BLOOMINGTON, Ind. -- Fossilized embryos predating the Cambrian Explosion by 10 million years provide evidence that early animals had already begun to adopt some of the structures and processes seen in today's embryos, say researchers from Indiana University Bloomington and nine other institutions in this week's Science. James Hagadorn of Amherst College led the multi-disciplinary international collaborative project.
The researchers from the U.S., U.K., China, Sweden, Switzerland and Australia report the first direct evidence that primitive animals 550 million years ago were capable of asynchronous cell division during embryonic development. Asynchronous cell division allows the formation of unique shapes.
"We're learning something about how the very earliest multicellular animals formed embryos and how the embryos developed," said IU Bloomington biologist Rudolf Raff, a coauthor of the report. "This gives us an enormous and entirely surprising look at half-a-billion-year-old embryos in the act of cleaving. What a window on the past. We've had no prior idea what they might have done."
The researchers also believe they've identified specialized structures inside the cells, such as bubble-like vesicles that the cells might have used to transport, store or metabolize molecules. Slight aberrations during the fossilization of dead embryonic cells even reveal what appear to be dividing nuclei. It was assumed such structures existed in early animals, but until now, no known fossils of the structures existed.
The scientists procured 162 "relatively pristine" animal embryo fossils from the Doushantuo Formation of south central China. The embryos were still encased in a fertilization envelope, a protective husk that likely aided the preservation of the embryos long enough for fossilization to occur. To inspect the fossils' surfaces and even innards, the scientists used a bevy of imaging techniques, including X-ray computed tomogra
Contact: David Bricker