• Source: Metamonad

The metamonads are a large group of flagellate amitochondriate microscopic eukaryotes. They include the retortamonads, diplomonads, parabasalids, oxymonads, and a range of more poorly studied taxa, most of which are free-living flagellates. All metamonads are anaerobic (many being aerotolerant anaerobes), and most members of the four groups listed above are symbiotes or parasites of animals, as is the case with Giardia lamblia which causes diarrhea in mammals.




Characteristics


A number of parabasalids and oxymonads are found in termite guts, and play an important role in breaking down the cellulose found in wood. Some other metamonads are parasites.
These flagellates are unusual in lacking aerobic mitochondria. Originally they were considered among the most primitive eukaryotes, diverging from the others before mitochondria appeared. However, they are now known to have lost aerobic mitochondria secondarily, and retain both organelles and nuclear genes derived ultimately from the mitochondrial endosymbiont genome. Mitochondrial relics include hydrogenosomes, which produce hydrogen (and make ATP), and small structures called mitosomes.
It now appears the Metamonada are, together with Malawimonas, sister clades of the Podiata.
All of these groups have flagella or basal bodies in characteristic groups of four (or more, in parabasalids), which are often associated with the nucleus, forming a structure called a karyomastigont. In addition, genera such as Carpediemonas and Trimastix are now known to be close relatives of the retortamonad-diplomonad lineage and the oxymonads, respectively. Most of the closer relatives of the retortamonad-diplomonad lineage actually have two flagella and basal bodies.




Classification


The metamonads were thought to make up part of the Excavata, a proposed eukaryotic supergroup including flagellates with feeding grooves and their close relatives. Their relationships are uncertain, and they do not always appear together on molecular trees. Current opinion is that Excavata is not a monophyletic group, but it might be paraphyletic.
The following higher level treatment from 2013 is based on works of Cavalier-Smith with amendments within Fornicata from Yubuki, Simpson & Leander.
Metamonada were once again proposed to be basal eukaryotes in 2018.

Phylum Metamonada (Grassé 1952) Cavalier-Smith 1987 emend. Cavalier-Smith 2003
Family Anaeramoebidae Táborský, Pánek & Čepička 2017
Subphylum Anaeromonada Cavalier-Smith 1997 emend. 2003
Class Anaeromonadea Cavalier-Smith 1997 emend. 1999
Family Paratrimastigidae Zhang et al. 2015
Order Trimastigida Cavalier-Smith 2003
Family Trimastigidae Saville Kent 1880
Order Oxymonadida Grassé 1952 emend. Cavalier-Smith 2003
Family Polymastigidae Bütschli 1884
Family Saccinobaculidae Brugerolle & Lee 2002 ex Cavalier-Smith 2013
Family Pyrsonymphidae Grassé 1892
Family Oxymonadidae Kirby 1928
Subphylum Trichozoa Cavalier-Smith 1996 emend. Cavalier-Smith 2003 stat. n. 2013
Superclass Fornicata Simpson 2003 stat. n. Cavalier-Smith 2013
Family Kipferliidae Cavalier-Smith 2013
Class Carpediemonadea Cavalier-Smith 2013 s.s.
Order Carpediemonadida Cavalier-Smith 2003 emend. 2013 s.s.
Family Carpediemonadidae Cavalier-Smith 2003
Class Eopharyngea Cavalier-Smith 1993 stat. n. Cavalier-Smith 2003
Order Dysnectida Cavalier-Smith 2013
Family Dysnectidae Cavalier-Smith 2013
Order Retortamonadida Grassé 1952 emend. Cavalier-Smith 2013
Family Caviomonadidae Cavalier-Smith 2013
Family Chilomastigidae Cavalier-Smith 2013
Family Retortamonadidae Wenrich 1932
Order Diplomonadida Wenyon 1926 emend. Brugerolle et al. 1975
Family Giardiidae Kulda & Nohy´nkova´ 1978
Family Octomitidae Cavalier-Smith 1996
Family Spironucleidae Cavalier-Smith 1996
Family Hexamitidae Kent 1880 emend. Brugerolle et al. 1975
Superclass Parabasalia Honigberg 1973 stat. n. Cavalier-Smith 2003
Class Trichonymphea Cavalier-Smith 2003
Order Lophomonadida Light 1927
Family Lophomonadidae Saville Kent 1880
Order Trichonymphida Poche 1913
Family †Burmanymphidae Poinar 2009
Family Retractinymphidae Radek & Brune 2023
Family Spirotrichosomidae Hollande & Caruette-Valentin 1971
Family Staurojoeninidae Grassé 1917
Family Trichonymphidae Saville Kent 1880
Family Hoplonymphidae Light 1926
Family Teratonymphidae Koidzumi 1921 [Eucomonymphidae]
Class Trichomonadea Kirby 1947 stat. n. Cavalier-Smith 2003
Order Pimpavickida Céza & Čepička 2022
Family Pimpavickidae Céza & Čepička 2022
Order Trichomonadida Kirby 1947
Family Lacusteriidae Céza & Čepička 2022
Family Trichomonadidae Chalmers & Pekkoloa 1918 sensu Hampl et al. 2006
Order Honigbergiellida Čepička et al. 2010
Family Honigbergiellidae Čepička, Hampl & Kulda 2010
Family Hexamastigidae Čepička, Hampl & Kulda 2010
Family Tricercomitidae Čepička, Hampl & Kulda 2010
Order Hypotrichomonadida Čepička et al. 2010
Family Hypotrichomonadidae (Honigberg 1963) Čepička, Hampl & Kulda 2010
Order Spirotrichonymphida Grassé 1952
Family Spirotrichonymphidae Grassé 1917
Order Tritrichomonadida Čepička et al. 2010
Family Dientamoebidae Grassé 1953
Family Monocercomonadidae Kirby 1944
Family Simplicimonadidae Čepička et al. 2010
Family Tritrichomonadidae Honigberg 1963
Order Cristamonadida Brugerolle & Patterson 2001 emend. Cavalier-Smith 2013
Family Calonymphidae Grassé 1911
Family Devescovinidae Doflein 1911




Evolution


Within Metamonada, two main branches are recovered in recent phylogenetic analyses. One branch contains the Parabasalia and the closely related anaeramoebae. The other branch contains two large groups: the Fornicata, which is closely related to barthelonids and the recently isolated Skoliomonas; and the Preaxostyla.




References






= Citations

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= Cited literature

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External links


Tree of Life: Fornicata

Kata Kunci Pencarian:

• Metamonada
• Euglena
• Trypanosoma
• Trichomonas vaginalis
• Trichomonas
• Naegleria
• Mixotricha paradoxa
• Malawimonad
• Euglenozoa
• Excavata
• Metamonad
• Excavata
• Mitochondrion
• Eukaryote
• Diplomonad
• Protist
• Phylum
• Henneguya zschokkei
• List of pathogens by size
• Parabasalid