Xenoturbella japonica

Xenoturbella japonica is a marine benthic worm-like species that belongs to the genus Xenoturbella. It has been discovered in western Pacific Ocean by a group of Japanese scientists from the University of Tsukuba. The species was described in 2017 in a study published in the journal BMC Evolutionary Biology,[1] and amended in 2018.[2]

Xenoturbella japonica
X. japonica holotype female. The white arrowhead indicates the ring furrow.
Scientific classification
Kingdom: Animalia
Phylum: Xenacoelomorpha
Family: Xenoturbellidae
Genus: Xenoturbella
Species:
X. japonica
Binomial name
Xenoturbella japonica
Nakano, Miyazawa, Maeno, Shiroishi, Kakui, Koyanagi, Kanda, Satoh, Omori & Kohtsuka, 2018
Longitudinal section of a congeneric species, Xenoturbella bocki

Xenotrubella japonica is known for lacking respiratory, circulatory and an excretory system.[3][4][1]

Description

The etymology of the species name corresponds to the locality where the specimens were sampled.

Xenoturbella japonica is 5.3 cm (2.1 in) in length, with a pale orange colouration. The body wall displays ring and side furrows. The mouth is orientated ventrally, just anterior to the ring furrow. The live specimen exhibits a conspicuous ventral epidermal glandular network.[1] Tissues contain exogenous DNA corresponding to bivalve mollusks, the vesicomyid Acila castrensis and Nucula nucleus.[1]

Phylogeny

Comparison of mitochondrial DNA and protein sequences showed that the species Xenoturbella japonica is the sister group to X. bocki and X. hollandorum into a clade of 'shallow-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.[5][1]

References
  1. Nakano, Hiroaki; Miyazawa, Hideyuki; Maeno, Akiteru; Shiroishi, Toshihiko; Kakui, Keiichi; Koyanagi, Ryo; Kanda, Miyuki; Satoh, Noriyuki; Omori, Akihito; Kohtsuka, Hisanori (2017). "A new species of Xenoturbella from the western Pacific Ocean and the evolution of Xenoturbella". BMC Evolutionary Biology. 17 (1). doi:10.1186/s12862-017-1080-2. PMC 5733810. PMID 29249199.
  2. Nakano, Hiroaki; Miyazawa, Hideyuki; Maeno, Akiteru; Shiroishi, Toshihiko; Kakui, Keiichi; Koyanagi, Ryo; Kanda, Miyuki; Satoh, Noriyuki; Omori, Akihito; Kohtsuka, Hisanori (2018-06-07). "Correction to: A new species of Xenoturbella from the western Pacific Ocean and the evolution of Xenoturbella". BMC Evolutionary Biology. 18 (1): 83. doi:10.1186/s12862-018-1190-5. ISSN 1471-2148. PMC 5991446. PMID 29879905.
  3. Georgiou, Aristo (19 December 2017). "Mysterious new deep-sea species with no anus sheds light on early evolution". International Business Times. Retrieved 28 December 2017.
  4. "Mysterious new seafloor species sheds light on early animal evolution". Phys.org. 19 December 2017. Retrieved 28 December 2017.
  5. 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.


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