The phylogenetic position of ctenophores and the origin(s) of nervous systems
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- 作者：Gáspár Jékely ; Jordi Paps ; Claus Nielsen
- 关键词：Ctenophore ; Nervous system evolution ; Cnidarian ; Sponge ; Trichoplax ; Neuropeptide ; Metazoan phylogeny ; DEG/ENaC channels ; MicroRNA ; Ciliary photoreceptor
- 刊名：EvoDevo
- 出版年：2015
- 出版时间：December 2015
- 年：2015
- 卷：6
- 期：1
- 全文大小：2,782 KB
- 刊物主题：Developmental Biology; Evolutionary Biology; Zoology; Paleontology; Plant Genetics & Genomics;
- 出版者：BioMed Central
- ISSN：2041-9139
文摘
Ctenophores have traditionally been treated as eumetazoans, but some recent whole genome studies have revived the idea that they are, rather, the sister group to all other metazoans. This deep branching position implies either that nervous systems have evolved twice, in Ctenophora and in Eumetazoa, or that an ancestral metazoan nervous system has been lost in sponges and placozoans. We caution, however, that phylogenetic-tree construction artifacts may have placed ctenophores too deep in the metazoan tree. We discuss nervous system origins under these alternative phylogenies and in light of comparative data of ctenophore and eumetazoan nervous systems. We argue that characters like neuropeptide signaling, ciliary photoreceptors, gap junctions and presynaptic molecules are consistent with a shared ancestry of nervous systems. However, if ctenophores are the sister group to all other metazoans, this ancestral nervous system was likely very simple. Further studies are needed to resolve the deep phylogeny of metazoans and to have a better understanding of the early steps of nervous system evolution.