Scientists to send fish on rocket ride

STOCKHOLM (Reuters) - Scientists plan to launch 60 tiny fish on a zero gravity rocket ride from above the Arctic Circle on Monday to try to plumb the secrets of motion sickness.

Tomas Hedqvist, project manager for Sweden's Esrange Space Centre, said the baby cichlid fish will head 260 km (160 miles) into the air on an 11-metre (36-foot) two-stage rocket, where they will experience six minutes of weightlessness.

Experimenters Reinhard Hilbig and Ralf Anken of the University of Stuttgart-Hohenheim in Germany will train six video cameras on the fish, each of which will be housed in its own aquarium, to see how they react.

"Fish, when they get motion sick, begin tumbling around, swimming in circles and miss their balance," he said, adding that some fish do not suffer from motion sickness and seem to adapt quickly to a changed environment.

Some of the fish, which were flown from Germany to Sweden's far north in special aquariums, will be housed in a slowly turning centrifuge which will offer some gravity while others will be in a pure zero G state, Hedqvist said.

After the flight, the scientists will examine the video camera recordings as well as small balance organs -- called otoliths -- which exist naturally in the heads of each fish to work out what makes some sick and others not.

"People when they are aboard the space shuttle they have this space motion sickness also. Human beings have blood pressure up in the head when they are weightless and also bones get weak and muscles get small," Hedqvist said.

"They use fish since it's much easier to investigate on fish (than) human beings."

Earlier related experiments sent cichlid fish on parabolic plane rides -- which involve a steep ascent followed by a plunge -- but Hedqvist said these only offered 20-30 seconds of weightlessness and were too short for clear conclusions.

(Reporting by Sarah Edmonds; Editing by Caroline Drees)