Four fish flew aboard Columbia in 1994; eight babies hatched in space

In July 1994, four small medaka fish travelled into space as part of an experiment that tested whether fish could reproduce in microgravity. The experiment was carried out during the Second International Microgravity Laboratory (IML-2) mission aboard the Space Shuttle Columbia, or STS-65.The four medaka spent 15 days in space along with Japanese astronaut Chiaki Mukai. According to the Japan Aerospace Exploration Agency (JAXA), the experiment was proposed by Dr Ken-ichi Ijiri, who was then an associate professor at the University of Tokyo. The researchers identified 43 eggs during the experiment. The fishes became the first vertebrates known to lay eggs in space.More importantly, the eggs developed normally, and eight of them hatched while the fish were still in orbit. The young fish were later called 'space medaka'.Finding space-ready medakaTaking fish into space was not as simple as putting them inside a tank.