The exact moment at which a 550 million year-old
cell began to divide has been captured in an exquisite 3D image.
The picture is one of a series taken by researchers
in 2006 while they were examining ancient fossil embryos from Guizhou
Province, China. At the time the specimens, described in the journal
Science, were the oldest known examples of fossil embryos, and they
served to shed light on the early evolution of complex life.
Scientists used an advanced x-ray technique to peer
inside the balls of cells to reveal the structures inside.
'We have been able to tease apart every structure,
geological or biological,' said Professor Phil Donoghue of the
University of Bristol in the UK and one of the team who worked on
the 162 pristine specimens.
The tiny fossils were part of the Doushantuo
Formation in Southern China, a limestone bed deposited between 635
and 551 million years ago which contains layers that are composed
almost entirely of fossil embryos.
The team behind the research believed that the fossils
were the developing offspring of extremely primitive sponge-like
creatures. To resolve the delicate internal structures, the scientists
used a technique known as microfocus x-ray computed tomography (microCT).
The method allowed the team to construct 3D images of the tiny fossils.
Computer software was then used to analyse individual cells.
'We digitally extracted each cell from the embryos
and then looked inside the cells,' said Shuhai Xiao of Virginia Tech
University in the US. Inside, the team found kidney-shaped structures
which they believed could be nuclei or other subcellular components.