Euglenozoa

From Wikipedia, the free encyclopedia
  (Redirected from Euglenophyte)
Jump to: navigation, search
Euglenozoa
Two Euglena.jpg
Two Euglena
Scientific classification
Domain: Eukarya
Kingdom: Excavata
Phylum: Euglenozoa
Cavalier-Smith, 1981[1]
Classes and unplaced genera

Euglenoidea
Kinetoplastea
Diplonemea
Postgaardi
Calkinsia

The 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.[2]

Structure[edit]

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 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.[4]

Classification[edit]

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.[5] Both probably belong to a larger group of eukaryotes called the excavates.[6] This grouping, though, has been challenged.[7]

References[edit]

  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. ^ Alastair G.B. Simpson (1997). "The Identity and Composition of Euglenozoa". Archiv für Protistenkunde 148: 318–328. doi:10.1016/s0003-9365(97)80012-7. 
  5. ^ 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. doi:10.1126/science.290.5493.972. PMID 11062127.  edit
  6. ^ 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. 
  7. ^ 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. 

External links[edit]