Shuhai Xaio – Parapandorina

Video:


 

Cube Section Video

parapandorina inside from Web Master on Vimeo.A cube section video of the fossil.

 

Plane Section Video

parapandorina recon new slice movie from Web Master on Vimeo.

A video in which a planar section has been taken of the fossil to expose the cell walls on two sides.

 

Axial Section Movie

parapandorina recon bin4 movie1 from Web Master on Vimeo.

A clip showing the axial slices of the fossil from bottom to top.







Scanner Settings
Machine Xradia microXCT
Binning
2
Source Setting
50 kv, 160 µA
Source Distance
23 mm
Detector Distance 9 mm
Pixel Size
.9682 µm
FOV .954 mm
Magnification 20.093 X
Exposure Time 6 s
Image Size 985 X 985


Summary

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.

Subject

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

 

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