According to SCMP, a group of zebrafish has spent 43 days living aboard China’s Tiangong space station, nearly three times longer than the previous record set by a similar experiment on the International Space Station (ISS).
The group of four zebrafish, along with a population of hornwort plants, was launched into orbit on the Shenzhou-18 spacecraft on April 25. This project aims to create a self-sustaining ecosystem to study the effects of microgravity and radiation on the species’ development and growth.
Zebrafish swimming inside a closed aquatic ecosystem at China’s Tiangong space station. (Photo: CCTV)
According to a report published in The Innovation, the zebrafish underwent their natural developmental stages—from growth and development to reproduction—within the 43-day period, setting a record for ecological experiments in space.
“This milestone not only marks a technological advancement in China’s space ecosystem but also provides valuable data and technical support for closed ecosystems in space missions,” the authors stated.
This achievement was made possible by the innovative Closed Aquatic Ecosystem System (CAES) on the Tiangong station, which includes a biologically regenerative life support system, a gas balance control system, and a microbiological processing system.
The intelligent and automated control systems within the closed ecosystem, such as the installed sensors, monitor water quality parameters like pH and conductivity to ensure a safe and sustainable aquatic living environment. The CAES is also equipped with a fluid pump that enhances metabolic exchanges between the fish and plant chambers.
Developing advanced life support systems is a necessary step for future space exploration. “This progress will certainly pave the way for humans to live and operate in space for extended periods, bringing the vision of long-term life and survival in space closer to reality,” the researchers concluded.
The survival time of the Chinese zebrafish group surpassed the previous record held by a German scientific team, which maintained the life of a swordtail fish in a balanced closed aquatic system during the STS-90 Neurolab mission aboard NASA’s Columbia shuttle in 1998—a pioneering project investigating the effects of spaceflight on the nervous system.
Zebrafish have many unique characteristics and share over 70% of their genes with humans. (Photo: Shutterstock)
Zebrafish are widely studied in life sciences and biomedicine due to their unique advantages, including sharing over 70% of their genes with humans. Their short reproductive and developmental cycles, along with their transparent eggs, also allow scientists to study internal characteristics as they grow.
As scientists further investigate the various effects of microgravity on the human body—from bones to the heart and brain—they have found zebrafish to be an ideal model organism for such experiments.
Space studies on zebrafish began in the 1970s when they were first launched into space during Russia’s Salyut 5 space station mission.
Other species of fish are also being studied in space. Japanese scientists have researched how reduced gravity affects tissue structure and bone remodeling by observing genetically modified medaka fish in space. Their findings, published in the journal Scientific Reports in 2015, showed that the mineral density of the medaka’s bones and teeth decreased after 56 days on the ISS.
Although the zebrafish on the Tiangong station were able to survive for a long time, they exhibited unusual orientation behavior in microgravity conditions, such as swimming upside down, spinning, and swimming in circles, according to the Shenzhou-18 crew.
On November 4, astronauts Ye Guangfu, Li Cong, and Li Guangsu returned to Earth after 192 days in orbit, bringing back dozens of scientific experiment samples, including microorganisms, alloy materials, and nanomaterials difficult to fabricate on Earth.
They also returned samples of water containing fish eggs and other specimens, along with video recordings of the zebrafish’s behavior in space.
According to Xinhua, scientists hope to use these material samples to learn more about the effects of the space environment on the growth, development, and behavior of vertebrates while supporting research on material cycles in closed space ecosystems.
