A new species of Xenoturbella from the western Pacific Ocean and the evolution of Xenoturbella

Xenoturbella is a group of marine benthic animals lacking an anus and a centralized nervous system. Molecular phylogenetic analyses group the animal together with the Acoelomorpha, forming the Xenacoelomorpha. This group has been suggested to be either a sister group to the Nephrozoa or a deuterosto...

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Bibliographic Details
Published in:BMC evolutionary biology 2017-12, Vol.17 (1), p.245-245, Article 245
Main Authors: Nakano, Hiroaki, Miyazawa, Hideyuki, Maeno, Akiteru, Shiroishi, Toshihiko, Kakui, Keiichi, Koyanagi, Ryo, Kanda, Miyuki, Satoh, Noriyuki, Omori, Akihito, Kohtsuka, Hisanori
Format: Article
Language:English
Subjects:
Acoelomorpha
Acoels
Animals
Biological Evolution
Biological research
Biology, Experimental
Deuterostomia
Evolutionary biology
Frontal organ
Identification and classification
Invertebrates - anatomy & histology
Nemertodermatids
Pacific Ocean
Phylogeny
Species Specificity
X-Ray Microtomography
Xenacoelomorpha
Xenoturbella
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Summary:Xenoturbella is a group of marine benthic animals lacking an anus and a centralized nervous system. Molecular phylogenetic analyses group the animal together with the Acoelomorpha, forming the Xenacoelomorpha. This group has been suggested to be either a sister group to the Nephrozoa or a deuterostome, and therefore it may provide important insights into origins of bilaterian traits such as an anus, the nephron, feeding larvae and centralized nervous systems. However, only five Xenoturbella species have been reported and the evolutionary history of xenoturbellids and Xenacoelomorpha remains obscure. Here we describe a new Xenoturbella species from the western Pacific Ocean, and report a new xenoturbellid structure - the frontal pore. Non-destructive microCT was used to investigate the internal morphology of this soft-bodied animal. This revealed the presence of a frontal pore that is continuous with the ventral glandular network and which exhibits similarities with the frontal organ in acoelomorphs. Our results suggest that large size, oval mouth, frontal pore and ventral glandular network may be ancestral features for Xenoturbella. Further studies will clarify the evolutionary relationship of the frontal pore and ventral glandular network of xenoturbellids and the acoelomorph frontal organ. One of the habitats of the newly identified species is easily accessible from a marine station and so this species promises to be valuable for research on bilaterian and deuterostome evolution.
ISSN:1471-2148
1471-2148
DOI:10.1186/s12862-017-1080-2