Growing vegetables and rice can no longer meet the scientific research needs of our astronauts, and Shenzhou 18 will raise fish in space for the first time.
The "golden partner" of zebrafish and goldfish algae was selected as the carrier of circulating aquatic ecosystems, mainly considering that zebrafish, as the third largest model animal in the world after mice, has a genetic homology of up to 87% with humans, and is highly similar to the functional mechanisms of mammals, making it an ideal vertebrate research sample.
We know that astronauts have planted rice, wheat, lettuce, dwarf tomatoes, Nansuke and other crops in space, realizing the dream of growing vegetables in orbit. But if you want to eat meat in space, or let humans reproduce in space, you need to conduct deeper research and experiments. This is also an integral part of our dream of "farming and fishing space".
Therefore, in the Wentian test module of the Chinese space station, there are many experimental projects of life science and biotechnology research, such as space growth experiments of animals and plants such as zebrafish, Arabidopsis, nematodes, and fruit flies.
Among them, the "space fish" raises zebrafish, because the fish is very similar to the human body's genes and physiological characteristics, and it is originally the "world's third largest model animal" and is often used as a sample for life science research.
In addition, zebrafish is ideal as a gene editing model, because of its large spawning capacity, low cost of obtaining a large number of embryos, transparent and easy labeling, and high screening efficiency.
In addition, zebrafish are relatively small, usually only 3-4 cm, with vigorous vitality and reproductive capacity up to 6-7 times a year, which has the demand for space research samples.
If you want to raise fish in space, you must have a self-sufficient environment, so it is particularly important to use "zebrafish + goldfish algae" to form a confined space to achieve a self-circulation system.
In this way, the oxygen produced by the photosynthesis of the algae can be used to breathe for the zebrafish, and the latter exhales carbon dioxide for the photosynthesis of the algae.
Therefore, the selection of zebrafish as a sample makes it easier for us to achieve the experimental goals at a lower cost and with a shorter cycle time.
In the Wentian experimental module, scientists have built a small and confined living ecosystem, and the main research object is zebrafish. This "aquarium" is closed and contains more than 1 liter of water, a few zebrafish, and some algae and microorganisms. In this ecosystem, fish are seen as "consumers", algae are "producers", and microbes are "decomposers". A complete water ecological circulation system has been built!
In fact, zebrafish have a long history in space, having visited the former Soviet Union's "Salyut V" space station in 1976, and in 2012, the Japan Space Agency also built an aquarium and sent it to the International Space Station. But they're only looking at fish per se, we're zooming in on human space health and vertebrate research.
Compared with mice, zebrafish have biological characteristics such as strong fecundity, rapid development, transparent embryos, in vitro fertilization, and in vitro development, which are more convenient for scientific research. However, before 2012, domestic research on zebrafish was very "niche", and only a few laboratories were carrying out relevant research.
But for the sake of life science research, scientists have set out to create their own "zebrafish national team". China's National Zebrafish Resource Center has also become recognized as one of the three major zebrafish resource banks in the world, accounting for 3% of the world's production.
In 2014, the mainland launched a space fish farming project. The space life science instrument development team of the Shanghai Institute of Technology and Physics, Chinese Academy of Sciences, undertook the research and development task. In order to realize the fish farming idea translated by the Wuhan Institute of Aquatic Sciences of the Chinese Academy of Sciences, scientists have come up with many methods, but it takes a lot of effort to get the small fish to accept the paste food, and the balance of oxygen supply between algae and fish makes the team even more anxious. Fortunately, in 8 years, because of the team's efforts, all problems have been solved.
In 2019, the space fish tank passed all the ground simulation experiments before the launch of the "Wentian Module", and cooperated seamlessly with the life ecology and biotechnology experiment cabinet system, so that today's Shenzhou 18 astronauts can carry out the task of "space fish farming".