Abstract
Elucidation of macroevolutionary transitions between diverse animal body plans remains a major challenge in evolutionary biology. We address the sponge-eumetazoan transition by analyzing expression of a broad range of eumetazoan developmental regulatory genes in Sycon ciliatum (Calcispongiae). 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. 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. 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. These results provide a framework for further studies aimed at deciphering ancestral developmental regulatory networks and their modifications during animal body plans evolution.
Highlights
Elucidation of macroevolutionary transitions between diverse animal body plans remains a major challenge in evolutionary biology
Elucidation of macroevolutionary transitions between animal body plans remains to be a major challenge in evolutionary biology[1,2,3,4], complicated by disputable branching order of metazoan lineages[5,6]
Our results provide a framework for further studies aimed at deciphering ancestral developmental regulatory networks and their modifications that underlie animal body plans evolution
Summary
Elucidation of macroevolutionary transitions between diverse animal body plans remains a major challenge in evolutionary biology. 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 These results provide a framework for further studies aimed at deciphering ancestral developmental regulatory networks and their modifications during animal body plans evolution. While Haeckel[28,29] directly compared the adult sponge body plans with those of corals, this view does not receive much support currently One reason for such a discrepancy might be that Haeckel’s prime interests were calcareous sponges, many of which have asconoid or syconoid organization, at least superficially similar to cnidarian polyps: a columnar body composed of two epithelial layers with the inner layer serving a feeding function, and a single major opening (osculum) at the apical end. The developmental gene toolkit of sponges is surprisingly similar to the eumetazoan toolkit, information on its expression remains limited[4,7]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
