Parapandorina - 5/19/2010
Plane Section Video
Axial Section Movie
Researchers at Virginia Tech believe that this Parapandorina fossil is the oldest evidence of any animal life form. CT scanning was particularly useful in the analysis of this fossil because it offered a nondestructive means of seeing the fossil's subcellular structures. Other methods, such as the use of an electron microscope, required that layers be shaved off the fossil to reveal the cellular structures inside.
The fossil is from the 600 million year old Doushantuo formation in China.
Interpretations of the embryo vary, but Virginia Tech researchers believe that it is an animal embyro which would make it the earliest evidence of animal life on the planet. This specific embroyo has multiple cells with subcellular structures that can be revealed using filters on the CT machine's reconstruction algorithm.
About the Scan
The subject was mounted on a FIB needle, the tip of which is about 200 microns in diameter. The fossil was very fragile, making it very difficult to mount without breaking. The fragility of the fossil further attests to the advantages of using nondestructive CT scanning over other methods which destroy the subject and give no chance to repeat the imaging procedure.
Links and Literature
Hagadorn, J. W., S. Xiao, P. C. J. Donoghue, S. Bengtson, N. J. Gostling, M. Pawlowska, E. C. Raff, R. A. Raff, F. R. Turner, C. Yin, C. Zhou, X. Yuan, M. B. McFeely, M. Stampanoni, and K. H. Nealson, Cellular and subcellular structure of Neoproterozoic embryos. Science, 314: 291�294.
Dr. Xaio's website