Acantocephala

This project aims at obtaining new genomic data in order to improve the understanding of Lophotrochozoa phylogeny. Although these animals display the greatest diversity of the three major bilaterian clades, adequate genomic data are scarce for many phyla whose affinities have not been unambiguously resolved yet. Hence, several very important nodes in the evolutionary history of Protostomes are still poorly resolved. EST sequencing in Acanthocephala, a phylum for which little information is available, will enrich the taxonomic and gene sampling for phylogenomics, population genetics and comparative genomics.

Molecular data have significantly changed our view of the metazoan phylogeny and recent phylogenomics analyses have supported the Lophotrochozoa and Ecdysozoa [1] clades. Less satisfactory, analyses could not resolve the Syndermata relationships and Platyzoa hypothesis was either corroborated or contradicted [2]. Hence, the understanding of Lophotrochozoa relationships requires critical evaluation of Platyzoa. The P. laevis EST sequences generated by the Genoscope will produce a large number of new molecular markers to answer this question.

We selected the species Pomphorhynchus laevis for two reasons:

  adult specimens can be easily collected in the gut of Barbus barbus, a common fish of the French continental waters.

  a cDNA library can be established from a single specimen.

Because of its original characteristics, Acanthocephala is a useful model for approaching questions of speciation. The sequencing of ESTs associated with a PCR survey on several populations will provide a good starting material for population genetic studies. Gene phylogenies could identify cryptic species within P. laevis, corresponding to independent lineages specialized on different host species and/or different microenvironments in the same host. Homology comparison will also allow the identification of genes under positive selection, which is expected to play role in host adaptation.

Contact: Julie Poulain (Genoscope) - Yvan Perez (Institut Méditerranéen d’Ecologie et de Paléoécologie)