In the Earth’s ocean, is there a “little star” exploring space?

Zebrafish have become a new favorite in life science research due to their convenient breeding, short breeding cycle, large egg production, in vitro fertilization, in vitro development, and transparent embryos. There are more than 1,500 zebrafish laboratories worldwide. Zebrafish are also ornamental fish, popular for their beautiful colors, easy breeding, and low risk of disease.

Zebrafish are native to freshwater rivers, streams, and rice paddies in South Asia. These places have gentle water flow and relatively stable water temperature, providing suitable living conditions for zebrafish. Zebrafish live in groups, and members of the group determine social hierarchy by biting and chasing each other. Zebrafish with higher ranks enjoy privileges in choosing spawning locations and obtaining food resources.

Zebrafish have strong reproductive capacity and a short reproductive cycle. Female zebrafish can lay dozens to hundreds of eggs each time. They usually lay their eggs in aquatic plants or cracks on the bottom of the water. The eggs hatch quickly and can hatch into fry within a few days at a suitable water temperature. After the fry are born, they grow at a considerable rate.

The embryonic development process of zebrafish is transparent, which allows scientists to directly observe the development of internal organs of the embryo, such as the formation of the heart and neural tube, without destroying the embryo. This provides an ideal model for studying gene regulation, cell differentiation and other processes in human embryonic development. Many human diseases have similar manifestations in zebrafish. For example, zebrafish can be induced to produce symptoms similar to human cardiovascular diseases and neurological diseases (such as Alzheimer's disease and Parkinson's disease). By studying these disease models of zebrafish, the pathogenesis of the disease can be explored more quickly and possible therapeutic drugs can be screened.

"Zebrafish is a small model animal, with an adult body length of 3-4cm and a juvenile body length of only 1-2mm, occupying a very small volume in the precious space station." Professor Zhao Qingshun of the Institute of Model Animals of Nanjing University introduced that zebrafish, as a representative of lower vertebrates, has 87% homology with human genes, is easy to obtain and easy to raise, and is a commonly used experimental material in physiology, ecology, toxicology, genetics, developmental biology, molecular biology and other research. It is now increasingly widely used in disease model creation, gene function evaluation, drug screening, toxicity testing, and environmental health risk assessment. In addition, zebrafish also has relatively complete genetic manipulation techniques, such as gene knockout and gene editing, and is the third largest experimental animal after mammals such as rats and mice.

On November 4, 2024, the seventh batch of space science experiment samples from the Chinese space station returned successfully with the Shenzhou 18 spacecraft. Among them, the returned zebrafish culture water base and eggs laid in space and other experimental materials became the "stars".

Raising fish in space is obviously not for aquaculture, but to enable humans to stay in space for longer periods of time and establish a more complete ecological circulation system and life support system through this research. At that time, the little zebrafish flying into space will play an indispensable role.

References:

[1]. Yuan Yuqing. Zebrafish flying into space[J]. Animal Spirits.

[2]. Xu Qimin. Equipped with zebrafish and goldfish, the “space fish tank” was built in Shanghai[J]. Wenhui Daily.

[3]. Zhang Xuan. How zebrafish taken into space can help medical research[J]. Xinhua Daily.

[4]. Liu Yao. What is the secret of “raising fish in space”? [J]. People’s Daily.