Misplaced Pages

Spirocuta
Cell exhibiting 'euglenoid motion' or metaboly, characteristic of this clade
Scientific classification
Domain:	Eukaryota
Phylum:	Euglenozoa
Class:	Euglenida
Clade:	Spirocuta Cavalier-Smith, 2016
Orders
Anisonemia Anisonemida Natomonadida Peranemida Euglenophyceae Rapazida Eutreptiales Euglenales
Synonyms
Helicales Paerschke et al., 2017

Spirocuta (from Latin spira 'coil, spire' and cutis 'skin') is a clade of euglenids, single-celled eukaryotes or protists belonging to the phylum Euglenozoa. They are distinguished from other euglenids by active deformation of their cell shape, a process called euglenid motion or metaboly. This is made possible by a high number of spirally arranged protein strips that run below their cell membrane and confer the cell with flexibility. These strips compose the helicoidal pellicle, a trait referenced by the alternative name Helicales.

Description

Spirocuta is a group of flagellates, unicellular eukaryotes or protists with one or two flagella for locomotion in the anterior region of the cell. The move through a gliding motion in contact with the substrate to propel the cell forward. Like other members of the Euglenida, their cells are lined by a pellicle composed of proteinaceous strips that interlock with each other, and are spirally arranged underneath the cell membrane. In particular, members of Spirocuta share a synapomorphy, or unique trait: their high number of strips (between 16 and 56) confers the cells with an immense flexibility, allowing them to actively stretch and deform. This process is known as metaboly or euglenid motion.

Classification

Spirocuta was first proposed by American protozoologist Thomas Cavalier-Smith in 2016, as a superclass uniting all those euglenids with more than 15 spirally arranged pellicle strips. It was named in reference of this characteristic, from Latin spira 'coil, spire' and cutis 'skin'. It contained two classes: Euglenophyceae, a monophyletic group of phototrophs, and Peranemea, a paraphyletic group of heterotrophs. Later, Peranemea was separated into two distinct clades: Peranemida, a group of phagotrophs whose monophyly is yet to be proven, and Anisonemia, which contains various phagotrophs and a clade of osmotrophs known as Aphagea. In 2017, Stefan Paerschke and colleagues independently noticed the same clade through phylogenetic analyses, and named it Helicales in reference to the helical pellicle composed of spirally arranged strips. The following cladogram depicts the evolutionary relationships of Spirocuta according to phylogenetic studies published in the early 2020s:

References

1. ^ Thomas Cavalier-Smith (15 September 2016). "Higher classification and phylogeny of Euglenozoa". European Journal of Protistology. 56: 250–276. doi:10.1016/J.EJOP.2016.09.003. ISSN 0932-4739. PMID 27889663. Wikidata Q39151632.
2. ^ Gordon Lax; Anna Cho; Patrick J. Keeling (30 March 2023). "Phylogenomics of novel ploeotid taxa contribute to the backbone of the euglenid tree". Journal of Eukaryotic Microbiology. 70 (4). doi:10.1111/JEU.12973. ISSN 1066-5234. Wikidata Q123348233.
3. ^ Alexei Y. Kostygov; Anna Karnkowska; Jan Votýpka; Daria Tashyreva; Kacper Maciszewski; Vyacheslav Yurchenko; Julius Lukeš (10 March 2021). "Euglenozoa: taxonomy, diversity and ecology, symbioses and viruses". Open Biology. 11: 200407. doi:10.1098/RSOB.200407. ISSN 2046-2441. PMC 8061765. PMID 33715388. Wikidata Q125548575.
4. ^ Stefan Paerschke; Almut H. Vollmer; Angelika Preisfeld (8 May 2017). "Ultrastructural and immunocytochemical investigation of paramylon combined with new 18S rDNA-based secondary structure analysis clarifies phylogenetic affiliation of Entosiphon sulcatum (Euglenida: Euglenozoa)". Organisms Diversity and Evolution. 17 (1): 509–520. doi:10.1007/S13127-017-0330-X. ISSN 1439-6092. Wikidata Q125677096.
5. Gordon Lax; Alastair G. B. Simpson (16 August 2020). "The Molecular Diversity of Phagotrophic Euglenids Examined Using Single-cell Methods". Protist. 171 (5): 125757. doi:10.1016/J.PROTIS.2020.125757. ISSN 1434-4610. PMID 33126020. Wikidata Q101127864.
6. Brian S Leander; Heather J Esson; Susana A Breglia (1 October 2007). "Macroevolution of complex cytoskeletal systems in euglenids". BioEssays. 29 (10): 987–1000. doi:10.1002/BIES.20645. ISSN 0265-9247. PMID 17876783. Wikidata Q33299331.
7. ^ G. Lax; M. Kolisko; Y. Eglit; et al. (June 2021). "Multigene phylogenetics of euglenids based on single-cell transcriptomics of diverse phagotrophs". Molecular Phylogenetics and Evolution. 159: 107088. doi:10.1016/J.YMPEV.2021.107088. ISSN 1055-7903. Wikidata Q110667805.

• Euglenozoa taxa
• Taxa described in 2016
• Taxa named by Thomas Cavalier-Smith