Xenoturbella churro

Xenoturbella churro is a marine, benthic, deep-water worm-like species that belongs to the genus Xenoturbella. It was discovered in eastern Pacific Ocean by a group of Californian and Australian scientists.[2][3][4] The species was described in 2016 from a single specimen.[1]

Xenoturbella churro
A congeneric species of X. churro (X. japonica)
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Xenacoelomorpha
Family: Xenoturbellidae
Genus: Xenoturbella
Species:
X. churro
Binomial name
Xenoturbella churro
Rouse, Wilson, Carvajal & Vrijenhoek, 2016[1]
Longitudinal section of a congeneric species, Xenoturbella bocki

X. churro shares morphological similarities with other species of the genus Xenoturbella, and is known for lacking respiratory, circulatory and an excretory system.[5]

Description

The etymology of the species name refers to the resemblance with churro, a fried-dough pastry.[6]

This animal is 10 cm (3.9 in) in length, with a uniform orange/pink colouration. The body wall displays several furrows: on the circumference, on the side, and four deep, longitudinal, dorsal ones. The longitudinal orientation involves a rounded anterior end, while the posterior end sharply reduces in thickness. The mouth is orientated ventrally, halfway between the anterior end and the ring furrow. The live specimen exhibited an epidermal ventral glandular network branching over two-thirds of the ventral surface. Gametes are present dorsally and ventrally in the body wall.[1] Tissues contain exogenous DNA corresponding to a bivalve mollusk, the vesicomyid Calyptogena pacifica.[1]

Phylogeny

Comparison of mitochondrial DNA and protein sequences showed that the species X. churro is the sister group to X. profunda. In turn, these two species share evolutionary affinities with X. monstrosa into a clade of 'deep-water' taxa.

Species-level cladogram of the genus Xenoturbella.
  Xenacoelomorpha  
  Xenoturbella  
  'Shallow' clade  
         

  X. japonica

         

  X. bocki

  X. hollandorum

  'Deep' clade  
         

  X. monstrosa

         

  X. churro

  X. profunda

  Acoelomorpha  

The cladogram has been reconstructed from mitochondrial DNA and protein sequences.[1][7]

References
  1. Rouse, Greg W.; Wilson, Nerida G.; Carvajal, Jose I.; Vrijenhoek, Robert C. (2016-02-04). "New deep-sea species of Xenoturbella and the position of Xenacoelomorpha". Nature. 530 (7588): 94–97. doi:10.1038/nature16545. ISSN 0028-0836. PMID 26842060. S2CID 3870574.
  2. Khan, Amina (2016-02-05). "Newly discovered deep-sea worms, including one named 'churro,' could shed light on animal evolution". Los Angeles Times. Retrieved 2020-03-10.
  3. Morelle, Rebecca (2016-02-03). "Mystery of 'sock of the deep' solved". BBC News. Retrieved 2020-03-10.
  4. "We finally know what to make of these 'purple sock' creatures that litter the sea floor". ZME Science. 2016-02-05. Retrieved 2020-03-11.
  5. Nakano, Hiroaki (2015). "What is Xenoturbella?". Zoological Letters. 1 (22): 22. doi:10.1186/s40851-015-0018-z. PMC 4657256. PMID 26605067.
  6. "Around the Pier: Churro-Like Marine Worm Discovered by Scripps Scientists Is One of the 'Top 10 Species of 2017'". Scripps Institution of Oceanography. 2017-05-30. Retrieved 2020-03-10.
  7. Nakano, Hiroaki; Miyazawa, Hideyuki; Maeno, Akiteru; Shiroishi, Toshihiko; Kakui, Keiichi; Koyanagi, Ryo; Kanda, Miyuki; Satoh, Noriyuki; Omori, Akihito; Kohtsuka, Hisanori (2017-12-18). "A new species of Xenoturbella from the western Pacific Ocean and the evolution of Xenoturbella". BMC Evolutionary Biology. 17 (1): 245. doi:10.1186/s12862-017-1080-2. ISSN 1471-2148. PMC 5733810. PMID 29249199.


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