Insights into early animal evolution form the genome of the xenacoelomorph worm Xenoturbella bocki

• Published in: eLife 2024-08, Vol.13
• Main Authors: Schiffer, Philipp H, Natsidis, Paschalis, Leite, Daniel J, Robertson, Helen E, Lapraz, François, Marlétaz, Ferdinand, Fromm, Bastian, Baudry, Liam, Simpson, Fraser, Høye, Eirik, Zakrzewski, Anne C, Kapli, Paschalia, Hoff, Katharina J, Mueller, Steven, Marbouty, Martial, Marlow, Heather, Copley, Richard R, Koszul, Romain, Sarkies, Peter, Telford, Maximilian J
• Format: Article
• Language: English
• ISSN: 2050-084X

The evolutionary origins of Bilateria remain enigmatic. One of the more enduring proposals highlights similarities between a cnidarian-like planula larva and simple acoel-like flatworms. This idea is based in part on the view of the Xenacoelomorpha as an outgroup to all other bilaterians which are themselves designated the Nephrozoa (protostomes and deuterostomes). Genome data can provide important comparative data and help to understand the evolution and biology of enigmatic species better. Here we assemble and analyse the genome of the simple, marine xenacoelomorph , a key species for our understanding of early bilaterian evolution. Our highly contiguous genome assembly of has a size of ~111 Mbp in 18 chromosome like scaffolds, with repeat content and intron, exon and intergenic space comparable to other bilaterian invertebrates. We find to have a similar number of genes to other bilaterians and to have retained ancestral metazoan synteny. Key bilaterian signalling pathways are also largely complete and most bilaterian miRNAs are present. Overall, we conclude that has a complex genome typical of bilaterians, which does not reflect the apparent simplicity of its body plan that has been so important to proposals that the Xenacoelomorpha are the simple sister group of the rest of the Bilateria.