Six Nasa astronauts are preparing to blast off into space on Shuttle Atlantis alongside some bizarre British guests — 4,000 microscopic worms.

The tiny creatures, dubbed wormonauts, are flying into space to help scientists better understand the effects of zero gravity on human muscles.

Known simply as Caenorhabditis elegans (C. elegans), they share up to 80 percent of their genetic material with humans and have been hailed a "perfect subtitute."

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Muscle wasting is a major problem for astronauts posted on long missions in space, where the lack of gravity means muscles are not exercised properly. The worms will be exposed to a new drug that reduces the effect of muscle degradation in cancer patients.

Scientists from Nottingham University's Institute of Clinical Research will examine the creatures on their return to see if the drug has any effect in space.

The worms will spend 11 days in orbit and will travel 4.5 million miles. While in space they will be taken to the International Space Station, where the primary research will be carried out in a Japanese experiment module called Kibo.

They will then be frozen before being flown back to earth for examination. Dr Szewczyk, from Nottingham University, said: "We can learn things in space that we would not be able to learn on earth. If we can identify what causes the body to react in certain ways in space we establish new pathways for research back on earth."

Dr Szewczyk’s C. elegans made news in 2003 when they survived the Space Shuttle Columbia disaster. Living in petri dishes and enclosed in aluminium canisters, the worms survived re-entry and impact on the ground and were recovered weeks later.