As healthy as a (naked) rat

27 January 2023
4 min read
27 January 2023
4 min read

It's not pretty, in fact to some it might look like a sausage with big teeth. It's called Heterocephalus glaber, or naked heterocephalus or naked mole-rat.

These mole-rats are small, up to 15 centimetres long including the tail, and almost completely hairless, except for a few rare, shaggy hairs sprouting from a greyish, wrinkled skin and whiskers. Long rabbit-like incisors protrude from its huge mouth. Small ears looking like simple folds of skin protrude from its bald head. Naked mole-rats have tiny eyes that are hard to see and cannot see much. And for the most part they don't need to, because these rodents spend their entire life in the dark digging tunnels that start from a large central chamber and branch out underground for dozens of metres: a large underground city. Mole-rats live in colonies of up to a hundred individuals, all subjects of a queen.

The social organisation of naked mole-rats is only the first in a series of peculiar and surprising features. Naked mole-rats are the only mammals that, like bees or ants, live in colonies governed by a single female, a queen who is the only member that mates and reproduces with a few chosen males. All other mole-rats, females and males, just like worker ants, carry out the work necessary for the defence and maintenance of the colony: digging tunnels, caring for the pups, who are all brothers and sisters, cleaning and searching for food, i.e. roots, bulbs and tubers.

Another peculiarity lies in the fact that mole rats are the only ectothermic mammals, i.e. cold-blooded, like reptiles. They manage to live without warming themselves in the sunlight, as lizards do, because conditions underground in the desert are hot, very hot, up to 30°C, humid and with little oxygen. Naked mole-rats live and thrive in conditions that would be lethal for any other mammal. But how do they do it?

And here the most incredible aspect of naked mole-rats is revealed: they are animals with exceptional physiques.

First, they are long-lived. While any other 'normal' rat lives a couple of years at most, a mole rat reaches and sometimes exceeds 30 years of age. Certainly, life underground is tough but simplified: there are not many predators, nor are there cold and rain and adverse conditions. In nature, the first cause of death among mole-rats are snakes, the only predators able to enter the tunnels. In captivity, on the other hand, they never die from old age or disease but only from mutual aggression.

Nor do they die from old age or illness. It seems impossible but it is so. Research on captive-bred colonies has revealed that these animals do not suffer from some of the chronic diseases that affect other mammals, including humans, such as diabetes. They do not show the typical signs of physical decline brought about by advancing age, such as increasingly brittle bones or heart and lung problems. As for their skin, well that looks old even at birth.

Naked mole-rats do not feel physical pain, at least as we know it. To survive under extreme conditions, these animals have evolved a very high pain threshold; what would hurt us indescribably would leave a mole rat indifferent. The genetic mutation of certain pain receptors alleviates the suffering and pain of these rodents.

The superpowers of mole-rats do not end there. They seem practically immune to cancer. This is something that scientists are studying carefully: understanding how these animals manage to live to thirty years without ever developing a tumour could unlock secret biological mechanisms that are also important for human health. It is actually not true that a mole-rat's cells cannot become cancerous: many experiments have shown that healthy cells taken from different tissues of mole rats can become diseased if kept isolated in a test tube. But when they are in the mole-rat's body, this does not happen. This probably means that the immune system of the mole-rat quickly detects a cancer cell and prevents it from replicating.

Mole-rats live all together in cramped burrows where there is a lack of air, which is why they can withstand very low concentrations of oxygen that would kill any other mammal. Now researchers are trying to find out how they do it: important information that could be useful for treating all those diseases that affect people and prevent proper oxygenation of their bodies.

In short, they are rather ugly but resourceful animals.