Why Japanese Killifish are Calling the ISS ‘Home’
Tuesday, August 21st, 2012
by AJ Plunkett
The Medaka, or Japanese killifish, have the distinction of being the first vertebrates to mate and reproduce in space. If that weren’t enough, soon they will be answering the call of science again, producing offspring onboard the International Space Station in an experiment examining how radiation and microgravity in space affect multiple generations of a species.
To do so, a popular freshwater fish, the Medaka, will be kept in a special space aquarium recently delivered to the ISS aboard an unmanned Japanese cargo ship.
The space fish aquatic habitat. Credit: JAXA
The experiment is one of several that Japanese scientists have designed to examine how spending long periods in the microgravity of space can impact bone degradation, muscle atrophy, and biological development.
The findings could lead to improvements in health care on Earth, “especially for the aging society,” Nobuyoshi Fujimoto told NASA recently. Fujimoto is Associate Senior Engineer for the Space Environment Utilization Center of the Japanese Aerospace Exploration Agency, often referred to as ‘JAXA’.
While the aim of the experiments is to improve health on Earth, scientists hope the findings will also help researchers design radiation shielding for spacecraft intended for long-term space exploration.
Why the Medaka?
The Medaka are considered to be the best specimens to use in these experiments, in part because they are transparent, which allows for easier viewing of their internal organs, and in part because they breed so easily and quickly in microgravity.
Scientists are hoping for the fish to produce at least three sets of offspring during the 90-day experiment. Multiple generations will be “a first for fish in space,” Fujimoto said.
Space Mutations
Researchers will look for genetic mutations that might occur among the offspring, and will also mate male fish just returned from space with females kept on Earth to see how the space environment might have affected sperm.
The Medaka, or Oryzias latipes, are also ideal for this type of experiment because scientists already have the entire Medaka genome identified, making it easier to spot mutations.
Hearty Vertebrates
And, apparently, they just handle space really well. Other trips into space have shown that certain strains of Medaka don’t get space sick like other fish.
(Yes, fish do get seasick and space sick, just like humans, because both share a remarkably similar inner-ear structure. Humans get sick in space because it’s hard for the brain to tell the inner ear which way is up — in microgravity there is no up. Fish just show it a different way: they swim in circles.)
Space Habitat
The Aquatic Habitat feature two habitation chambers, automatic feeding, temperature control, LED lights to simulate day and night cycles, and a “stabilized area for oxygen that will enable fish to ‘peck’ air,” according to NASA information.
The aquarium was delivered aboard the Kounotori 3, the third unmanned cargo craft that Japan has sent up to the space station. It was snagged out of orbit and brought into dock by astronaut Akihiko Hoshide using the Space Station’s Canadarm. (Hoshide was the first JAXA astronaut to use the robotic arm.)
The fish will be housed in the largest of the experiment modules on the ISS, the Kibo Laboratory, which was one of the last modules of the Space Station installed. It was included in the project, in part, because of Japan’s success with various fish experiments aboard the Space Shuttle. Among the types of fish used in those experiments? Yep, you guessed it, the Medaka.
AJ Plunkett is a freelance writer in Virginia with experience in covering defense and aerospace industries as well as the military. AJ blogs via Contently.com.