during what stage in its life cycle does a sponge move

Thus, among the three contentious ‘basal’ clades, sponges, which likely retained the organization of the earliest metazoans, can be expected to provide significant clues towards understanding the origin of the complex bilaterian body plans 4. Conversely, Trichoplax adhaerens, composed of only four cell types, appears to be secondarily simplified, as divergence of the placozoan lineage likely occurred after the divergence of sponges 14. Some analyses support basal position of the ctenophores, morphological complexity of which might be a result of independent evolution 6, 13. Several lines of evidence (morphology, molecular phylogenies, fossil record) suggest that the first multicellular animals had poriferan-grade body plans with choanoflagellate-like cells (choanocytes) used for water movement, food capture and digestion, but lacked key metazoan cell types, for example, nerves and muscles 7, 8, 9, 10, 11, 12. These results provide a framework for further studies aimed at deciphering ancestral developmental regulatory networks and their modifications during animal body plans evolution.Įlucidation of macroevolutionary transitions between animal body plans remains to be a major challenge in evolutionary biology 1, 2, 3, 4, additionally complicated by disputable branching order of metazoan lineages 5, 6. Similarity in developmental gene expression between sponges and eumetazoans, especially cnidarians, is consistent with Haeckel’s view that body plans of sponges and cnidarians are homologous. Genes involved in formation of the eumetazoan endomesoderm, such as β -catenin, Brachyury and Gata, as well as germline markers Vasa and Pl10, are expressed during formation and maintenance of choanoderm, the feeding epithelium of sponges. Here we show that many members of surprisingly numerous Wnt and Tgfβ gene families are expressed higher or uniquely in the adult apical end and the larval posterior end. We address the sponge-eumetazoan transition by analyzing expression of a broad range of eumetazoan developmental regulatory genes in Sycon ciliatum (Calcispongiae). Elucidation of macroevolutionary transitions between diverse animal body plans remains a major challenge in evolutionary biology.

During what stage in its life cycle does a sponge move