Animals, especially mammals, need oxygen to keep their bodies and brains humming along. But leave it to the African naked mole-rat to buck that trend. The rodents are bizarre in just about every way.
They’re hairless, ground-dwelling and cold-blooded despite being mammals. Now, scientists report in the journal Science that the animals are capable of surviving oxygen deprivation.
“They have evolved under such a different environment that it’s like studying an animal from another planet,” says Thomas Park, a neuroscientist at the University of Illinois at Chicago.
He and his colleagues knew that naked mole-rat bodies work differently than those of other mammals. For example, instead of generating their own heat, they regulate body temperature by moving to warmer or cooler tunnels, which lowers the amount of energy they need to survive.
They’re also known to have what Park calls “sticky hemoglobin,” which allows them to draw oxygen out of very thin air. And because they live underground in large social groups, they’re used to breathing air that’s low in oxygen and high in carbon dioxide.
Park and his colleagues wondered if they animals had another trick up their (nonexistent) sleeves for handling such extreme conditions. “We were thinking, ‘Gee, if you put all these things to bear on the problem of surviving in low oxygen, just how far can you go?’ ” Park says. “And the naked mole-rats surprised everybody, I think.”
To start out, he and his colleagues tested how well the mole-rats fared in a chamber with only 5 percent oxygen, which is about a quarter of the oxygen in the air we breathe, and can kill a mouse in less than 15 minutes. They watched closely, ready to pull the mole-rats out at the first sign of trouble.
“So we put them in the chamber and after five minutes, nothing. No problems,” Park says. An hour later, there were still no problems. Five hours later, the researchers were tired and hungry and ready to go home, but the mole-rats could’ve kept chugging along.
“Oh, I think so,” says Park. “They had more stamina than the researchers.”
The animals had slowed down a bit, he says, but were awake, walking around and even socializing.
“They looked completely fine,” he says.
Next, the researchers decided to see how the mole-rats dealt with zero percent oxygen.
“And that was a surprise, too,” he says.
Such conditions can kill a mouse in 45 seconds.
The four mole-rats involved in this leg of the study passed out after about 30 seconds, but their hearts kept beating and – a full 18 minutes later – the mole-rats woke up and resumed life as usual when they were re-exposed to normal air. (The three mole-rats that were exposed for 30 minutes, however, died.)