World / Science & Health

Life lessons: Microscopic tardigrade 'water bears' can survive extremes, and may hold secrets for human health


Earth’s ultimate survivors can weather extreme heat, cold, radiation and even the vacuum of space. Now the U.S. military hopes these tiny critters called tardigrades can teach us about true toughness.

These animals are pipsqueaks, only about the size of a period. Under a microscope they look like some combination of chubby bear and single-eyed alien.

They are the closest life gets to indestructible. No water? No worries. Tardigrades survive. Antarctic cold, heat of 300 degrees Fahrenheit (150 Celsius), a lack of oxygen, even punishing radiation doesn’t stop these animals. They are so resilient in the face of so many dangers that scientists think their unique biology may hold clues to how we can make crops more resistant to drought, better preserve blood and medicines, and even make more effective sunscreen.

When the going gets tough for tardigrades, they curl up, dry out and wait. Then, when the environment gets better and they get water, they spring back to life. They can stay dormant for decades before reanimating.

In 2007, scientists put two species of tardigrades in containers, launched them into orbit and opened them up to the vacuum full of punishing radiation.

They lived and later multiplied.

There are as many as 1,200 species of tardigrades, and they live all over Earth. Not all have the ability to go dormant.

Tardigrades seem to be the first animals on Earth to have evolved legs. The legs look like a first draft: The rear two legs face backward, while the front six face forward.

If they are hurt when they are in an active phase and can’t go into survival mode, they die. But they don’t have a circulatory system or a skeleton, so that lets them curl up in a hypersurvival mode called “cryptobiosis.”

University of North Carolina biologist Thomas Boothby wanted to know how they manage to survive in “environments we think of as being impossible to live in.” So he isolated the genes that activate when tardigrades need to go into cryptobiosis.

Boothby engineered those genes into yeast and says their tolerance to drought increased 100-fold. He hopes the genes could also help crops better survive drought.

In December, the Defense Department’s long-term research arm gave Boothby a nearly $5 million grant to figure out what in tardigrade genes might help human health.

Boothby hopes to make bags of blood last longer than the current six weeks and allow them to be stored in a dried state so soldiers can take their own blood supply to battle or ambulances can carry more.

Tardigrade tricks may also help with preserving vaccines to help reduce the enormous cost and complexity of trying to keep vaccines cold. They could also potentially help preserve organs or damaged tissue.

Japanese scientists are studying whether tardigrade proteins could help them come up with a better sunscreen to protect against ultraviolet rays that cause skin cancer. A 2016 study showed that human cells augmented with a DNA protein unique to tardigrades reduced radiation damage in lab tests.

Tardigrades are so otherworldly that some theorize that they could easily exist on planets outside the solar system. Harvard astronomer Avi Loeb said “they could survive an impact by a rock and they could potentially be brought from another planet” to Earth.

Loeb and colleagues conclude that the water bears could survive most end-of-the-world scenarios — everything short of our sun blinking out. “It’s good to know that at least one creature on Earth has a chance of surviving no matter what,” Loeb said.