Euglenozoa are a large group of flagellate

Discoba Excavata is a major supergroup of unicellular organisms belonging to the Domain (biology), 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 ...

. 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 Kinetoplastida (or Kinetoplastea, as a class) is a group of flagellated protists belonging to the phylum Euglenozoa, and characterised by the presence of an organelle with a large massed DNA called kinetoplast (hence the name). The organisms are ...

, 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 vacuol ...

or mouth, used to ingest

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

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. Some other euglenozoa feed through absorption, and many euglenids possess chloroplasts, 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 Kleptoplasty or kleptoplastidy is a symbiotic phenomenon whereby plastids, notably chloroplasts from algae, are sequestered by host organisms. The word is derived from ''Kleptes'' (κλέπτης) which is Greek for thief. The alga is eaten norma ...

, 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 i ...

. 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 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, 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 An axoneme, also called an axial filament is the microtubule-based cytoskeletal structure that forms the core of a cilium or flagellum. Cilia and flagella are found on many cells, organisms, and microorganisms, to provide motility. The axo ...

, 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

diplonemid 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'', ''Rhynchopus ...

s and ''

Postgaardi ''Postgaardi mariagerensis'' is a species of single-celled eukaryote in the Euglenozoa Euglenozoa are a large group of flagellate Discoba. They include a variety of common free-living species, as well as a few important parasites, some of which ...

''.

Classification

The euglenozoa are generally accepted as monophyletic. They are related to

Percolozoa The Percolozoa are a group of colourless, non-photosynthetic Excavata, including many that can transform between amoeboid, flagellate, and cyst stages. Characteristics Most Percolozoa are found as bacterivores in soil, fresh water and occasio ...

; the two share mitochondria with disk-shaped

cristae A crista (; plural cristae) is a fold in the inner membrane of a mitochondrion. The name is from the Latin for ''crest'' or ''plume'', and it gives the inner membrane its characteristic wrinkled shape, providing a large amount of surface area fo ...

, which only occurs in a few other groups. Both probably belong to a larger group of eukaryotes called the

Excavata 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 free- ...

. 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 Glycomonada are a proposed basal Euglenozoan clade, following Cavalier-Smith. As Euglenozoans may be basal Eukaryote Eukaryotes () are organisms whose cells have a nucleus. All animals, plants, fungi, and many unicellular organisms, are Eu ...

Cavalier-Smith 2016 ** Class

Diplonemea 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'', ''Rhynchopus ...

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 Cavalier-Smith 1993 hynchopodaceae Skuja 1948 ex Cavalier-Smith 1993** Class

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