Servicio de Información Comunitario sobre Investigación y Desarrollo - CORDIS


XENOTURBELLA Informe resumido

Project ID: 322790
Financiado con arreglo a: FP7-IDEAS-ERC
País: United Kingdom

Mid-Term Report Summary - XENOTURBELLA (The evolution of simplicity: comparative morphology, embryology and genomics of Xenacoelomorpha, the fourth phylum of deuterostome.)

We are studying a recently identified phylum of animals called the xenacoelomorphs. A phylum is defined as having a distinct body plan examples of phyla include arthropods, molluscs and chordates. All members of the Xenacoelomorpha phylum are marine worms and most are tiny - less than a millimetre in length. They have been known about for many years but were generally misclassified and wrongly associated with the flatworms (phylum Platyhelminthes). Their true position within the evolutionary tree of animals is still controversial. The two possibilities being first that these simple worms represent an early diverging branch within the animals and that their simplicity relative to other animals is due to their having evolved early. The second possibility is that these simple worms are members of the deuterostomes - a more complex group of animals that include chordates (such as vertebrates) and echinoderms (e.g. starfish). If this latter evolutionary relationship proves correct it suggests that these simple worms derive from a complex ancestor and must therefore have lost complexity over evolutionary time. We have built a large data set of genetic data (over a thousand genes from 60 species of animals) to test this difficult to resolve phylogenetic question.

We are also interested in characterising the genomes of these animals - what genes do they possess? Have they lost genes in becoming more simple and if so can we discern meaningful patterns in the losses? We have sequenced transcriptomes from several of these species and are currently sequencing their complete genomes.

Finally we want to discern just how simple these worms really are. As an example they are thought to lack nephrocytes (cells involved in filtration as found in vertebrate kidneys). We have looked for genes with a conserved function in nephrocyte biology (present in vertebrates and insects e.g.). We can find most of these genes in xenacoelomorphs and are currently finding out which cells express these genes and what the function of these genes is in xenacoelomorphs. To do this we are developing protocols for examining gene expression and will develop methods to disrupt the normal function of these genes.

More generally we are carefully characterising the morphology of these animals using techniques such as scanning and transmission electron microscopy, thin sectioning, whole mount and thin section in situ hybridisation (to visualise gene expression) and light sheet microscopy. Our aim is to understand these worms better in terms of their genetics and their morphology in order to compare them to other better known animal models. These comparisons will tell us about the evolution of this little known group of animals and promises broader insights into animal evolution.

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United Kingdom
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