Fish In Space

Possibly one of the lesser known facts about fish is their claim to have 'boldly gone where no man has been before'. The notion of sending animals into space originally only served to test the survivability of spaceflight, before manned space missions were attempted. Once this was established, animals have been widely flown to investigate various biological processes along with the effects microgravity and space flight might have on them.

It first started when the limited supply of captured German V-2 rockets led to the U.S. use of high-altitude balloon launches carrying, amongst other species, the humble Goldfish (Carassius auratus) to heights of up to 144,000 feet. These high-altitude balloon flights from 1947-1960 tested radiation exposure, physiological response, life support and recovery systems. 

Skylab 3 (the second manned mission to the first American space station, Skylab, in 1973) carried the first fish in space; a Mummichog. The Mummichog (Fundulus heteroclitus) is a small killifish found in the eastern United States. Also known as mummies, gudgeons, and mud minnows, these fish are found in brackish and coastal waters including estuaries and salt marshes along the eastern seaboard of the United States, as well as the Atlantic coast of Canada. It is noted for its hardiness and ability to tolerate highly variable salinity, temperature fluctuations (from 6 °C to 35 °C), and for its ability to withstand very low oxygen levels, a wide variety of toxins, and survive in heavily polluted ecosystems. The mummichog was therefore thought to be the perfect subject for space flight. Mummichog were also flown by the U.S. on the Apollo-Soyuz joint mission, launched July 15, 1975 and several Soviet Bion program missions which consisted of satellites with biological cargoes. Subsequently, Salyut 5, launched on June 22, 1976, carried a different fish species; a Zebra Danio (Danio rerio).

During the1990s the U.S. dramatically expanded the number of species by carrying Medaka (Japanese rice fish: Oryzias latipes), Oyster Toadfish (Opsanus tau) and Swordtails (Xiphophorus helleri) as well as brine shrimp (Artemia salina), sea urchins, and jellyfish aboard Space Shuttle flights. 

In 2008, German researchers launched a rocket carrying 72 small cichlids on a brief space flight to study motion sickness. The fish were in an unmanned rocket that blasted off from a launch pad in northern Sweden and were filmed as they swam around weightlessly in small aquariums during the 10-minute space flight. The German team subsequently studied the video to see if some of the fish swam in circles because that is what fish do when they experience motion sickness. It was hoped that the experiment can help shed light on why some people experience motion sickness while others do not, because the mechanisms involved are similar for both fish and humans. The cichlids selected for this experiment where once again chosen because of appearing to easily cope with the stress of space flight.

More recently, in October 2012, 32 Medaka fish were delivered to the International Space Station by Soyuz TMA-06M. These fish are part of an experiment to study how fish adapt to the absence of gravity where the astronauts aboard the outpost will monitor changes in the fish as they live in orbit. The fish will live inside a space-age fish tank, called the Aquatic Habitat in the Kibo module, which was delivered to the space station on an earlier flight. Scientists are particularly interested in how the skeletal systems of fish change in the near weightless environment aboard the space station. Again, experiments such as the one with Medaka fish do not hold potential benefits for only space-flyers. The results of these types of studies can have far-reaching effects on Earth too (e.g. osteoporosis: 'brittle bones'). The lessons learned from studying the skeletal systems of fish in space can inform scientists on the ground about how bones degrade over time here on Earth.