Euglenozoa

Taxobox


image_width = 240px
image_caption = "Euglenozoa"
domain = Eukaryota
regnum = Excavata
phylum = Euglenozoa
phylum_authority = Cavalier-Smith, 1981cite journal | author = T. Cavalier-Smith
title = Eukaryote Kingdoms: Seven or Nine?
journal = BioSystems
year = 1981 | volume = 14 | pages = 461–481
doi = 10.1016/0303-2647(81)90050-2]
subdivision_ranks = Typical Classes
subdivision = Euglenoidea
Kinetoplastea
Diplonemea
PostgaardeaThe Euglenozoa are a large group of flagellate protozoa. 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.

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.cite journal | author = David J. Patterson
title = The Diversity of Eukaryotes
journal = American Naturalist
year = 1999 | volume = 145 | pages = S96–S124]

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 "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.

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".cite journal | author = Alastair G.B. Simpson
title = The Identity and Composition of Euglenozoa
journal = Archiv für Protistenkunde
year = 1997 | volume = 148 | pages = 318–328]

The euglenozoa are generally accepted as monophyletic. They are related to Percolozoa; the two share mitochondria with disc-shaped cristae, which only occurs in a few other groups.cite journal | author = Baldauf "et al."
title = A Kingdom-Level Phylogeny of Eukaryotes Based On Combined Protein Data
journal = Science
year = 2000 | volume = 290 | pages = 972–977
doi = 10.1126/science.290.5493.972
pmid = 11062127] Both probably belong to a larger group of eukaryotes called the excavates.cite journal | author = Alastair G. Simpson
title = Cytoskeletal organization, phylogenetic affinities and systematics in the contentious taxon Excavata (Eukaryota)
journal = International Journal of Systematic and Evolutionary Microbiology
year = 2003 | volume = 53 | pages = 1759–1777
doi = 10.1099/ijs.0.02578-0
pmid = 14657103]

References

External Links

* [http://tolweb.org/Euglenozoa/2405 Tree of Life: Euglenozoa]