By asking which genes were turned on during tardigrade anhydrobiosis, the scientists could identify sets of proteins, which appear to replace the water that tardigrade cells lose, thus helping to preserve the microscopic structures until water is available again.
Arakawa explained that all cells contain around 60–80 percent water when they are active, including human cells.
The key proteins that they identified are highly soluble. They dissolve in water that, due to surface tension, clings to and surrounds intracellular molecules within tardigrades. Like a microscopic protective coating, they prevent the cells from denaturing when the animal otherwise desiccates.
Arakawa added that tardigrades also possess additional genes that protect their DNA from damage. Because these small animals lack stress-sensing pathways, their cells do not usually die out when damaged. Instead, the identified proteins try to make repairs, and are often successful in doing so.
Due to these abilities, scientific consensus holds that tardigrades could be Earth’s last survivors. Such resilience is unexpected in a tiny creature that seems to exist in the slow lane.
“Tardigrades are slow walkers, and are not really aggressive animals,” Arakawa explained. “Therefore, they tend to lose competitions for food, or can become prey in a diversified ecosystem. But tardigrades fled to their own niche, where only tardigrades can survive, so paradoxically, tardigrades presumably acquired their extreme survival abilities due to their ecological incompetence.”
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Arakawa and his colleagues can envision a day when enzymes, vaccines, human organs, tissues, and cells could be preserved in a state of anhydrobiosis instead of by liquid-nitrogen-based freezing.
“Some people have suggested that tardigrades could somehow travel through space to seed other planets with Earth-derived life,” Blaxter said. “That obviously didn’t happen on Earth, as only some tardigrades are able to do anhydrobiosis, and tardigrades are derived from other, more ancient forms.”
While it is doubtful that tardigrades are somehow hurtling through space now, these amazing animals continue to captivate researchers. Blaxter and Arakawa, for example, have been studying them with awe and admiration for years.
Blaxter, one of the few tardigrade genomics experts in the world, reminisced that his scientific career was sewn when, as a child, he was gifted with an animal encyclopedia by his parents.
“I especially pored over the weird and wonderful animals that were so beyond what I had seen with my own eyes,” he recalled.
When, many years later, one of Blaxter's Ph.D. students suggested that he study tardigrades, a lightbulb went off.
“We haven’t looked back,” he said.