Molecular Genetics of Protochordates (Goog)
"We indeed produce a novel scenario for the history ... with a ProtoHox cluster comprising only two anterior genes, and considerable divergence of cnidarians and bilaterians after their split."
New scenario of Hox/ParaHox cluster genesis inferred from the comparison of bilaterian and cnidarian gene complements.
Mapping the Genome of a Model Protochordate (Goog)
"BOTRYLLUS schlosseri is a colonial ascidian which inhabits shallow subtidal marine habitats around the world. As protochordates, these organisms occupy a key phylogenetic position in the evolution of vertebrates: protochordates are likely the direct predecessors of the chordate line... The product of ascidian sexual reproduction is a free swimming tadpole with a chordate body plan, including a notochord, dorsal hollow nerve tube and segmented musculature. Following hatching from the mother colony, the tadpole swims to a nearby surface, attaches to the substratum and metamorphoses to an invertebrate form. In the colonial ascidians such as B. schlosseri, metamorphosis is followed by a budding process which gives rise to a large colony of asexually derived, genetically identical offspring united by a common vascular network."