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An aboral‐dorsalization hypothesis for chordate origin
Author(s) -
Satoh Nori
Publication year - 2008
Publication title -
genesis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.093
H-Index - 110
eISSN - 1526-968X
pISSN - 1526-954X
DOI - 10.1002/dvg.20416
Subject(s) - chordate , notochord , biology , deuterostome , body plan , echinoderm , tadpole (physics) , neural tube , anatomy , vertebrate , evolutionary biology , embryo , embryogenesis , paleontology , microbiology and biotechnology , genetics , gene , physics , particle physics
Chordates originated from a common ancestor(s) shared with two other deuterostome groups, echinoderms and hemichordates, by creating a novel type of tadpole‐like larva, which was characterized by a dorsal hollow neural tube and notochord. Recent molecular phylogeny supports the notion that echinoderms and hemichordates form a clade named the Ambulacraria and that, among the chordates, cephalochordates are more basal than urochordates and vertebrates. An aboral‐dorsalization hypothesis is proposed to explain how the tadpole‐type larva evolved. Embryological comparison of cephalochordates with nonchordate deuterostomes suggests that, because of limited space on the oral side of the ancestral embryo, morphogenesis to form the neural tube and notochord occurred on the aboral side of the embryo. Namely, the dorsalization of the aboral side of the ancestral embryo may have been a key developmental event that led to the formation of the basic chordate body plan. genesis 46:614–622, 2008. © 2008 Wiley‐Liss, Inc.