There are animals so rare on this planet that they could pass for aliens. Some are because of their appearance, others because of their body architecture, their habits or their metabolism. But one of them is for almost everything at once. The ratopín, or naked mole rat, is a separate case, a species (Heterocephalus glaber) unique of its kind (Heterocephalus), and a unique gender in its family (Heterocephalidae). It is the animal that nobody sees during a safari, and yet it is there, under the savannas of Kenya and Ethiopia; the presence of its underground tunnels is sometimes revealed in the form of small sand volcanoes that expel puffs of dust.
Those who see it, in zoos, or in photos and videos, often find it rather unappealing, like a half-grown, pink and hairless rat, with tiny eyes and prominent incisors that seem ready to peck. But its appearance is only the calling card of the rest of its rarities, to which a new one is now added. We review some of the eccentricities of the ratopín, starting with the last of its secrets, published this week in the magazine Science.
They switch to “plant mode” when there is no oxygen
The ratopines live in complex underground burrows, where they huddle together forming large colonies of up to 280 individuals. Clearly, under such conditions, oxygen is a scarce resource. These mammals are capable of surviving for hours in a very rarefied environment, and last up to 18 minutes in the total absence of oxygen. They just stop breathing; They go into a state of suspended animation and their heart rate slows to a quarter. But how do they do it?
A study led by the University of Illinois at Chicago (USA) and the Max Delbrück Center for Molecular Medicine in Berlin (Germany) reveals the solution. When the essential oxygen to burn glucose, the animals’ natural fuel, is lacking, ratopines simply stop consuming this sugar. Instead, they switch to another alternative energy source. “We were surprised to find high levels of two unusual sugars, fructose and especially sucrose, in the blood of oxygen-deprived ratopines,” says study co-lead author Jane Reznick.
In other mammals, certain organs such as the liver can metabolize fructose; but never the brain or the heart, whose cells die rapidly when there is no oxygen to consume glucose. In contrast, ratopin has the enzymes necessary throughout its body to use fructose as fuel. This sugar is found in vegetables, free or in the form of sucrose, better known as table sugar. This is why, according to the researchers, ratopines avoid dying by suffocation by behaving like plants.
Social like termites, and they eat feces
The ratopines and the Damaraland mole rats are the only mammals recognized by many scientists as eusocial, a term that describes life in fully hierarchical and caste-organized societies, in the style of ants or termites. Each colony of ratopines has a queen, the only fertile female, and several reproductive males. The members of the group cooperate in the upbringing of the little ones and divide up the tasks, such as defense, tunneling or searching for the roots and tubers that they use as food. However, the diet of ratopines also includes a dubious delicacy: their own feces. After weaning, this is the only sustenance for the young until they are able to digest the plant food.
They live 30 years and hardly suffer from cancer
Imagine a primate capable of living 800 years. Something similar is what the rattan does: live ten times longer than its cousin the mouse, of similar size. Its longevity of 30 years is an absolute record for a rodent. Among the causes of such a long life have been the slowing down of its metabolism that delays oxidation, or the existence of effective repair mechanisms for DNA damage. In addition, these animals reach such an advanced age with hardly any cancer. It used to be believed that ratopin was the only species free from this disease, until the first two cases were described in February 2016. Despite everything, it is still considered an animal extremely resistant to cancer, which could be due to a double safety mechanism that prevents uncontrolled proliferation of cells, and a compound in its tissues that blocks the migration of tumor cells.
They are “cold blooded”
Reptiles or amphibians use external sources such as the sun to regulate their body temperature. These animals were traditionally called “cold-blooded”, a name that is no longer in use today. On the contrary, the “warm-blooded”, like mammals, consume energy to warm themselves. The rattopin is the only known mammal that can be classified as a “thermoconformist”: instead of regulating its temperature by its own means, it adopts that of the environment around it. Although the thermal regulation of the rat is still a matter of study, its case is more closely related to what were classically understood as cold-blooded animals.
They do not feel pain or itching
A rodent scratching itself is a typical image, but not so much if it is a rat. One of the greatest rarities of these animals is that their skin lacks a neurotransmitter called substance P, involved in the nervous processing of pain signals and in the itching induced by histamine, the compound responsible for this sensation. The consequence is that ratopines scratch little, and are immune to skin pain caused by acids or irritants. It has been proposed that this trait is an adaptation to life in its tunnels, where high levels of CO2 they can cause a build-up of acid in their bodies.
They run in reverse
The ratopines show amazing adaptations to their underground existence. Their eyes are of little use to them, although they are not entirely useless. Their most distinctive feature is their powerful teeth, which they use for digging and which protrude through the lips so that they are sealed, to avoid swallowing the earth while drilling. The exceptional elasticity of their skin helps them crawl through tunnels. And if there is no room to turn, it does not matter: they can run in reverse at the same speed as forward.