Thousands of microscopic worms are taking to the skies as part of a space mission, a university said yesterday.

The worms were on board when the Space Shuttle Atlantis was launched from Cape Canaveral yesterday.

The unexpected astronauts will help experts in human physiology at the University of Nottingham understand more about what triggers the body to build and lose muscle.

The worms are bound for the Japanese Experiment Module "Kibo" on the International Space Station (ISS) where they will experience the same weightless conditions which can cause dramatic muscle loss in astronauts.

The Kibo lab makes use of the weightless conditions in orbit for the study of biomedicine and material sciences.

The worms are used by Dr Nathaniel Szewczyk, from the university's Institute of Clinical Research in Derby, UK, to study the signals that control muscle protein degradation.

He uses the microscopic worm Caenorhabditis elegans (C. elegans), because they are the perfect substitute for studying long term changes in human physiology - suffering from muscle loss under many of the same conditions that people do.

Muscle loss, or muscle atrophy, is one of the major health concerns for astronauts.

The research is also hoped to help scientists understand more about the condition which also affects the bedridden, people with muscular dystrophy and diabetes, people immobilised by casts and the elderly.

The worms, traced back to a rubbish dump in Bristol, often feed on bacteria that develop on decaying vegetable matter.

Their predecessors made news in 2003 when they survived the Space Shuttle Columbia disaster, including re-entry and impact, and were recovered weeks after the disaster.

Dr Szewczyk, who has carried out three previous space worm missions, is working with Professor Atsushi Higashitani from Tohoku University, Sendai, Japan.

Professor Higashitani is the Principal Investigator of the CERISE (C. Elegans RNAi In Space Experiment) payload and will be based in Florida during the flight to co-ordinate the payload's experiments.

Dr Szewczyk 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."

C. elegans was the first multi-cellular organism to have its genetic structure completely mapped and many of its 20,000 genes perform the same functions as those in humans.