TY - JOUR
T1 - Evolutionary modification of specification for the endomesoderm in the direct developing echinoid Peronella japonica
T2 - Loss of the endomesoderm-inducing signal originating from micromeres
AU - Iijima, Minoru
AU - Ishizuka, Yasuhiro
AU - Nakajima, Yoko
AU - Amemiya, Shonan
AU - Minokawa, Takuya
N1 - Funding Information:
Acknowledgments We thank the members of the Misaki Marine Biological Station of the University of Tokyo and the Noto Marine Laboratory of Kanazawa University for supplying the animals. Many thanks are due to Dr. Masaaki Yamaguchi and all of the members of his laboratory for invaluable discussion and their help in animal collection. This study was partially supported by a “Grant-in-Aid for Young Scientists” (18770191) from the Ministry of Education, Culture, Sports, Science, and Technology of Japan, a Narishige Zoological Science Award, and a research grant from the graduate school of life sciences, Tohoku University, to T.M.
PY - 2009
Y1 - 2009
N2 - We investigated the inductive signals originating from the vegetal blastomeres of embryos of the sand dollar Peronella japonica, which is the only direct developing echinoid species that forms micromeres. To investigate the inductive signals, three different kinds of experimental embryos were produced: micromere-less embryos, in which all micromeres were removed at the 16-cell stage; chimeric embryos produced by an animal cap (eight mesomeres) recombined with a micromere quartet isolated from a 16-cell stage embryo; and chimeric embryos produced by an animal cap recombined with a macromere-derived layer, the veg1 or veg2 layer, isolated from a 64-cell stage embryo. Novel findings obtained from this study of the development of these embryos are as follows. Micromeres lack signals for endomesoderm specification, but are the origin of a signal establishing the oral-aboral (O-Ab) axis. Some non-micromere blastomeres, as well as micromeres, have the potential to form larval skeletons. Macromere descendants have endomesoderm-inducing potential. Based on these results, we propose the following scenario for the first step in the evolution of direct development in echinoids: micromeres lost the ability to send a signal endomesoderm induction so that the archenteron was formed autonomously by macromere descendants. The micromeres retained the ability to form larval spicules and to establish the O-Ab axis.
AB - We investigated the inductive signals originating from the vegetal blastomeres of embryos of the sand dollar Peronella japonica, which is the only direct developing echinoid species that forms micromeres. To investigate the inductive signals, three different kinds of experimental embryos were produced: micromere-less embryos, in which all micromeres were removed at the 16-cell stage; chimeric embryos produced by an animal cap (eight mesomeres) recombined with a micromere quartet isolated from a 16-cell stage embryo; and chimeric embryos produced by an animal cap recombined with a macromere-derived layer, the veg1 or veg2 layer, isolated from a 64-cell stage embryo. Novel findings obtained from this study of the development of these embryos are as follows. Micromeres lack signals for endomesoderm specification, but are the origin of a signal establishing the oral-aboral (O-Ab) axis. Some non-micromere blastomeres, as well as micromeres, have the potential to form larval skeletons. Macromere descendants have endomesoderm-inducing potential. Based on these results, we propose the following scenario for the first step in the evolution of direct development in echinoids: micromeres lost the ability to send a signal endomesoderm induction so that the archenteron was formed autonomously by macromere descendants. The micromeres retained the ability to form larval spicules and to establish the O-Ab axis.
KW - Direct development
KW - Echinoid
KW - Endomesoderm induction
KW - Evolution
KW - Micromeres
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U2 - 10.1007/s00427-009-0286-8
DO - 10.1007/s00427-009-0286-8
M3 - Article
C2 - 19437036
AN - SCOPUS:67349136324
VL - 219
SP - 235
EP - 247
JO - Wilhelm Roux's Archives of Developmental Biology
JF - Wilhelm Roux's Archives of Developmental Biology
SN - 0949-944X
IS - 5
ER -