Phosphatized polar lobe-forming embryos from the Precambrian of southwest China |
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Authors: | Chen Jun-Yuan Bottjer David J Davidson Eric H Dornbos Stephen Q Gao Xiang Yang Yong-Hua Li Chia-Wei Li Gang Wang Xiu-Qiang Xian Ding-Chang Wu Hung-Jen Hwu Yeu-Kuang Tafforeau Paul |
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Institution: | Nanjing Institute of Geology and Paleontology, Institute of Evo/Developmental Biology, and State Key Laboratory of Pharmaceutical Biotechnology, Nanjing University, Nanjing 210093, China. chenjy@nju.edu.cn |
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Abstract: | 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. |
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