Phylogenetic position of Hydra. A) The phylogenetic tree of opisthokonts was drawn according to [12,13]. Together with ctenophores, cnidarians form the Coelenterate superphylum. Coelenterates together with bilaterians constitute Eumetazoa, whereas porifers (sponges) occupy a sister group position within Metazoa. Dates are expressed in million years (my) according to . LCA: Last Common Ancestor. B) Anatomy of the adult Hydra polyp. Scale bar: 400 μm. C) Phylogenetic tree of the various Hydra species drawn according to [15,16]. Genome-predicted transcriptomes are available from H. magnipapillata (Hm) , a RNAseq-454 transcriptome was produced from H. vulgaris AEP (AEP)  and this study presents a RNAseq Illumina-454 transcriptome from H. vulgaris Basel (Hv).
Wenger and Galliot BMC Genomics 2013 14:204 doi:10.1186/1471-2164-14-204