Opisthokont (Redirected from Opisthokonts)

Opisthokont
Temporal range: 1300 –0 Ma
Clockwise, from top left: Abeoforma whisleri (Mesomycetozoea); Amanita muscaria (Fungi); Desmarella moniliformis (Choanoflagellatea); bonnet macaque (Metazoa); Nuclearia thermophila (Nucleariida); Ministeria vibrans (Filasterea)
Scientific classification
Domain: Eukaryota
Clade: Amorphea
Clade: Obazoa
(unranked): Opisthokonta
Copeland 1956, emend. Cavalier-Smith 1987, emend. Adl et al., 2005
Subgroups

The opisthokonts (from Ancient Greek ὀπίσθιος (opísthios) 'rear, posterior', and κοντός (kontós) 'pole, i.e. flagellum') are a broad group of eukaryotes, including both the animal and fungus kingdoms. The opisthokonts, previously called the "Fungi/Metazoa group", are generally recognized as a clade. Opisthokonts together with Apusomonadida and Breviata comprise the larger clade Obazoa.

Flagella and other characteristics

A common characteristic of opisthokonts is that flagellate cells, such as the sperm of most animals and the spores of the chytrid fungi, propel themselves with a single posterior flagellum. It is this feature that gives the group its name. In contrast, flagellate cells in other eukaryote groups propel themselves with one or more anterior flagella. However, in some opisthokont groups, including most of the fungi, flagellate cells have been lost.

Opisthokont characteristics include synthesis of extracellular chitin in exoskeleton, cyst/spore wall, or cell wall of filamentous growth and hyphae; the extracellular digestion of substrates with osmotrophic absorption of nutrients; and other cell biosynthetic and metabolic pathways. Genera at the base of each clade are amoeboid and phagotrophic.

History

The close relationship between animals and fungi was suggested by Thomas Cavalier-Smith in 1987, who used the informal name opisthokonta (the formal name has been used for the chytrids by Copeland in 1956), and was supported by later genetic studies.

Early phylogenies placed fungi near the plants and other groups that have mitochondria with flat cristae, but this character varies. More recently, it has been said that holozoa (animals) and holomycota (fungi) are much more closely related to each other than either is to plants, because opisthokonts have a triple fusion of carbamoyl phosphate synthetase, dihydroorotase, and aspartate carbamoyltransferase that is not present in plants, and plants have a fusion of thymidylate synthase and dihydrofolate reductase not present in the opisthokonts. Animals and fungi are also more closely related to amoebas than to plants, and plants are more closely related to the SAR supergroup of protists than to animals or fungi.[citation needed] Animals and fungi are both heterotrophs, unlike plants, and while fungi are sessile like plants, there are also sessile animals.

Cavalier-Smith and Stechmann argue that the uniciliate eukaryotes such as opisthokonts and Amoebozoa, collectively called unikonts, split off from the other biciliate eukaryotes, called bikonts, shortly after they evolved.

Taxonomy

Opisthokonts are divided into Holomycota or Nucletmycea (fungi and all organisms more closely related to fungi than to animals) and Holozoa (animals and all organisms more closely related to animals than to fungi); no opisthokonts basal to the Holomycota/Holozoa split have yet been identified.[citation needed] The Opisthokonts was largely resolved by Torriella et al. Holomycota and Holozoa are composed of the following groups.[citation needed]

Phylogeny

The following phylogenetic tree indicates the evolutionary relationships between the different opisthokont lineages, and the time divergence of the clades in millions of years ago (Mya).

Amorphea

Amoebozoa

Obazoa

Breviatea

Apusomonadida

Opisthokonta
Holomycota

Nucleariae

Fungi
Phytophagea

True Fungi

410 Mya

Aphelida

Opisthophagea

Rozellida

Microsporidia

sensu lato
Holozoa

Ichthyosporea

Pluriformea

Corallochytrium

Syssomonas

Tunicaraptor

Filozoa

Filasterea

Choanozoa

Choanoflagellatea

Metazoa

760 Mya
950 mya
1300 Mya
1500 Mya

Gallery


This page was last updated at 2024-02-17 10:01 UTC. Update now. View original page.

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