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Science 16 June 2006:
Vol. 312. no. 5780, pp. 1644 - 1646
DOI: 10.1126/science.1125964
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Reports

Phosphatized Polar Lobe-Forming Embryos from the Precambrian of Southwest China

Jun-Yuan Chen,1* David J. Bottjer,2 Eric H. Davidson,3 Stephen Q. Dornbos,4 Xiang Gao,1 Yong-Hua Yang,1 Chia-Wei Li,5 Gang Li,6 Xiu-Qiang Wang,1 Ding-Chang Xian,6 Hung-Jen Wu,5 Yeu-Kuang Hwu,7 Paul Tafforeau8,9

In developing embryos of some extant spiralian animals, polar lobe formation is one of the symmetry-breaking mechanisms for segregation of maternal cytoplasmic substances to certain blastomeres and not others. Polar lobe formation leads to unique early cleavage morphologies that include trilobed, J-shaped, and five-lobed structures. Fossil embryos similar to modern lobeforming embryos are recognized from the Precambrian Doushantuo Formation phosphates, Weng'an, Guizhou Province, China. These embryos are abundant and form a developmental sequence comparable to different developing stages observed in lobe-forming embryos of extant spiralians. These data imply that lobe formation is an evolutionarily ancient process of embryonic specification.

1 Nanjing Institute of Geology and Paleontology, Institute of Evo/Developmental Biology, and State Key Laboratory of Pharmaceutical Biotechnology, Nanjing University, Nanjing 210093, China.
2 Department of Earth Sciences, University of Southern California, Los Angeles, CA 90089, USA.
3 Division of Biology, 156-29, California Institute of Technology, Pasadena, CA 91125, USA.
4 Department of Geosciences, University of Wisconsin, Milwaukee, WI 53201, USA.
5 Department of Life Science, National Tsing Hua University, Hsinchu 300, Taiwan, China.
6 Institute of High Energy Physics, Beijing 100049, China.
7 Institute of Physics, Academia Sinica, Taipei, Taiwan, China.
8 European Synchrotron Radiation Facility, F-38043 Grenoble, France.
9 Laboratoire de Géobiologie, Biochronologie et Paléontologie Humaine, UMR CNRS 6046, F-86022 Poitiers, France.

* To whom correspondence should be addressed. E-mail: chenjy{at}nju.edu.cn, chenjunyuan{at}163.net

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THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
Complex embryos displaying bilaterian characters from Precambrian Doushantuo phosphate deposits, Weng'an, Guizhou, China.
J.-Y. Chen, D. J. Bottjer, G. Li, M. G. Hadfield, F. Gao, A. R. Cameron, C.-Y. Zhang, D.-C. Xian, P. Tafforeau, X. Liao, et al. (2009)
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Cellular and Subcellular Structure of Neoproterozoic Animal Embryos.
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