Shenzhou-18 was successfully launched, and an "aquarium" with an internal capacity of 1.25 liters followed the crew into space.
This is the first time that space fish farming has been carried out in China, with zebrafish and goldfish algae as research objects, and a stable space self-circulating aquatic ecosystem has been established in orbit, achieving a breakthrough in the cultivation of vertebrates in space on the mainland.
Why Zebrafish? At the Jiuquan Satellite Launch Center, this reporter chatted with the relevant person in charge of the space application system.
Why zebrafish?
Zebrafish may seem inconspicuous, but they are very popular in the field of space science research and applications. In 1976, he followed the former Soviet Union's "Salyut V" space station into space.
In the experimental setup, zebrafish and goldfish algae form a micro-ecosystem.
This is because it has many advantages such as simple breeding, rapid development, short sexual maturity cycle, large egg production, and many transgenic and mutant strains.
As a vertebrate, zebrafish has a high genetic similarity of 87% with humans, and is a model organism, that is, a type of organism that can be used to study and reveal a certain biological phenomenon with universal laws in living organisms.
With the "flight" of Shenzhou 18, 4 zebrafish and 4 grams of goldfish algae also followed into space, and the mainland officially opened the first space fish farming.
"The direction of research varies from country to country, with a greater focus on micro-aquatic ecosystems made up of zebrafish and goldfish algae. Cang Huaixing, a researcher at the Center for Space Application Engineering and Technology of the Chinese Academy of Sciences and a consultant for space science experiments, said.
In the experimental setup, goldfish algae photosynthesizes through a lighting system to release oxygen, which is provided to the fish for respiration. The carbon dioxide exhaled by fish can be used for photosynthesis by goldfish algae, and the excreted feces can also be used as nutrients for algae, thus forming a binary ecosystem.
Space experiments are not only about fish and algae, but also about metabolites in the system, the pH of water, and so on. To put it simply, it is to study the balance between the various types of organisms in the ecosystem.
"Although it is possible to simulate a microgravity environment on the ground, it is still different from the actual situation. The impact of the space environment on the material and energy cycles of this small ecosystem is unknown and needs to be studied in depth. Cang Huaixing said.
Build a model system
As the designer of the uplink space experiment plan and the core sample unit, Cang Huaixing has been at the Jiuquan Satellite Launch Center during this time, following up the operation process throughout the process to ensure that the process is foolproof.
The binary ecosystem may seem simple, but it has already gone through a lot of exploration. Unlike ground-based fish farming, the situation is much more complicated in weightlessness. Something that should have been taken for granted has become a problem.
For example, feeding. Astronauts have a tight schedule of tasks on the space station, and it is difficult to find time to feed them regularly every day. The relevant team of the Shanghai Institute of Technology and Physics of the Chinese Academy of Sciences has carried out research on this, first of all, to solve the problem of fish food shape.
Traditional granular and sawdust fish food is difficult to put smoothly under weightless conditions. After some research, the team decided to make the fish food into a toothpaste shape, and carried out a lot of experiments to improve the composition of the fish food, so that the fish accepted this new food.
Unlike open feeding on the ground, space aquariums have an airtight design that requires an automated system to operate. The team tried automatic spring ejection and elevator-type rotary feeding, but they were not satisfied. After continuous exploration, a set of regular and quantitative intelligent feeding system was finally developed.
At the same time, the experimental device is equipped with a circulating filtration and purification system, which does not need to change the water in the space station, and is also equipped with an image sensor, which can take pictures and record videos to conduct behavioral research on fish.
The reporter learned that the eggs laid by zebrafish will be systematically collected and brought back to the ground by astronauts in the future for scientists to carry out the next step of research.
From the perspective of space food, China has realized "growing rice" and "growing vegetables", and what is the significance of "raising zebrafish"?
Cang Huaixing said that using this project as a starting point to build a model system, and then expanding the scope of experiments, will help build a new ecological environment and promote the construction of a space food production system.