The discovery of the primitive 'ciliate' on Antarctica is extremely rare since most are soft-bodied and just dissolve when they die.
It was trapped in the cocoon recovered by scientists from an exposure of rock on 10,000ft high Timber Peak in the Eisenhower Range of mountains to the east of Earth's southernmost continent, the 'Daily Mail' reported.
The microbe looks like a teardrop and its horseshoe-shaped main body is still discernible under the microscope.
After initial secretion the solidifying cocoon wall has the potential to ensnare and preserve microorganisms in a way comparable to plant resin.
These hairy microbes are part of a large group of microorganisms called Ciliophora that are common in water and comprise over 8,000 species.
They are single cells and the hairs - or 'cilia' - are how they propel themselves through the water.
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When leeches - a type of segmented worm - bear fertilised eggs they will secrete a cocoon from their glands that fully encases their body to lay them.
Once the cocoon has been secreted the leech will deposit the eggs and extricate itself. The eggs are then protected by the parent until they are ready to hatch.
It was a member of a family of organisms known as Vorticella - stalked, bell-shaped ciliates still abundant today in freshwater ponds and streams.
"The evolutionary history of the Ciliophora remains poorly understood - largely because most ciliates are soft-bodied organisms, which-like any other organisms that lack hard parts such as bones, shells, or wood - can become fossilised only under exceptional circumstances," said evolutionary biologist Dr Thomas Taylor, of Kansas University.
"Occasionally, however, exceptional fossil deposits that preserve soft-bodied organisms provide a rare glimpse of the true biodiversity during past periods of Earth history," Taylor said.
He said the discovery of the microbe also highlights the potential of clitellate (worm) cocoons as microscopic "conservation traps" comparable to amber.
The findings were described in Proceedings of the National Academy of Sciences.