Euglenozoa

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Euglenozoa
Euglena
Scientific classification
Domain: Eukarya
Kingdom: Excavata
Phylum: Euglenozoa
Class: Euglenoidea
Kinetoplastea

The Euglenozoa are a large phylum of flagellate protists. They are part of the wastebasket taxon known as the Protozoa, which contained many obviously different protists.

Euglenozoa include a variety of common free-living species, and some important parasites, of which a few infect humans. There are two main subgroups, the euglenids and kinetoplastids.[1] Euglenozoa are unicellular, mostly around 15–40 µm in size, although some euglenids get up to 500 µm long.

Most euglenozoa have two flagella, parallel to one another in an pocket-like structure. In some there is a cytostome or mouth, used to ingest bacteria or other small organisms. This is supported by a microtubule from the flagellar bases; two other tubules support the dorsal and ventral surfaces of the cell.[2]

Some other euglenozoa feed through the absorption, and many euglenids possess chloroplasts and so obtain energy through photosynthesis. These chloroplasts are surrounded by three membranes and contain chlorophylls A and C, along with other pigments,[1] so are probably evolved from those of 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.[2]

The group is characterized by the ultrastructure of the flagella. In addition to the normal supporting microtubules, each contains a rod (called paraxonemal), which has a tubular structure in one flagellum and a latticed structure in the other.[3]

Classification[change | change source]

The euglenozoa are generally accepted as monophyletic. They are related to Percolozoa; the two share mitochondria with disk-shaped compartments, which only occurs in a few other groups.[4] Both probably belong to a larger group of eukaryotes called the Excavata.[5] This grouping, though, has been challenged.[6]

References[change | change source]

  1. 1.0 1.1 Cavalier-Smith T. 1981. Eukaryote kingdoms: seven or nine?. BioSystems 14 (3–4): 461–481. doi:10.1016/0303-2647(81)90050-2 . PMID 7337818 .
  2. 2.0 2.1 Patterson, David J. 1999. The diversity of eukaryotes. American Naturalist 154 (S4): S96–S124. doi:10.1086/303287 . PMID 10527921 .
  3. Simpson A.G.B. 1997. The identity and composition of Euglenozoa. Archiv für Protistenkunde 148: 318–328.
  4. 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. [1]
  5. Simpson, Alastair G. 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 .
  6. Cavalier-Smith T 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 . http://rsbl.royalsocietypublishing.org/cgi/pmidlookup?view=long&pmid=20031978.