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DEVELOPMENT OF AQUATIC HABITAT FOR BIOLOGICAL RESEARCH IN SPACE.  W. Nishikawa,¹ T. Ochiai,¹ N. Ishioka,¹ and T. Sakimura².  ¹National Space Development Agency of Japan, and ²Mitsubishi Heavy Industries, Ltd.

  Small fish and amphibians become valuable experimental animals in biological and medical sciences.  Embryos are easy to manipulate and observe, and they posses full basic vertebrate features.  Reproductive efficiency and short life cycle are also advantageous.  Furthermore, small aquatic animals are less demanding in space experiments than rodents.  We already established a system for fish spawning and flew on STS-65. 
  We are now studying the next-generation aquatic animal experiment facility (AQH) for both Space Shuttle and Space Station use.  The AQH will be capable of supporting 90-day experiments by life-support, breeding, specimen monitoring, and specimen sampling capability.  The AQH will accommodate three generations of medaka, zebrafish and maintain Xenopus from egg through metamorphosis.  We developed the Bread Board Model (BBM) and perform the compatibility test by medaka.
   We will introduce the concept of the AQH, the BBM, and the results of breeding tests with medaka using a prototype breeding system.  The system includes a closed water loop, pumps, two 700ml fish tanks with LED lightings, an artificial lung and a nitrification bacteria filter.  Medaka and zebrafish were able to mate and spawn in this small breeding system, and young fish could grow to adult fish.  These results suggested the potential of small fish for multigenerational experiments in space.  Xenopus laevis breeding test with partially open air system will be also introduced.  They grew and completed metamorphosis in the small closed chamber.