Naked mole-rats are odd little mammals: their exposed skin is wrinkly, their blood is cold and they have a predilection for eating poop. A new study has uncovered another bizarre feature of these subterranean creatures. As James Gorman reports for The New York Times, researchers found that naked mole-rats can survive for up to 18 minutes in an environment devoid of oxygen by using a metabolic process normally associated with plants.
The study, published in the journal Science, sought to test how naked mole-rats have adapted to a unique way of life. Within their underground burrows, naked mole-rats live in unusually large colonies of up to 300 individuals, Thomas Park, professor of biological sciences at the University of Illinois at Chicago, explains in a Guardian video.
“The downside to living in very large numbers is that they use up all the oxygen and they overproduce carbon dioxide,” Park says. “Other subterranean mammals don’t live in very large numbers because they can’t handle the oxygen deprivation and the acidity associated with high carbon dioxides.”
During the first phase of the study, researchers placed naked mole-rats in a chamber with 5 percent oxygen—about a quarter of the levels present in the air that we breathe. While a mouse would only be able to survive a handful of minutes in this environment, the mole-rats were able to persist for five hours. They became a little sluggish, Rae Ellen Bichell reports for NPR, but were otherwise fine.
Next, researchers popped four mole-rats into a chamber with zero percent oxygen. While the critters passed out after about 30 seconds, their hearts kept beating for 18 minutes. When the mole-rats were removed from the chamber, they woke up and went about their business, seemingly no worse for wear. The three mole-rats who were exposed for 30 minutes, however, did die.
How did these resilient rats survive such adverse conditions? When researchers studied tissue samples taken from the rats during various points of the oxygen deprivation period, they observed a spike in fructose levels.
Most mammals, including humans, power their cells with glucose, which is broken down by the stomach and absorbed by the blood stream. This metabolic process requires oxygen—it’s “the whole point of breathing,” Gorman writes in the Times. Under normal conditions, naked mole-rats also run on glucose, but in extreme, low-oxygen environments, they appear to switch to a metabolic system fueled by fructose, which does not require oxygen. Prior to this study, writes Hannah Devlin of The Guardian, fructose-based biochemical processes had only been observed in plants.
Humans can store fructose in the liver and kidneys, according to NPR’s Bichell, but we don’t have the ability to create energy from it directly and we must convert it into glucose. Mole-rats, on the other hand, are able to convert to using fructose—a perfect adaptation for life in crowded underground burrows, where oxygen can be scarce.
Researchers hope to someday apply their findings to humans suffering from heart attacks or strokes, which can cause oxygen deprivation. But for now, the study paints a fuller picture of the naked mole-rat, which is as wonderful as it is weird.