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Two Euglena.jpg
Two Euglena
Scientific classification

Classes and unplaced genera


  • Euglenoida Cavalier-Smith, 1978

The euglenozoa are a large group of flagellate Excavata. They include a variety of common free-living species, as well as a few important parasites, some of which infect humans. There are two main subgroups, the euglenids and kinetoplastids. Euglenozoa are unicellular, mostly around 15-40 µm in size, although some euglenids get up to 500 µm long.[2]


Most euglenozoa have two flagella, which are inserted parallel to one another in an apical or subapical pocket. In some these are associated with a cytostome or mouth, used to ingest bacteria or other small organisms. This is supported by one of three sets of microtubules that arise from the flagellar bases; the other two support the dorsal and ventral surfaces of the cell.[3]

Some other euglenozoa feed through absorption, and many euglenids possess chloroplasts, the only eukaryotes outside Diaphoretickes to do so without performing kleptoplasty,[4] and so obtain energy through photosynthesis. These chloroplasts are surrounded by three membranes and contain chlorophylls A and B, along with other pigments, so are probably derived from a captured green alga. Reproduction occurs exclusively through cell division. During mitosis, the nuclear membrane remains intact, and the spindle microtubules form inside of it.[3]

The group is characterized by the ultrastructure of the flagella. In addition to the normal supporting microtubules or axoneme, each contains a rod (called paraxonemal), which has a tubular structure in one flagellum and a latticed structure in the other. Based on this, two smaller groups have been included here: the diplonemids and Postgaardi.[5]


The euglenozoa are generally accepted as monophyletic. They are related to Percolozoa; the two share mitochondria with disk-shaped cristae, which only occurs in a few other groups.[6] Both probably belong to a larger group of eukaryotes called the Excavata.[7] This grouping, though, has been challenged.[8]


The phylogeny based on the work of Cavalier-Smith 2016.[9]


Phylum Euglenozoa Cavalier-Smith 1981 emend. Simpson 1997[9][10] [Euglenobionta]

  • Subphylum Glycomonada Cavalier-Smith 2016
  • Subphylum Plicomonada Cavalier-Smith 2017
    • Infraphylum Postgaardia Cavalier-Smith 2016 stat. nov. Cavalier-Smith 2017
    • Infraphylum Euglenoida Bütschli 1884 emend. Senn 1900 stat. nov. Cavalier-Smith, 2017 [Euglenophyta; Euglenida Buetschli 1884; Euglenoidina Buetschli 1884]
      • Parvphylum Entosiphona Cavalier-Smith 2016 stat. nov. Cavalier-Smith 2017
      • Parvphylum Dipilida Cavalier-Smith 2016 stat. nov. Cavalier-Smith 2017
        • Class Stavomonadea Cavalier-Smith 2016 [Petalomonadea Cavalier-Smith 1993; Petalomonadophyceae]
        • Class Ploeotarea Cavalier-Smith 2016
        • Superclass Spirocuta Cavalier-Smith 2016
          • Class Peranemea Cavalier-Smith 1993 emend. Cavalier-Smith 2016
            • Subclass Acroglissia Cavalier-Smith 2016
            • Subclass Peranemia Cavalier-Smith 2016
              • Order Peranemida Bütschli 1884 stat. nov. Cavalier-Smith 1993
                • Family Peranematidae [Peranemataceae Dujardin 1841; Pseudoperanemataceae Christen 1962]
            • Subclass Anisonemia Cavalier-Smith 2016
              • Order Anisonemida Cavalier-Smith 2016 [Heteronematales Leedale 1967]
                • Family Anisonemidae Saville Kent, 1880 em. Cavalier-Smith 2016 [Heteronemidae Calkins 1926; Zygoselmidaceae Kent 188]
              • Order Natomonadida Cavalier-Smith 2016
                • Suborder Metanemina Cavalier-Smith 2016
                • Suborder Rhabdomonadina Leedale 1967 emend. Cavalier-Smith 1993 [Astasida Ehrenberg 1831; Rhabdomonadia Cavalier-Smith 1993; Rhabdomonadophyceae; Rhabdomonadales]
                  • Family Distigmidae Hollande, 1942
                  • Family Astasiidae Saville Kent, 1884 [Astasiaceae Ehrenberg orth. mut. Senn 1900; Rhabdomonadaceae Fott 1971; Menoidiaceae Buetschli 188; Menoidiidae Hollande, 1942]
          • Class Euglenophyceae Schoenichen 1925 emend. Marin & Melkonian 2003 [Euglenea Bütschli 1884 emend. Busse & Preisfeld 2002; Euglenoidea Bütschli 1884; Euglenida Bütschli 1884] (Photosynthetic clade)
            • Subclass Rapazia Cavalier-Smith 2016
            • Subclass Euglenophycidae Busse and Preisfeld, 2003
              • Order Eutreptiida [Eutreptiales Leedale 1967 emend. Marin & Melkonian 2003; Eutreptiina Leedale 1967]
              • Order Euglenida Ritter von Stein, 1878 stat. n. Calkins, 1926 [Euglenales Engler 1898 emend. Marin & Melkonian 2003; Euglenina Buetschli 1884; Euglenomorphales Leedale 1967; Colaciales Smith 1938]
                • Family Euglenamorphidae Hollande, 1952 stat. n. Cavalier-Smith 2016 [Euglenomorphaceae; Hegneriaceae Brumpt & Lavier 1924]
                • Family Phacidae [Phacaceae Kim et al. 2010]
                • Family Euglenidae Bütschli 1884 [Euglenaceae Dujardin 1841 emend. Kim et al. 2010; Colaciaceae Smith 1933] (Mucilaginous clade)


