Xenoturbella is a deuterostome that eats molluscs

@article{Bourlat2003XenoturbellaIA,
  title={Xenoturbella is a deuterostome that eats molluscs},
  author={Sarah J. Bourlat and Claus Nielsen and Anne E. Lockyer and D. Timothy J. Littlewood and Maximilian J. Telford},
  journal={Nature},
  year={2003},
  volume={424},
  pages={925-928}
}
Xenoturbella bocki, first described in 1949 (ref. 1), is a delicate, ciliated, marine worm with a simple body plan: it lacks a through gut, organized gonads, excretory structures and coelomic cavities. Its nervous system is a diffuse nerve net with no brain. Xenoturbella's affinities have long been obscure and it was initially linked to turbellarian flatworms. Subsequent authors considered it variously as related to hemichordates and echinoderms owing to similarities of nerve net and epidermal… 

What is Xenoturbella?

  • H. Nakano
  • Biology, Environmental Science
    Zoological Letters
  • 2015
Although recent studies have uncovered many new and crucial facts regarding Xenoturbella, some fundamental biological information, such as phylogeny, complete life cycle, and genome, remain unsolved.

Xenoturbellida: The fourth deuterostome phylum and the diet of worms

The phylogenetic position for Xenoturbella is considered in the light of what is known of its genetics, morphology, and ontogeny and what light this might shine on the common ancestor of the deuterostomes and hence on the origins of the chordates.

Acoelomorph flatworms are deuterostomes related to Xenoturbella

This phylogeny makes sense of the shared characteristics of Xenoturbellida and Acoelomorpha, and implies the loss of various deuterostome characters in the Xenobiology including coelomic cavities, through gut and gill slits.

Feeding ecology of Xenoturbella bocki (phylum Xenoturbellida) revealed by genetic barcoding

Xenoturbella only contains molluscan DNA originating from bivalves living in the same environment, refuting former hypotheses of a bivalve relationship and suggesting that Xenoturblla feeds specifically onbivalve prey from multiple species, possibly in the form of eggs and larvae.

Xenacoelomorpha flatworms are basal Deuterostome

This work sequence Heterochaerus australis’s mitochondrial genome and infer intrinsic relationships of Metazoan with Xenacoelomorpha and finds the optimal tree under the popular maximum likelihood (ML) and Bayesian phylogenetic reconstructions are consensus with each other being strongly supported.

Two Types of Endosymbiotic Bacteria in the Enigmatic Marine Worm Xenoturbella bocki (cid:1) †

Two types of endosymbiotic bacteria were identified in the gastrodermis of the marine invertebrate Xeno- turbella bocki (Xenoturbellida, Bilateria) and should be considered when interpreting the poorly understood ecology and evolution of Xenoturbella.

Review of data for a morphological look on Xenacoelomorpha (Bilateria incertae sedis)

It is suggested that the taxon Xenacoelomorpha represents either a quite plesiomorphic grouping as the earliest bilaterian offshoot or but is a substantially reduced and simplified sidebranch of ambulacralian Deuterostomia.

Acoelomorpha: earliest branching bilaterians or deuterostomes?

It is argued for the benefits of obtaining additional genomic data from acoelomorphs, in particular from taxa with slower evolutionary rates; the development of new tools to analyse the data; and the use of metagenomics or metatranscriptomics data to provide a definitive answer as to the position of the acoels in the animal tree of life.

Xenacoelomorph-Specific Hox Peptides: Insights into the Phylogeny of Acoels, Nemertodermatids, and Xenoturbellids

Results from the decoded genome of the acoel Praesagittifera naikaiensis and reported xenacoelomorph Hox genes revealed that acoels share a peptide NLK(S/T)MSQ(V/I)D, which starts immediately after the homeodomain sequence of the central Hox4/5/6.

Xenoturbella bocki exhibits direct development with similarities to Acoelomorpha

The embryonic stages of Xenoturbella are reported, and it is shown that it is a direct developer without a feeding larval stage, supporting the newly proposed phylum Xenacoelomorpha and suggesting that the last common ancestor of the phylum might have been a direct developers.
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References

SHOWING 1-10 OF 51 REFERENCES

New light on the enigmatic Xenoturbella (phylum uncertain): ontogeny and phylogeny

  • O. Israelsson
  • Biology
    Proceedings of the Royal Society of London. Series B: Biological Sciences
  • 1999
The previously unknown embryology of Xenoturbella is reported here that unequivocally corroborates a bivalve relationship and thus once and for all dismisses the potential new phylum plesiomorphic phylum.

The ciliated epidermis of Xenoturbella bocki (Platyhelminthes, Xenoturbellida) with some phylogenetic considerations

The epidermis of Xenoturbella bocki Westblad was studied by scanning and transmission electron microscopy and showed a characteristic pattern of axonemal filament termination in the distal tips of their cilia, which may be an apomorphic feature which indicates a close relationship between xenoturbellida, Nemertoder‐matida and Acoela.

The epidermal ciliary rootlets of Xenoturbella bocki (Xenoturbellida) revisited: new support for a possible kinship with the Acoelomorpha (Platyhelminthes)

The phylogenetic affinities of Xenoturbella remain highly debateable and a review of recent reports is given, together with a discussion of combinations of current phylogeny hypotheses.

⃛and molluscan embryogenesis

A study of oogenesis in X. bocki is reported, which contradicts earlier hypotheses as to the phylogeny of the animal and instead suggests a molluscan relationship close to or within the protobranch bivalves.

Ultrastructure of the subepidermal musculature of Xenoturbella bocki, the adelphotaxon of the Bilateria

Xenoturbella bocki is hypothesized to be the sister taxon of the Bilateria, the high-ranked taxon Xenoturbellida that lives on marine mud bottoms at a depth of 20–120 m and moves extremely slowly by ciliary gliding.

Xenoturbella 's molluscan relatives⃛

DNA sequence data are presented that place X. bocki within the protostome clade Eutrochozoa, and place it as the sister taxon of the Bilateria.

Combined large and small subunit ribosomal RNA phylogenies support a basal position of the acoelomorph flatworms

It is concluded that the Nemertodermatida and Acoela are basal bilaterians and, owing to their unique body plan and embryogenesis, should be recognized as a separate phylum, the Acoelomorpha.

Fine Structural Observations on the Extracellular Matrix (ECM) of Xenoturbella bocki Westblad, 1949

Previous indications of distinct similarities between certain characteristics of the epidermis and the SMC present in both enteropneusts and in Xenoturbella are strengthened.

Fine Structure and Function of Pharynx Cilia in Glossobalanus minutus Kowalewsky (Enteropneusta)

A model for mucus and water currents through gill slits is postulated and a ciliary specialization can be found in order to move a determinate substance, i.e. mucus or water.

Changes in mitochondrial genetic codes as phylogenetic characters: two examples from the flatworms.

A rapid computerized method for analyzing genetic codes is developed and demonstrated the wide phylogenetic distribution of the standard invertebrate code as well as confirming already known metazoan deviations from it (ascidian, vertebrate, echinoderm/hemichordate).
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