History

Honigberg created the taxonomic names Kinetoplastida and Kinetoplastea in 1963.^[1] Since then there is no consensus on the use of either of the two as a definite taxon. Kinetoplastea is more widely used as the class,^{[6][7][8][9][10]} while Kinetoplastida is mostly used to designate the order,^{[4][11][12][13]} but is also used as a class.^[3][14] Lynn Margulis, who initially accepted Kinetoplastida as an order in 1974, later placed it as a class.^[15] Use of Kinetoplastida as an order also creates confusion as there is already an older name Trypanosomatida Kent, 1880, under which the kinetoplastids are most often placed.^[16]

Classification

Kinetoplastida is divided into two subclasses - Metakinetoplastina and Prokinetoplastina.^[17][18]

• Family ?Bordnamonadidae Cavalier-Smith 2013
• Family ?Trypanophididae Poche 1911
• Subclass Prokinetoplastina Vickerman 2004
  • Order Prokinetoplastida Vickerman 2004
    • Family Ichthyobodonidae Isaksen et al. 2007
• Subclass Metakinetoplastina Vickerman 2004
  • Order Neobodonida Vickerman 2004
    • Family Rhynchomonadidae Cavalier-Smith 2016
    • Family Neobodonidae Cavalier-Smith 2016
  • Order Parabodonida Vickerman 2004
    • Family Parabodonidae Cavalier-Smith 2016 [Cryptobiaceae Poche 1911; Cryptobiidae Vickerman 1976; Trypanoplasmatidae Hartmann & Chagas 1910]
  • Order Bodonida Hollande 1952 emend. Vickerman 1976
    • Family Bodonidae Bütschli 1883
  • Order Trypanosomatida Kent 1880 stat. n. Hollande 1952 emend. Vickerman 2004
    • Family Trypanosomatidae Doflein 1901 [Trypanomorphidae Woodcock 1906]

Mitochondrion and kinetoplast DNA

The kinetoplast, after which the class is named, is a dense DNA-containing granule within the cell's single mitochondrion, containing many copies of the mitochondrial genome. The structure is made up of a network of concatenated circular DNA molecules and their related structural proteins along with DNA and RNA polymerases. The kinetoplast is found at the base of a cell's flagella and is associated to the flagellum basal body by a cytoskeletal structure.^{[citation needed]}

Cytoskeleton

The cytoskeleton of kinetoplastids is primarily made up of microtubules. These make a highly regular array, the sub-pellicular array, which runs parallel just under the cell surface along the long axis of the cell. Other microtubules with more specialised roles, such as the rootlet microtubules, are also present. Kinetoplastids are capable of forming actin microfilaments but their role in the cytoskeleton is not clear. Other cytoskeletal structures include the specialised attachment between the flagellum and the kinetoplast.^{[citation needed]}

Flagella

All kinetoplastids possess at least one flagellum; species in the order trypanosomatida have one and bodonida have two. In kinetoplastids with two flagella most forms have a leading and trailing flagellum, the latter of which may be attached to the side of the cell. The flagella are used for locomotion and attachment to surfaces. The bases of the flagella are found in a specialised pocket structure which is also the location of the cytostome.^{[citation needed]}