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Insights from diploblasts; the evolution of mesoderm and muscle
Author(s) -
Burton Patrick Michael
Publication year - 2007
Publication title -
journal of experimental zoology part b: molecular and developmental evolution
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.823
H-Index - 63
eISSN - 1552-5015
pISSN - 1552-5007
DOI - 10.1002/jez.b.21150
Subject(s) - mesoderm , ectoderm , biology , endoderm , ancestor , germ layer , anatomy , most recent common ancestor , cnidaria , evolutionary biology , genetics , embryo , phylogenetics , embryogenesis , embryonic stem cell , ecology , history , archaeology , coral , induced pluripotent stem cell , gene
The origin of both mesoderm and muscle are central questions in metazoan evolution. The majority of metazoan phyla are triploblasts, possessing three discrete germ layers. Attention has therefore been focused on two outgroups to triploblasts, Cnidaria and Ctenophora. Modern texts describe these taxa as diploblasts, lacking a mesodermal germ layer. However, some members of Medusozoa, one of two subphyla within Cnidaria, possess tissue independent of either the ectoderm or endoderm referred to as the entocodon. Furthermore, members of both Cnidaria and Ctenophora have been described as possessing striated muscle, a mesodermal derivative. While it is widely accepted that the ancestor of Eumetazoa was diploblastic, homology of the entocodon and mesoderm as well as striated muscle within Eumetazoa has been suggested. This implies a potential triploblastic ancestor of Eumetazoa possessing striated muscle. In the following review, I examine the evidence for homology of both muscle and mesoderm. Current data support a diploblastic ancestor of cnidarians, ctenophores, and triploblasts lacking striated muscle. J. Exp. Zool. (Mol. Dev. Evol.) 310B:5–14, 2008 . © 2007 Wiley‐Liss, Inc.