  1. ^ T. Cavalier-Smith (1981). "Eukaryote Kingdoms: Seven or Nine?". BioSystems. 14 (3–4): 461–481. doi:10.1016/0303-2647(81)90050-2. PMID 7337818.
  2. ^ "Euglenozoa". Retrieved 21 May 2013.
  3. ^ a b David J. Patterson (1999). "The Diversity of Eukaryotes". American Naturalist. 154 (S4): S96–S124. doi:10.1086/303287. PMID 10527921.
  4. ^ Do Red and Green Make Brown?: Perspectives on Plastid Acquisitions within Chromalveolates - NCBI
  5. ^ Alastair G. B. Simpson (1997). "The Identity and Composition of Euglenozoa". Archiv für Protistenkunde. 148 (3): 318–328. doi:10.1016/s0003-9365(97)80012-7.
  6. ^ Baldauf, S. L.; Roger, A. J.; Wenk-Siefert, I.; Doolittle, W. Ford (2000). "A Kingdom-Level Phylogeny of Eukaryotes Based on Combined Protein Data". Science. 290 (5493): 972–977. Bibcode:2000Sci...290..972B. doi:10.1126/science.290.5493.972. PMID 11062127.
  7. ^ Alastair G. Simpson (2003). "Cytoskeletal organization, phylogenetic affinities and systematics in the contentious taxon Excavata (Eukaryota)". International Journal of Systematic and Evolutionary Microbiology. 53 (Pt 6): 1759–1777. doi:10.1099/ijs.0.02578-0. PMID 14657103.
  8. ^ Cavalier-Smith T (December 2009). "Kingdoms Protozoa and Chromista and the eozoan root of the eukaryotic tree". Biol Lett. 6 (3): 342–5. doi:10.1098/rsbl.2009.0948. PMC 2880060. PMID 20031978.[permanent dead link]
  9. ^ a b Thomas Cavalier-Smith (2016). "Higher Classification and Phylogeny of Euglenozoa". European Journal of Protistology. 56: 250–276. doi:10.1016/j.ejop.2016.09.003. PMID 27889663.
  10. ^ Thomas Cavalier-Smith (2017). "Euglenoid pellicle morphogenesis and evolution in light of comparative ultrastructure and trypanosomatid biology: Semi-conservative microtubule/strip duplication, strip shaping and transformation". European Journal of Protistology. 61 (A): 137–179. doi:10.1016/j.ejop.2017.09.002. PMID 29073503.

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