Euglenozoa are a large group of

flagellate A flagellate is a cell or organism with one or more whip-like appendages called flagella. The word ''flagellate'' also describes a particular construction (or level of organization) characteristic of many prokaryotes and eukaryotes and thei ...

Discoba Excavata is a major supergroup of unicellular organisms belonging to the domain Eukaryota. It was first suggested by Simpson and Patterson in 1999 and introduced by Thomas Cavalier-Smith in 2002 as a formal taxon. It contains a variety of fr ...

. They include a variety of common free-living species, as well as a few important parasites, some of which infect humans. Euglenozoa are represented by three major clades, i.e., Kinetoplastea, Diplonema and Symbiontida. Euglenozoa are unicellular, mostly around in size, although some euglenids get up to long.

Structure

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 A cytostome (from ''cyto-'', cell and ''stome-'', mouth) or cell mouth is a part of a cell specialized for phagocytosis, usually in the form of a microtubule-supported funnel or groove. Food is directed into the cytostome, and sealed into vacuole ...

or mouth, used to ingest

bacteria Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were am ...

or other small organisms. This is supported by one of three sets of

microtubule Microtubules are polymers of tubulin that form part of the cytoskeleton and provide structure and shape to eukaryotic cells. Microtubules can be as long as 50 micrometres, as wide as 23 to 27 nm and have an inner diameter between 1 ...

s that arise from the flagellar bases; the other two support the dorsal and ventral surfaces of the cell. Some other euglenozoa feed through absorption, and many euglenids possess

chloroplast A chloroplast () is a type of membrane-bound organelle known as a plastid that conducts photosynthesis mostly in plant and algal cells. The photosynthetic pigment chlorophyll captures the energy from sunlight, converts it, and stores it i ...

s, the only eukaryotes outside

Diaphoretickes Diaphoretickes () is a major group of eukaryotic organisms, with over 400,000 species. The majority of the earth's biomass that carries out photosynthesis belongs to Diaphoretickes. Diaphoretickes includes: * Archaeplastida (comprising red alg ...

to do so without performing kleptoplasty, and so obtain energy through

photosynthesis Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that, through cellular respiration, can later be released to fuel the organism's activities. Some of this chemical energy is stored in ...

. These chloroplasts are surrounded by three membranes and contain

chlorophyll Chlorophyll (also chlorophyl) is any of several related green pigments found in cyanobacteria and in the chloroplasts of algae and plants. Its name is derived from the Greek words , ("pale green") and , ("leaf"). Chlorophyll allow plants to ...

s ''A'' and ''B'', along with other pigments, so are probably derived from a captured

green alga The green algae (singular: green alga) are a group consisting of the Prasinodermophyta and its unnamed sister which contains the Chlorophyta and Charophyta/Streptophyta. The land plants (Embryophytes) have emerged deep in the Charophyte alga as ...

. Reproduction occurs exclusively through cell division. During

mitosis In cell biology, mitosis () is a part of the cell cycle in which replicated chromosomes are separated into two new nuclei. Cell division by mitosis gives rise to genetically identical cells in which the total number of chromosomes is maintai ...

, 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''.

Classification

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. Both probably belong to a larger group of eukaryotes called the Excavata. This grouping, though, has been challenged.

Phylogeny

The phylogeny based on the work of Cavalier-Smith (2016): A consensus phylogeny following the review by Kostygov ''et al.'' (2021):

Taxonomy

Cavalier-Smith (2016/2017)

The following classification of Euglenozoa is as described by Cavalier-Smith in 2016, modified to include the new subphylum Plicomonada according to Cavalier-Smith ''et al'' (2017). Phylum Euglenozoa Cavalier-Smith 1981 emend. Simpson 1997 uglenobionta* Subphylum Glycomonada Cavalier-Smith 2016 ** Class Diplonemea Cavalier-Smith 1993 emend. Simpson 1997 iplosonematea; Diplonemia Cavalier-Smith 1993*** Order Diplonemida Cavalier-Smith 1993 emistasiida**** Family Hemistasiidae Cavalier-Smith 2016 ntomosigmaceae **** Family

Diplonemidae Diplonemidae is a family of biflagellated unicellular protists that may be among the more diverse and common groups of planktonic organisms in the ocean. Although this family is currently made up of three named genera; '' Diplonema'', '' Rhynchopu ...

Cavalier-Smith 1993 hynchopodaceae Skuja 1948 ex Cavalier-Smith 1993** Class Kinetoplastea Honigberg 1963 emend. Margulis 1974 inetoplastida Honigberg 1963; Kinetoplasta Honigberg 1963 stat. nov. *** Subclass Prokinetoplastina Vickerman 2004 **** Order Prokinetoplastida Vickerman 2004 ***** Family Ichthyobodonidae Isaksen et al., 2007 *** Subclass Metakinetoplastina Vickerman 2004 **** Order Bodonida* Hollande 1952 em. Vickerman 1976, Kryov et al 1980 ***** Suborder Neobodonida Vickerman 2004 ****** Family Rhynchomonadidae Cavalier-Smith 2016 ****** Family Neobodonidae Cavalier-Smith 2016 ***** Suborder Parabodonida Vickerman 2004 ****** Family Parabodonidae Cavalier-Smith 2016