Amorphea
| Unikonts | |
|---|---|
| |
| Orange elephant ear sponge, Agelas clathrodes, in foreground. Two corals in the background: a sea fan, Iciligorgia schrammi, and a sea rod, Plexaurella nutans. | |
| Scientific classification | |
| Domain: | |
| (unranked) | Unikonta |
| Supergroups | |
Unikonts are members of the Unikonta, a taxonomic group proposed by Thomas Cavalier-Smith.[1][2]
It includes amoebozoa, opisthokonts,[3][4] and possibly Apusozoa.[5]
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), Excavata, Rhizaria, and Chromalveolata.
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 [1] 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
- ^ a b Cavalier-Smith T (2002). "The phagotrophic origin of eukaryotes and phylogenetic classification of Protozoa". Int. J. Syst. Evol. Microbiol. 52 (Pt 2): 297–354. PMID 11931142.
{{cite journal}}: Unknown parameter|month=ignored (help) - ^ 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.
- ^ A Minge M, Silberman JD, Orr RJ; et al. (2008). "Evolutionary position of breviate amoebae and the primary eukaryote divergence". Proc. Biol. Sci. 276 (1657): 597–604. doi:10.1098/rspb.2008.1358. PMC 2660946. PMID 19004754.
{{cite journal}}: Explicit use of et al. in:|author=(help); Unknown parameter|month=ignored (help)CS1 maint: multiple names: authors list (link) - ^ Burki F, Pawlowski J (2006). "Monophyly of Rhizaria and multigene phylogeny of unicellular bikonts". Mol. Biol. Evol. 23 (10): 1922–30. doi:10.1093/molbev/msl055. PMID 16829542.
{{cite journal}}: Unknown parameter|month=ignored (help) - ^ Glücksman E, Snell EA, Berney C, Chao EE, Bass D, Cavalier-Smith T (2010). "The Novel Marine Gliding Zooflagellate Genus Mantamonas (Mantamonadida ord. n.: Apusozoa)". Protist. 162 (2): 207–221. doi:10.1016/j.protis.2010.06.004. PMID 20884290.
{{cite journal}}: Unknown parameter|month=ignored (help)CS1 maint: multiple names: authors list (link)
External links
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