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Naked mole rats, with their long incisors and beady eyes, are the subject of endless fascination. Not just for their beguiling looks, but for their apparent superpowers: they can deflect cancer and feel almost no pain.
Here’s everything you need to know about these creatures and their amazing evolutionary traits.
Although mole rats are in the rodent family, their closest relatives are guinea pigs, porcupines and chinchillas.
Naked mole rats, along with their close relative the Damaraland mole rat, are the only mammals in the world known to exhibit this behaviour. They live in subterranean colonies in East Africa where there is a queen and only two or three males responsible for reproduction. Like in an ant colony, the rest of the mole rats have specific roles to play to keep the group alive - from digging tunnels and finding food, to fending off predators like snakes. There can be up to 300 naked mole rats per colony, and the tunnels can stretch to 4km and be as large as six football fields.
The queen is always a fighter. Queens get to their position by fighting off other females and when a queen dies - or is considered a bit sickly or weak - a battle takes place to find her successor. They will sometimes use their long, protruding incisors to stab opponents, with fatal consequences. The winner will grow longer, the gaps in her vertebrate expanding so she can bear offspring, and she secretes pheromones in her urine which renders the competition infertile. To remain the queen, a female mole rat should be reproducing several times a year and literally trampling on her competition and subjects to show dominance.
Don’t feel bad for them. One look at these mammals and it’s clear that evolution has made sure they can cope with the conditions. The tiny eyes and almost completely sealed up ears are protected from the soil, and those unmistakable teeth grow outside the mole rat’s mouth to prevent it from eating soil as it uses them to dig new tunnels. They have no sweat glands, fur or fat, so they do not overheat in close quarters underground but instead adopt the ambient temperature or huddle close together to keep warm. They also have tiny lungs and use oxygen incredibly efficiently because of their ability to bind more oxygen in the blood. They have an incredibly low metabolic rate, conserving energy to such an extent they can live up to 32 years, the longest life span of any rodent.
It's well know the naked mole rat's ability to use oxygen is incredibly efficient. Academics from the University of Illinois at Chicago have found how the creature borrows a technique from the plant world to survive without taking on new oxygen supplies.
By changing from a oxygen-reliant glucose-based metabolic system to one that uses fructose, the mole rats can live while being deprived of oxygen. A research paper, published in Science, says the naked mole rat can go 18 minutes without taking-on oxygen.
Mole rats are remarkably ordered. They have burrows within colonies that are dedicated to nesting, eating and even farming - while digging tunnels they look for roots and pull them into burrows. If they find a large tuber, they eat it slowly, covering it up again so it continues to live. Back to hygiene - they also have a toilet burrow which every naked mole rat uses. Once it’s full, they close it off and dig a new one.
That is all.
Naked mole rats are generally irked when the queen pushes them around. Just enough to respect her authority. But biologists recently discovered that an acid burn was no biggie to a mole rat. The kindly research team used acid and capsaicin (the chemical that makes chills hot) to stimulate the rodent, and found the nerve signals went to the “touch region” rather than the pain region. “Their nerve fibres do not respond to acid at all,” the study concluded.
Another recent study in Cell Reports found that this is possible thanks to minute differences in a selection of amino acids in a receptor of the nervous system. The research team found that infant naked mole rats do have the normal amount of pain sensors - it is only in adulthood, by which time the rats have no doubt understood the limits that keep it safe and alive, that the number massively reduces by two-thirds. The team speculated that the loss of the pain sensors was part of the many ingenious ways the species has adapted to living in hot conditions in underground colonies; it could allow them to maintain vital energy and go towards explaining their long lifespans.
"They live in desert regions underground, and they have to do a lot of work to get their food. They have the lowest metabolic rate of any mammal. Evolution has shut down everything that is not absolutely necessary - including extra nerve receptors," said Gary R Lewin, a professor at the Max-Delbruck Center for Molecular Medicine in Berlin.
Up until this year, not one case of cancer among naked mole rats had ever been reported. Biologists from the University of Rochester in New York discovered that the matrix that supports tissues of a naked mole rat is full of a substance called hyaluronan which acts as a lubricant, but that also happens to prevent cancer from growing. The Rochester group found that if it prevented the mole rat tissue from generating the lubricant, it did in fact grow tumours. Scientists the world over proclaimed naked mole rats could be the key to wiping out cancer in humans.
Unfortunately, earlier this year cancer was discovered in two naked mole rats in a zoo. The group that made the discovery, from the University of Washington School of Medicine, still believes these two instances could help us learn even more about why naked mole rats tend not to suffer from cancer.
Quite a lot actually. The Google-backed Calico Labs, which is focusing on developing technology to slow ageing, has launched a new project studying naked mole rats and their mysterious ways. Calico's scientists are trying to sequence the naked mole rat genome in order to understand the animal's genetics and shed some light on how the animals appear to cheat the ageing process.
The lab's chief scientific officer, David Bostein, told MIT Technology Review the lab may have something profound to offer in the next 10 years at best, so we will have to wait and see what makes these interesting creatures age-defying.
This article was originally published by WIRED UK
