In this occasion, Multicellgenome lab tackles the unknown diversity among animals. In particular, Iñaki Ruiz-Trillo and colleagues analyze the diversity of a group of animals that are crucial to understand the origin of bilaterian symmetry: the Xenacoelomorpha, a group of morphologically simple worms that are known to occupy a pivotal phylogenetic position between non-bilaterian and bilaterian animals.

The transition from non-bilaterian to bilaterians is considered a major step in animal evolution, since the bilaterian symmetry provided more complex body plans and most of the extant animal diversity (only 3-4 animal phyla are non-bilaterian). Thus, to better understand this transition, IBE researchers analyzed, using molecular data from DNA barcoding projects, the marine diversity of the Xenacoelomorpha.

Their results show that one group of xenacoelomorphs, the acoels, have a higher diversity than previously known, with many unknown taxa still to be described. These include many species living in planktonic habitats, an habitat that was thought to have few acoel species. They also report a novel acoel  lineage, present in deep-sea environments, that represent the earliest-branching acoel clade, and thus, key to understand the last acoel ancestor. Overall, these data suggest there is a need to sample deep-sea habitats if we want to better understand animal diversity.

Reference Article: Arroyo, A.S.; López-Escardó, D.; de Vargas, C.; and Ruiz-Trillo, I. (2016). Hidden diversity of Acoelomorpha revealed through metabarcoding. Biology Letters 12 20160674; DOI: 10.1098/rsbl.2016.0674.