Diminutive and enchanting tardigrades, affectionately known as “water bears” and “moss piglets,” are famed for their almost inconceivable resilience. These tiny creatures can survive in extreme conditions such as the vacuum of space or the icy environments near absolute zero and have remarkable powers of revival.
A group of scientists recently found that tardigrades can trigger a molecular switch for a powerful dormant state, one of the key mechanisms of their exceptional toughness. This complex system enables the micro-animals to survive under harsh conditions. Researchers hope their findings could inspire future studies.
The study began with a spontaneous idea when a researcher placed a tardigrade into a specialized device that detects free radicals. Free radicals are unstable molecules with unpaired electrons that arise during normal metabolic processes and environmental stress from pollutants such as smoke. They stabilize themselves by stealing electrons in a process called “redox reactions,” which can damage cells and compounds.
However, in moderation, free radicals can act as important signaling molecules, influencing cell behavior. Researchers observed in several experiments that when tardigrades are subjected to stressful environments with high concentrations of salt, sugar, and hydrogen peroxide, they enter a protective dormant state called “tun.” The results indicate that free radicals seem to induce the animals to curl up into this state of dormancy, although the exact mechanisms remain to be explored further.
Researchers are exploring the interactions between free radicals and cell signaling, particularly the role of cysteine, in order to understand how these interactions influence the tardigrades’ powerful survival strategies.
Researchers introduced specific molecules in their study of tardigrades, which can inhibit the oxidation of cysteine. Under stressful conditions, these molecules can prevent the reaction between free radicals and cysteine, and the results suggest that tardigrades are unable to enter a dormant state. This finding reveals that the oxidation of cysteine may be a key mechanism for tardigrades entering dormancy.
The research findings were affirmed by Kazuharu Arakawa, a biologist at Keio University in Japan. He noted that these new discoveries align with past studies in desiccation-tolerant midges, suggesting that oxidation processes may also be a common trigger for the cryptobiotic state in water bears and other organisms.
However, there are still many mysteries regarding the knowledge of tardigrades. Comparative animal physiologist Hans Ramløv from Roskilde University in Denmark mentioned that tardigrades suspend their metabolism during dormancy, which cannot be explained solely by cysteine oxidation. Ramløv stated that much more research is needed to fully understand this dormancy mechanism.
Researchers Colin and Hicks also believe that extensive research is still needed to unravel the role of free radicals inside tardigrades. They also emphasized that water bears have various survival strategies to cope with environmental stress and detailed exploration of these strategies is planned for future research.
Additionally, the research team plans to study a variety of different tardigrades to investigate the application of cysteine oxidation across the biological world. They foresee this mechanism may be widespread among various animals. In the long term, Hicks hopes this work could provide in-depth insights into aging and space travel research, especially concerning the issue of free radical damage to key cellular components like DNA and proteins.
