Xenoturbella japonica
{{short description|Species of bilaterians with a simple body plan}}
{{Speciesbox
| image = Xenoturbella japonica.jpg
| image_caption = X. japonica holotype female. The white arrowhead indicates the ring furrow.
| taxon = Xenoturbella japonica
| authority = Nakano, Miyazawa, Maeno, Shiroishi, Kakui, Koyanagi, Kanda, Satoh, Omori & Kohtsuka, 2018
}}
File:Xenoturbella bockii longitudinal section English.svg]]
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,{{cite journal |last1=Nakano |first1=Hiroaki |last2=Miyazawa |first2=Hideyuki |last3=Maeno |first3=Akiteru |last4=Shiroishi |first4=Toshihiko |last5=Kakui |first5=Keiichi |last6=Koyanagi |first6=Ryo |last7=Kanda |first7=Miyuki |last8=Satoh |first8=Noriyuki |last9=Omori |first9=Akihito |last10=Kohtsuka |first10=Hisanori |title=A new species of Xenoturbella from the western Pacific Ocean and the evolution of Xenoturbella |journal=BMC Evolutionary Biology |date=2017 |volume=17 |issue=1 |page=245 |doi=10.1186/s12862-017-1080-2 |pmc=5733810 |pmid=29249199 |doi-access=free }} and amended in 2018.{{Cite journal |last1=Nakano |first1=Hiroaki |last2=Miyazawa |first2=Hideyuki |last3=Maeno |first3=Akiteru |last4=Shiroishi |first4=Toshihiko |last5=Kakui |first5=Keiichi |last6=Koyanagi |first6=Ryo |last7=Kanda |first7=Miyuki |last8=Satoh |first8=Noriyuki |last9=Omori |first9=Akihito |last10=Kohtsuka |first10=Hisanori |date=2018-06-07 |title=Correction to: A new species of Xenoturbella from the western Pacific Ocean and the evolution of Xenoturbella |url= |journal=BMC Evolutionary Biology |volume=18 |issue=1 |pages=83 |doi=10.1186/s12862-018-1190-5 |issn=1471-2148 |pmc=5991446 |pmid=29879905 |doi-access=free }}
Xenoturbella japonica is known for lacking respiratory, circulatory and excretory systems.{{cite news |last=Georgiou |first=Aristo |title=Mysterious new deep-sea species with no anus sheds light on early evolution |url=http://www.ibtimes.co.uk/mysterious-new-deep-sea-species-no-anus-sheds-light-early-evolution-1652147 |work=International Business Times |access-date=28 December 2017 |date=19 December 2017}}{{cite news |title=Mysterious new seafloor species sheds light on early animal evolution |url=https://phys.org/news/2017-12-mysterious-seafloor-species-early-animal.html |work=Phys.org |access-date=28 December 2017 |date=19 December 2017}}
Description
The etymology of the species name corresponds to the locality where the specimens were sampled.
Xenoturbella japonica is {{cvt|5.3|cm}} 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. Tissues contain exogenous DNA corresponding to bivalve mollusks, the vesicomyid Acila castrensis and Nucula nucleus.
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.
{{cladogram
|title=Species-level cladogram of the genus Xenoturbella.
|caption=The cladogram has been reconstructed from mitochondrial DNA and protein sequences.{{Cite journal |last1=Rouse |first1=Greg W. |last2=Wilson |first2=Nerida G. |last3=Carvajal |first3=Jose I. |last4=Vrijenhoek |first4=Robert C. |date=2016-02-04 |title=New deep-sea species of Xenoturbella and the position of Xenacoelomorpha |url=http://www.nature.com/articles/nature16545 |journal=Nature |language=en |volume=530 |issue=7588 |pages=94–97 |doi=10.1038/nature16545 |pmid=26842060 |bibcode=2016Natur.530...94R |s2cid=3870574 |issn=0028-0836|url-access=subscription }}
|align=center
|clades={{Cladogram of Xenoturbella species}}
}}
Other facts
Taxonomic Classification and Unique Morphology
Xenoturbella japonica belongs to the genus Xenoturbella, which has its traits as simple organisms with simple body structures and lack complex organs such as brain, lungs, gut or excretory organs. There has been a recent debate about in location in the phylogenetic tree. Recent research suggests it belongs to the clade Xenacoelomorpha having close evolutionary relationships with early bilaterians.{{Cite web |last=Starr |first=Michelle |date=20 December 2017 |title=These Deep Sea Worms Without Butts Likely Haven't Evolved For Millions of Years |url=https://www.sciencealert.com/xenoturbella-japonica-new-species-primitive-seafloor-worm-evolution |access-date=2 November 2024 |website=Science Alert}}
Evolutionary Significance in Understanding Bilaterian Origins
Xenoturbella japonica stands out as a better path to understanding the evolution of the evolution of bilaterians, a group that includes most multicellular animals with bilateral symmetry.{{Cite news |last=WoRMS |date=2024 |title=Xenoturbella japonica Nakano, Miyazawa, Maeno, Shiroishi, Kakui, Koyanagi, Kanda, Satoh, Omori & Kohtsuka, 2018 |url=https://www.marinespecies.org/aphia.php?p=taxdetails&id=1057843 |access-date=2 November 2024 |work=WORMS}}
Genetic Analysis and Ancestral Traits
Genetic analysis of Xenoturbella japonica reveal unique genetic relationship with the other Xenacoelomorpha species, indicating that it an early-diverging bilaterian. This is important for scientists and interested parties on clues about the earliest stages of animal evolution.
References
{{Reflist}}
External links
- {{Commons category-inline|Xenoturbella japonica}}
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