Xenoturbella is a deuterostome that eats molluscs

ABSTRACT _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

flatworms1. Subsequent authors considered it variously as related to hemichordates and echinoderms owing to similarities of nerve net and epidermal ultrastructure2,3, to acoelomorph

flatworms based on body plan and ciliary ultrastructure4,5,6 (also shared by hemichordates7), or as among the most primitive of Bilateria8. In 1997 two papers seemed to solve this

uncertainty: molecular phylogenetic analyses9 placed _Xenoturbella_ within the bivalve molluscs, and eggs and larvae resembling those of bivalves were found within specimens of

_Xenoturbella_10,11. This molluscan origin implies that all bivalve characters are lost during a radical metamorphosis into the adult _Xenoturbella_. Here, using data from three genes, we

show that the samples in these studies were contaminated by bivalve embryos eaten by _Xenoturbella_ and that _Xenoturbella_ is in fact a deuterostome related to hemichordates and

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CAS  Google Scholar  Download references ACKNOWLEDGEMENTS We thank M. Akam and R. Jenner for comments on the manuscript, I. Ruiz Trillo for sharing unpublished results, and the scientists of

Kristineberg Marine Station for help in sample collection. We are grateful for support from the Wellcome Trust to M.J.T. and to D.T.J.L. AUTHOR INFORMATION AUTHORS AND AFFILIATIONS *

University Museum of Zoology, Department of Zoology, Downing Street, CB2 3EJ, Cambridge, UK Sarah J. Bourlat & Maximilian J. Telford * Zoological Museum (University of Copenhagen),

Universitetsparken 15, DK-2100, Copenhagen, Denmark Claus Nielsen * Department of Zoology, The Natural History Museum, Cromwell Road, SW7 5BD, London, UK Anne E. Lockyer & D. Timothy J.

Littlewood Authors * Sarah J. Bourlat View author publications You can also search for this author inPubMed Google Scholar * Claus Nielsen View author publications You can also search for

this author inPubMed Google Scholar * Anne E. Lockyer View author publications You can also search for this author inPubMed Google Scholar * D. Timothy J. Littlewood View author publications

You can also search for this author inPubMed Google Scholar * Maximilian J. Telford View author publications You can also search for this author inPubMed Google Scholar CORRESPONDING AUTHOR

Correspondence to Maximilian J. Telford. ETHICS DECLARATIONS COMPETING INTERESTS The authors declare that they have no competing financial interests. SUPPLEMENTARY INFORMATION SUPPLEMENTARY

INFORMATION: FIGURES AND TABLES (PDF 1264 KB) RIGHTS AND PERMISSIONS Reprints and permissions ABOUT THIS ARTICLE CITE THIS ARTICLE Bourlat, S., Nielsen, C., Lockyer, A. _et al._

_Xenoturbella_ is a deuterostome that eats molluscs. _Nature_ 424, 925–928 (2003). https://doi.org/10.1038/nature01851 Download citation * Received: 28 February 2003 * Accepted: 09 June 2003

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