Four medaka fish flew aboard Columbia in 1994 to test whether vertebrates could reproduce without gravity; they laid 43 eggs and eight baby fish 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.