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Nutritional endoderm: a way to breach the holoblastic–meroblastic barrier in tetrapods
Author(s) -
Elinson Richard P.
Publication year - 2008
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.21218
Subject(s) - endoderm , amniote , biology , yolk , zygote , cleavage (geology) , yolk sac , embryo , embryogenesis , microbiology and biotechnology , germ layer , anatomy , evolutionary biology , cellular differentiation , genetics , embryonic stem cell , fishery , paleontology , fracture (geology) , induced pluripotent stem cell , gene , vertebrate
The deceptively simple evolutionary transition from complete, holoblastic cleavage of the zygote to incomplete, meroblastic cleavage occurred only once in tetrapods, with the evolution of the amniote egg. By examining the development of a frog with large eggs, we identified a new tissue called the nutritional endoderm, which provides a possible intermediate step to breach the holoblastic–meroblastic barrier. Nutritional endoderm is divided into cells, but the cells disappear and do not contribute to tissues of the frog after the yolk is depleted. The complete loss of this yolk‐rich tissue raises the question as to what feature of early development requires cellularization of this endoderm. J. Exp. Zool. Mol. Dev. Evol. 312B:526–532, 2009 . © 2008 Wiley‐Liss, Inc.