Euglenozoa

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

Euglenozoa Temporal range: Stenian (over 1000 MYA) - present [1] Had'n Archean Proterozoic Pha.
Two Euglena
Scientific classification
Domain:	Eukaryota
Superphylum:	Discicristata
Phylum:	Euglenozoa Cavalier-Smith, 1981[2]
Classes
Diplonemea Euglenida Kinetoplastea Symbiontida (Postgaardia)

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".^[3] 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.^[4]

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,^[3] 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.^[4]

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.^[5]

Classification

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.^[6] Both probably belong to a larger group of eukaryotes called the Excavata.^[7] This grouping has been challenged.^[8]