The last Japanese re-supply mission to the I.S.S. carried an interesting item to be part of the Japanese Experiment Module. This is known as the Aquatic Habitat and it will house 32 Medaka fish, also known as Zebrafish. These fish will be flown into space in October as part of the next crew cycle for the I.S.S. These fish were picked for their transparent bodies and because they have shown the ability to reproduce in space in 3 previous short duration space shuttle missions (STS-47, STS-65, and STS-90). This fishy experiment is designed to study the effects on the bones and muscles of the fish. As we have noted before, humans lose bone density and muscle strength on long duration space flights.
This new aquatic habitat has the ability to filter out wastes, while providing oxygen that the fish need to breathe. The first thing that the astronauts need to do is to inject oxygen into the tanks with a syringe. LED lights will be switched on and off to simulate daylight and nighttime conditions. Automatic feeding will take care of the regular dietary needs of the fish. The astronauts will then check on the fish regularly, taking notes on the bones, muscles, and internal organs of the fish. Another task to is track the laying of eggs, hatching, and growth of up to three generations of medaka fish. As the experiment is only designed to last 90 days, this will not be a permanent space fish outpost. It is also possible that successful breeding of space fish could result in long term space missions including fresh fish on their astronauts menus, which is good because fish are high in protein and long duration spaceflight may require astronauts to grow their own food.
While this isn’t the first space fish experiment, it is the longest. The fish will have about 700cc of water to live in, which is not much water but more than enough for these small fish. These are Japanese fish that live in gently flowing streams, ponds, and rice fields and have been studied by Japanese schoolchildren for years. Fish don’t seem to suffer from as much bone and muscle loss in space and we need to find out why. Hopefully, studying these fish will not only help understand biological effects of weightlessness on humans but also find cures for muscle and bone disease like osteoporosis that occur on Earth as well as in space.