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Mitochondrial genome sequence and gene order of Sipunculus nudus give additional support for an inclusion of Sipuncula into Annelida

Adina Mwinyi1, Achim Meyer2, Christoph Bleidorn3, Bernhard Lieb2, Thomas Bartolomaeus4 and Lars Podsiadlowski14*

Author Affiliations

1 Institut für Zoologie, Freie Universität Berlin, Koenigin-Luise-Str. 1-3, 14195 Berlin, Germany

2 Institut für Zoologie, Johannes Gutenberg Universität Mainz, Müllerweg 6, 55099 Mainz, Germany

3 Institut für Biochemie und Biologie, Universität Potsdam, Karl-Liebknecht-Str. 24-25, 14476 Golm, Germany

4 Institut für Evoilutionsbiologie & Ökologie, Universität Bonn, An der Immenburg 1, 53121 Bonn, Germany

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BMC Genomics 2009, 10:27  doi:10.1186/1471-2164-10-27

Published: 16 January 2009



Mitochondrial genomes are a valuable source of data for analysing phylogenetic relationships. Besides sequence information, mitochondrial gene order may add phylogenetically useful information, too. Sipuncula are unsegmented marine worms, traditionally placed in their own phylum. Recent molecular and morphological findings suggest a close affinity to the segmented Annelida.


The first complete mitochondrial genome of a member of Sipuncula, Sipunculus nudus, is presented. All 37 genes characteristic for metazoan mtDNA were detected and are encoded on the same strand. The mitochondrial gene order (protein-coding and ribosomal RNA genes) resembles that of annelids, but shows several derivations so far found only in Sipuncula. Sequence based phylogenetic analysis of mitochondrial protein-coding genes results in significant bootstrap support for Annelida sensu lato, combining Annelida together with Sipuncula, Echiura, Pogonophora and Myzostomida.


The mitochondrial sequence data support a close relationship of Annelida and Sipuncula. Also the most parsimonious explanation of changes in gene order favours a derivation from the annelid gene order. These results complement findings from recent phylogenetic analyses of nuclear encoded genes as well as a report of a segmental neural patterning in Sipuncula.