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Choanoflagellate
| Choanoflagellates Temporal range: Neoproterozoic-present, fossils from Only possible fossils are known from Cretaceous (Cenomanian/Turonian)[1][2]
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|---|---|
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| Codosiga sp. | |
Scientific classification 
| |
| Domain: | Eukaryota |
| Clade: | Amorphea |
| Clade: | Obazoa |
| (unranked): | Opisthokonta |
| (unranked): | Holozoa |
| (unranked): | Filozoa |
| Clade: | Choanozoa |
| Class: | Choanoflagellata Kent, 1880–1882[3][4] |
| Type species | |
| Monosiga brevicollis[5] | |
| Orders & families | |
| Synonyms | |
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Choanoflagellates are a group of free-living unicellular and colonial flagellate eukaryotes considered to be the closest living relatives of animals. The name refers to the characteristic funnel-shaped "collar" of interconnected microvilli and the presence of a flagellum. Choanoflagellates are found globally in aquatic environments, and they are of particular interest to evolutionary biologists studying the origins of multicellularity in animals.
The flagellum of choanoflagellates is surrounded by microvilli at its base. Movement of the flagellum creates water currents that can propel free-swimming choanoflagellates through the water column and trap bacteria and detritus against the microvilli, where these foodstuffs are engulfed. This feeding plays an ecological role in the carbon cycle by linking different trophic levels.
Choanoflagellates bear morphological similarities to the choanocyte, a type of cell in sponges, and this provided an early clue to their close relationship with animals, which was later upheld by genetic analyses. As the sister group to Animalia, choanoflagellates serve as a useful model for reconstructions of the last unicellular ancestor of animals. According to a 2021 study, crown group craspedids (and perhaps crown group choanoflagellates if Acanthoecida arose within Craspedida[9]) appeared 422.78 million years ago,[10] Although a previous study from 2017 recovered the divergence of the crown group choanoflagellates (craspedids) at 786.62 million years.[11]
- ^ Fonseca, Carolina; Mendonça Filho, João Graciano; Reolid, Matías; Duarte, Luís V.; de Oliveira, António Donizeti; Souza, Jaqueline Torres; Lézin, Carine (2023-01-23). "First putative occurrence in the fossil record of choanoflagellates, the sister group of Metazoa". Scientific Reports. 13 (1): 1242. Bibcode:2023NatSR..13.1242F. doi:10.1038/s41598-022-26972-8. ISSN 2045-2322. PMC 9870899. PMID 36690681.
- ^ Parfrey LW, Lahr DJ, Knoll AH, Katz LA (August 2011). "Estimating the timing of early eukaryotic diversification with multigene molecular clocks". Proceedings of the National Academy of Sciences of the United States of America. 108 (33): 13624–9. Bibcode:2011PNAS..10813624P. doi:10.1073/pnas.1110633108. PMC 3158185. PMID 21810989.
- ^ Saville-Kent, W. (1880). A manual of Infusoria. London, vol. 1, p. 324, [1].
- ^ Adl SM, Bass D, Lane CE, Lukeš J, Schoch CL, Smirnov A, Agatha S, Berney C, Brown MW, Burki F, Cárdenas P, Čepička I, Chistyakova L, del Campo J, Dunthorn M, Edvardsen B, Eglit Y, Guillou L, Hampl V, Heiss AA, Hoppenrath M, James TY, Karnkowska A, Karpov S, Kim E, Kolisko M, Kudryavtsev A, Lahr DJG, Lara E, Le Gall L, Lynn DH, Mann DG, Massana R, Mitchell EAD, Morrow C, Park JS, Pawlowski JW, Powell MJ, Richter DJ, Rueckert S, Shadwick L, Shimano S, Spiegel FW, Torruella G, Youssef N, Zlatogursky V, Zhang Q (2019). "Revisions to the Classification, Nomenclature, and Diversity of Eukaryotes". Journal of Eukaryotic Microbiology. 66 (1): 4–119. doi:10.1111/jeu.12691. PMC 6492006. PMID 30257078.
- ^ King N, Westbrook MJ, Young SL, Kuo A, Abedin M, Chapman J, et al. (February 2008). "The genome of the choanoflagellate Monosiga brevicollis and the origin of metazoans". Nature. 451 (7180): 783–8. Bibcode:2008Natur.451..783K. doi:10.1038/nature06617. PMC 2562698. PMID 18273011.
- ^ Nitsche F, Carr M, Arndt H, Leadbeater BS (2011). "Higher level taxonomy and molecular phylogenetics of the Choanoflagellatea". The Journal of Eukaryotic Microbiology. 58 (5): 452–62. doi:10.1111/j.1550-7408.2011.00572.x. PMID 21895836. S2CID 2076733.
- ^ Cavalier-Smith T (1998). "Neomonada and the origin of animals and fungi.". In Coombs GH, Vickerman K, Sleigh MA, Warren A (eds.). Evolutionary relationships among protozoa. London: Kluwer. pp. 375–407.
- ^ Leadbeater BS (2015). The choanoflagellates: evolution, biology, and ecology. University of Birmingham. ISBN 978-0-521-88444-0.
- ^ Carr, Martin; Leadbeater, Barry S. C. (2022-12-01). "Re-evaluating Loricate Choanoflagellate Phylogenetics: Molecular Evidence Points to the Paraphyly of Tectiform Species". Protist. 173 (6): 125924. doi:10.1016/j.protis.2022.125924. ISSN 1434-4610.
- ^ Schiwitza, Sabine; Gutsche, Lennart; Freches, Eric; Arndt, Hartmut; Nitsche, Frank (2021-06-01). "Extended divergence estimates and species descriptions of new craspedid choanoflagellates from the Atacama Desert, Northern Chile". European Journal of Protistology. 79: 125798. doi:10.1016/j.ejop.2021.125798. ISSN 0932-4739.
- ^ Dohrmann, Martin; Wörheide, Gert (2017-06-15). "Dating early animal evolution using phylogenomic data". Scientific Reports. 7 (1): 3599. doi:10.1038/s41598-017-03791-w. ISSN 2045-2322. PMC 5472626.
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