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 Euglenoidea "euglenids" and Kinetoplastea "kinetoplastids". 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 a pocket-like structure. In some there is a cytostome or mouth, used to eat 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.
Some other Euglenozoa feed through absorption, and many euglenids have chloroplasts and so get energy by photosynthesis. These chloroplasts are surrounded by three membranes and contain chlorophylls A and C, and other pigments, so are probably evolved from those of a captured green alga. Reproduction occurs only by cell division. During mitosis, the nuclear membrane remains intact, and the spindle microtubules form inside it.
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.
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. Both probably belong to a larger group of eukaryotes called the Excavata. This grouping has been challenged.
References[change | change source]
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- Simpson A.G.B. 1997. "The identity and composition of Euglenozoa". Archiv für Protistenkunde. 148: 318–328.
- 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. 
- 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.
- Cavalier-Smith T 2009. Kingdoms Protozoa and Chromista and the eozoan root of the eukaryotic tree. "Archived copy". Biol Lett. 6 (3): 342–5. doi:10.1098/rsbl.2009.0948. PMC 2880060. PMID 20031978. Archived from the original on 2020-05-20. Retrieved 2013-01-22.CS1 maint: archived copy as title (link)