April 21, 2017

Naked mole-rats just keep getting weirder and weirder

Naked mole-rats are probably the weirdest and most wonderful animals in the world - and now it has been discovered they often behave more like plants than animals.

Why are naked mole-rats weird and wonderful? Take the name, for starters. All animals are naked (usually), but these actually look more naked than most. The next part of their name is two animals in one.

But the way they look is far from being the most remarkable thing about them. They live like termites, in colonies of 300 where a queen produces worker offspring. They don't get cancer and they are immune to a lot of pain, including that caused by chilli peppers.

Whereas mice live for a maximum of three years, the world's oldest mole-rat, "Old Man", died aged 32.

Surviving in zero oxygen

One other incredible thing about naked mole-rats is that they can survive for up to 18 minutes without oxygen; this is compared to the 20 seconds of a mouse.

A new report in the journal Science explains that when mole-rats have to go without oxygen, they use fructose as their energy source. That's the sugar used by plants, in contrast to glucose which is used by humans and almost all other mammals.

Together with colleagues, Thomas Park, a University of Illinois at Chicago neurobiologist and co-author of the new study, put a mole rat into an oxygen chamber containing only five percent oxygen, and admitted the team were "tense". Humans could not survive on 5 percent.

However, “They didn’t even go to sleep,” Park told The Washington Post.

Down at zero percent oxygen, the animals' heart rate fell from 200 beats per minute to about 50, to account for their situation, but they made a quick recovery once oxygen was reintroduced.

“They were able to survive up to 18 minutes without any apparent neurological damage,” said Jane Reznick, a study co-author and molecular biologist at the Max Delbrück Center for Molecular Medicine in Berlin.

Nobody knows where the fructose comes from

Scientist were previously aware of mole-rats' ability to cope with little oxygen and put the phenomenon down to an ultra-sticky type of hemoglobin that appears to make their cells super efficient.

Brand new to researchers, though, is the finding that fructose molecules flood the rodents' bodies when they are oxygen deprived.

The team analyzed the animals' vital organs, using a technique known as mass spectrometry, searching for hundreds of different metabolites.

"Boy, that was a big pile of data across the desk,” Park remembered. Nevertheless. “The fructose curves just jumped out.”

"We still don’t know where the fructose comes from,” Reznick said. It's possible mole-rats have a kind of fructose storage system, or, more strangely, have bodies that produce fructose by themselves.

Part human, part mole-rat 

Fructose and glucose are sugars used by different organisms, but those that use fructose for energy do so without needing oxygen as an important metabolic component.

Human cells have the genetic information needed to build the fructose pathway, however, they are generally inactive in our vitals organs. Fructose is instead processed in human livers, eventually resulting in fat cells.

Because our cells do technically have the information needed to use fructose in the way that plants and naked mole-rats do, Park wonders if: “In a time of crisis, could we turn ourselves a little bit into naked mole-rats?"

This would give us a better chance of surviving, and hopefully give a few more people the chance to answer "naked mole-rat" to the question "if you could be any animal, what would you be?"


Image credit: Smithsonian Institute