Overview
The Euglenozoa are a large group of 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.2]
Some other euglenozoa feed through the absorption, and many euglenids possess chloroplasts and so obtain energy through photosynthesis. These chloroplastsare surrounded by three membranes and contain chlorophylls a and b, along with other pigments[1], 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.[2]
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.[3]
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.[4] Both probably belong to a larger group of eukaryotes called the excavates.[5]
Taxonomy
The Phylum Euglenozoa is further organized into finer groupings including:
- Subphylum (2): Plicostoma · Saccostoma
- Class (4): Diplonemea · Euglenida · Euglenophyceae · Kinetoplastea
- Species: ZipcodeZoo has pages for 1,885 species and subspecies in the Phylum Euglenozoa.
Classes
Diplonemea
Euglenida
The euglenids (or euglenoids) are one of the best-known groups of , commonly found in freshwater especially when it is rich in organic materials, with a few marine and endosymbiotic members. Many euglenids have chloroplasts and produce energy through photosynthesis, but others feed by phagocytosis or strictly by diffusion. They belong to the phylum Euglenophyta, and their cell structure is typical of that group. [more]
Euglenophyceae
The euglenids (or euglenoids) are one of the best-known groups of , commonly found in freshwater especially when it is rich in organic materials, with a few marine and endosymbiotic members. Many euglenids have chloroplasts and produce energy through photosynthesis, but others feed by phagocytosis or strictly by diffusion. They belong to the phylum Euglenophyta, and their cell structure is typical of that group. [more]
Kinetoplastea
More info about the Class Kinetoplastea may be found here.
References
- ^ a b T. Cavalier-Smith (1981). "Eukaryote Kingdoms: Seven or Nine?". BioSystems 14: 461–481. doi:
- ^ a b David J. Patterson (1999). "The Diversity of Eukaryotes". American Naturalist 145: S96–S124.
- ^ Alastair G.B. Simpson (1997). "The Identity and Composition of Euglenozoa". Archiv für Protistenkunde 148: 318–328.
- ^ Baldauf et al. (2000). "A Kingdom-Level Phylogeny of Eukaryotes Based On Combined Protein Data". Science 290: 972–977. doi:
- ^ Alastair G. Simpson (2003). "Cytoskeletal organization, phylogenetic affinities and systematics in the contentious taxon Excavata (Eukaryota)". International Journal of Systematic and Evolutionary Microbiology 53: 1759–1777. doi:
Sources
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