China aims to breed zebrafish on Tiangong space station

Science: According to updates on experiments, the zebrafish on China’s space station are performing well in orbit. These four zebrafish arrived at the Tiangong space station on April 26 aboard the Shenzhou 18 spacecraft, along with astronauts Ye Guangfu, Li Kang and Li Guangsu. The fish live in a tank that creates a small-sized self-sustaining ecosystem. According to state broadcaster China Central Television (CCTV), it uses a plant called hornwort, which performs photosynthesis to maintain the life of the fish. Scientists designed the experiment to study how the space environment affects their growth and overall system balance. Previously, the fish were seen doing strange things due to microgravity, such as unusual directional behavior and swimming upside down.

Scientists have expressed hope that the fish can lay eggs. If they do, Tiangong astronauts will be able to closely follow the development of any offspring, as zebrafish embryos are transparent and develop outside the uterus. If it happens, it wouldn’t be the first case of fish rearing in space, as medaka fish mated on a 1994 space shuttle mission. “In space, we conducted the country’s first in-orbit aquatic ecological research project – that is, rearing fish in space,” Li Guangsu said. “We observed the growth of zebrafish on the space station, which have been with us for several months. As the mission requires, we have to perform more than 90 experiments and tests, and they are all proceeding smoothly.”