Model Animals for Space Experiments - Species Flown in the Past and Candidate Animals for the Future Experiments

Abstract

Nearly 50 multicelluar animal species have ever been flown on the near earth orbit or further. Animals used in space experiments range from Primates to Cnidaria. Widely used laboratory animals on the ground, such as rats and fruit flies, are frequently flown species. Mice, however, seem less popular in space experiments, probably because of their relatively poor resistance to the stressful space environment. To keep rodents onboard the space craft in a health state requires tremendous efforts. Moreover, the use of rodents onboard the International Space Station (ISS) has become extremely difficult, due to the cancellation of the Centrifuge facility. Rearing fish in space, on the other hand, is easier than to keep rodents, since their waste excretions are borne by the water flow and can be effectively removed by filtering. Fish are suitable model for the studies on development, radiation effects and vestibular functions. Among fish, Medaka (Oryzias latipes) will be the most useful species for space experiments, with the inventory of inbred and mutant strains, their genome sequence data, and the established gene knockout technologies. Medaka together with established small laboratory animals, such as C. elegans, are most promising species for the experiments onboard the ISS. Other unique groups of animals in space experiment are those inhabit in the arid area. These animals, such as Mongolian Gerbil (Meriones unguiculatus), generally require few drinking water and produce little amount of waste. This enables flight hardware being simpler. Although the lack of their genome sequence data is a big drawback, they are useful for space experiments, especially for those utilizing recoverable capsule satellites.