Symbiontida
| Symbiontida | |
|---|---|
| Calkinsia aurea | |
| Scientific classification Edit this classification | |
| Domain: | Eukaryota |
| Clade: | Discoba |
| Phylum: | Euglenozoa |
| Class: | Symbiontida Yubuki et al., 2009[1] |
| Genera | |
| Synonyms | |
| |
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Symbiontida is a basal class of flagellate Euglenozoa.[2] [3] As euglenozoans may be basal eukaryotes, the Symbiontida may be key to studying the evolution of eukaryotes, including the incorporation of eukaryotic traits such as the incorporation of alphaproteobacterial mitochondrial endosymbionts.
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 infect humans. Euglenozoa are represented by four major classes, i.e., Kinetoplastea, Diplonemea, Euglenida, and Symbiontida. Euglenozoa are unicellular, mostly around 15–40 μm (0.00059–0.00157 in) in size, although some euglenids get up to 500 μm (0.020 in) long.[4]
Characteristics
[edit ]Euglenozoa are 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 are included: the diplonemids and Postgaardi .[5]
Symbiontida is a third deep-branching euglenozoan clade that may be a sister to Euglenoida but does not branch within them or Glycomonada on the evolutionary most realistic sequence trees presented in the next three sections, contrary to some poorly resolved earlier trees. They were placed in the new subphylum Postgaardia as class Postgaardea because they are radically different ultrastructurally from both euglenoids and glycomonads.[2]
Symbiontida are biciliate free-living anaerobes covered in epibiotic bacteria in longitudinal rows are the diagnosis. A highly contractile pellicle with multiple evenly spaced microtubules and no morphogenetic pairs that are specifically distinguished. Without cytostomal or reservoir encircling fibers, cemented jaw supports, or hard longitudinal straight cemented rods, the cytopharynx is simplified. Symbiontida is the lone included class in etymology.[2]
Reconstructions of FA ultrastructure in Postgaardi and Calkinsia confirmed that they were fundamentally similar and deserved to be classified together as a distinct order Postgaardida and class Postgaardea, as both genera share six finger-like projections.[2]
Taxonomy
[edit ]According to Cavalier-Smith (2017):[6]
- Infraphylum Postgaardia Cavalier-Smith 2016 stat. nov. Cavalier-Smith 2017
- Class Postgaardea Cavalier-Smith 1998 s.s. [Symbiontida Yubuki et al., 2009]
- Order Bihospitida Cavalier-Smith 2016
- Family Bihospitidae Cavalier-Smith 2016
- Order Postgaardida Cavalier-Smith 2003
- Family Calkinsiidae Cavalier-Smith 2016
- Family Postgaardidae Cavalier-Smith 2016
- Order Bihospitida Cavalier-Smith 2016
- Class Postgaardea Cavalier-Smith 1998 s.s. [Symbiontida Yubuki et al., 2009]
According to Kostygov et al. (2023):[3]
- Class Symbiontida Yubuki, Edgcomb, Bernhard & Leander 2009
- Bihospites Breglia, Yubuki, Hoppenrath & Leander 2010
- Calkinsia Lackey 1960
- Postgaardi Fenschel, Bernard, Esteban, Findlay, Hansen & Iversen 1995
References
[edit ]- ^ Yubuki, Naoji; Edgcomb, Virginia P.; Bernhard, Joan M.; Leander, Brian S. (27 January 2009). "Ultrastructure and molecular phylogeny of Calkinsia aureus: cellular identity of a novel clade of deep-sea euglenozoans with epibiotic bacteria". BMC Microbiology. 9 (1): 16. doi:10.1186/1471-2180年9月16日 . ISSN 1471-2180. PMC 2656514 . PMID 19173734.
- ^ a b c d Cavalier-Smith, Thomas (2016). "Higher classification and phylogeny of Euglenozoa". European Journal of Protistology. 56: 250–276. doi:10.1016/j.ejop.201609003 . PMID 27889663.
- ^ a b Kostygov, Alexei Y.; Karnkowska, Anna; Tashyreva, Daria; Maciszewski, Kacper & Lukeš, Julius (2021). "Euglenozoa: taxonomy, diversity and ecology, symbioses and viruses". Open Biology. 11 (3). doi:10.1098/rsob.200407. PMC 8061765 . PMID 33715388.
- ^ "Euglenozoa". Encyclopedia of Life. National Museum of Natural History - Smithsonian Institution. Retrieved 16 January 2020.
- ^ Simpson AG (1997). "The Identity and Composition of Euglenozoa". Archiv für Protistenkunde. 148 (3): 318–328. doi:10.1016/s0003-9365(97)80012-7.
- ^ Cavalier-Smith, Thomas (2017). "Euglenoid pellicle morphogenesis and evolution in light of comparative ultrastructure and trypanosomatid biology: Semi-conservative microtubule/Strip duplication, strip shaping and transformation". European Journal of Protistology. 61 (Pt A): 137–179. doi:10.1016/j.ejop.201709002 . PMID 29073503.
