The mouth and anus are not connected in the development of the embryo as earlier thought, shows a Norwegian ground-breaking study.

Animals often form either the mouth or the anus from an opening that appears in the early embryo, which is called the blastopore.

For instance, starfish develop the anus from the blastopore, but earthworms form the mouth out of it. How this happens has not been clear until now.

"Our findings demonstrate that whether the blastopore forms the mouth or the anus is a consequence of how each embryo is organized during early development. It is not a predefined attribute of the species, as previously thought," says postdoctoral researcher Jose Maria Martin-Duran, at the Hejnol Group at Sars Centre at the Department of Biology, University of Bergen (UiB).

"One of the most important conclusions of our work is that there is no necessary association of the mouth and the anus with the embryonic blastopore," says Martin-Duran.