A colony of microscopic worms, Caenorhabditis elegans (C elegans), that are biologically very similar to humans, have been reported to have survived a stint in space for finding out ways and means of survival of the human body if taken to another planet.
Around 4,000 of these worms were taken to the International Space Station in December 2006, and they were able develop from egg to adulthood and produce progeny in space, exactly the way they do on earth.
C. elegans are known to be the very first multi-cellular organism to have its genetic structure entirely mapped. Various of its 20,000 genes execute the same functions just like human beings. About 2,000 of these genes are considered very important in promoting muscle function and 50-60% of these have very apparent human counterparts.