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| Metamonads
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Giardia lamblia, a parasitic diplomonad | ||||
| Scientific classification | ||||
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| Classes & orders | ||||
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Eopharyngia Retortamonad ida Diplomonadida Carpediemonas Parabasalia Anaeromonada |
Originally these flagellates were considered to have diverged from other eukaryotes before mitochondria appeared, along with a few other lines ( pelobionts, entamoebae, and microsporidia ). Cavalier-Smith proposed a separate kingdom Archezoa for such forms. However, all are now known to have lost mitochondria secondarily, and metamonads retain both organelles and nuclear genes derived from them. Mitochondrial relics include hydrogenosome s, which produce hydrogen, and small structures called mitosome s.
In addition to these groups, the genera Carpediemonas and Trimastix are now known to be close relatives of the retortamonad-diplomonad line and oxymonads, respectively. All of these belong among the excavates, a group of flagellates that have feeding grooves or are closely related to such forms. Their relationships are still being worked out, and it is possible the organisms listed here do not make up a monophyletic subgroup. However, they are linked by having flagellaThe flagellum (plural: flagella is a propulsive structure used by many single-celled organisms to move through a liquid medium. There are three main varieties of flagellum; the bacterial flagellum (a helical filament that rotates like a screw), archaeal f or at least basal bodies in characteristic groups of four, often associated with the nucleusIn cell biology, the nucleus is an organelle, found in most eukaryotic cells, which contains most of the cell's genetic material. Nuclei have two primary functions: to control chemical reactions within the cytoplasm and to store information needed for cel in a structure called a karyomastigont.