taxonomic supergroup that includes the basal Amoebozoa and Obazoa. That latter contains the Opisthokonta, which includes the Fungi, Animals and the Choanomonada, or Choanoflagellates. The taxonomic affinities of the members of this clade were originally described and proposed by Thomas Cavalier-Smith in 2002.[2][4]

The International Society of Protistologists, the recognised body for taxonomy of protozoa, recommended in 2012 that the term Unikont be changed to Amorphea because the name "Unikont" is based on a hypothesized synapomorphy that the ISOP authors and other scientists later rejected.[1][5]

It includes amoebozoa, opisthokonts,[6][7] and Apusomonada.[8]

Taxonomic revisions within this group

Thomas Cavalier-Smith proposed two new phyla: Sulcozoa, which consists of the subphyla Apusozoa (Apusomonadida and Breviatea), and Varisulca, which includes the subphyla Diphyllatea, Discocelida, Mantamonadidae, Planomonadida and Rigifilida.[9]

Further work by Cavalier-Smith showed that Sulcozoa is paraphyletic.[10] Apusozoa also appears to be paraphyletic. Varisulca has been redefined to include planomonads, Mantamonas and Collodictyon. A new taxon has been created - Glissodiscea - for the planomonads and Mantamonas. Again, the validity of this revised taxonomy awaits confirmation.

Amoebozoa seems to be monophyletic with two major branches: Conosa and Lobosa. Conosa is divided into the aerobic infraphylum Semiconosia (Mycetozoa and Variosea) and secondarily anaerobic Archamoebae. Lobosa consists entirely of non-flagellated lobose amoebae and has been divided into two classes: Discosea, which have flattened cells, and Tubulinea, which has predominantly tube-shaped pseudopodia.[11]

Clade

The group includes eukaryotic cells that, for the most part, have a single emergent flagellum, or are amoebae with no flagella. The unikonts include opisthokonts (animals, fungi, and related forms) and Amoebozoa. By contrast, other well-known eukaryotic groups, which more often have two emergent flagella (although there are many exceptions), are often referred to as bikonts. Bikonts include Archaeplastida (plants and relatives) and SAR supergroup, the Cryptista, Haptista, Telonemia and picozoa.

Characteristics

The unikonts have a triple-gene fusion that is lacking in the bikonts. The three genes that are fused together in the unikonts, but not bacteria or bikonts, encode enzymes for synthesis of the pyrimidine nucleotides: carbamoyl phosphate synthase, dihydroorotase, aspartate carbamoyltransferase. This must have involved a double fusion, a rare pair of events, supporting the shared ancestry of Opisthokonta and Amoebozoa.

Cavalier-Smith[2] originally proposed that unikonts ancestrally had a single flagellum and single basal body. This is unlikely, however, as flagellated opisthokonts, as well as some flagellated Amoebozoa, including Breviata, actually have two basal bodies, as in typical 'bikonts' (even though only one is flagellated in most unikonts). This paired arrangement can also be seen in the organization of centrioles in typical animal cells. In spite of the name of the group, the common ancestor of all 'unikonts' was probably a cell with two basal bodies.

References

  1. ↑ 1.0 1.1 1.2 "The revised classification of eukaryotes". J Eukaryot Microbiol 59 (5): 429–93. September 2012. doi:10.1111/j.1550-7408.2012.00644.x. PMID 23020233. 
  2. ↑ 2.0 2.1 2.2 Cavalier-Smith T (March 2002). "The phagotrophic origin of eukaryotes and phylogenetic classification of Protozoa". Int. J. Syst. Evol. Microbiol. 52 (Pt 2): 297–354. doi:10.1099/00207713-52-2-297. PMID 11931142. http://ijs.sgmjournals.org/cgi/pmidlookup?view=long&pmid=11931142. 
  3. ↑ Derelle, Romain; Torruella, Guifré; Klimeš, Vladimír; Brinkmann, Henner; Kim, Eunsoo; Vlček, Čestmír; Lang, B. Franz; Eliáš, Marek (17 February 2015). "Bacterial proteins pinpoint a single eukaryotic root" (in en). Proceedings of the National Academy of Sciences 112 (7): E693–E699. doi:10.1073/pnas.1420657112. PMID 25646484. Bibcode: 2015PNAS..112E.693D. 
  4. ↑ Cavalier-Smith, Thomas (2003). "Protist phylogeny and the high-level classification of Protozoa". European Journal of Protistology 39 (4): 338–348. doi:10.1078/0932-4739-00002. 
  5. ↑ "Evolution: revisiting the root of the eukaryote tree". Current Biology 19 (4): R165–R167. 2009. doi:10.1016/j.cub.2008.12.032. PMID 19243692. 
  6. ↑ "Evolutionary position of breviate amoebae and the primary eukaryote divergence". Proc. Biol. Sci. 276 (1657): 597–604. November 2008. doi:10.1098/rspb.2008.1358. PMID 19004754. 
  7. ↑ "Monophyly of Rhizaria and multigene phylogeny of unicellular bikonts". Mol. Biol. Evol. 23 (10): 1922–30. October 2006. doi:10.1093/molbev/msl055. PMID 16829542. 
  8. ↑ Burki, Fabien; Roger, Andrew J.; Brown, Matthew W.; Simpson, Alastair G. B. (2020-01-01). "The New Tree of Eukaryotes". Trends in Ecology & Evolution 35 (1): 43–55. doi:10.1016/j.tree.2019.08.008. ISSN 0169-5347. PMID 31606140. 
  9. ↑ Cavalier-Smith T (May 2013). "Early evolution of eukaryote feeding modes, cell structural diversity, and classification of the protozoan phyla Loukozoa, Sulcozoa, and Choanozoa". Eur J Protistol 49 (2): 115–78. doi:10.1016/j.ejop.2012.06.001. PMID 23085100. 
  10. ↑ "Multigene eukaryote phylogeny reveals the likely protozoan ancestors of opisthokonts (animals, fungi, choanozoans) and Amoebozoa". Mol Phylogenet Evol 81: 71–85. December 2014. doi:10.1016/j.ympev.2014.08.012. PMID 25152275. 
  11. ↑ "Multigene phylogeny resolves deep branching of Amoebozoa". Mol Phylogenet Evol 83: 293–304. February 2015. doi:10.1016/j.ympev.2014.08.011. PMID 25150787. 

External links

Wikidata ☰ Q474156 entry



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