Molerat, Naked

[Lisbeth]

Death is temporary - the resurrection of the naked mole rat

24 April 2017


Imagine putting 100 mice in a shoebox, taping the box shut and burying it a metre underground. The result should be obvious – 100 dead mice. In fact, if any animal is deprived of oxygen for too long the result is fatal – any animal except one, that is.

When the naked mole-rat is completely deprived of oxygen, it stops breathing, its heart rate drops and it subsequently dies. However, its death is temporary and if within a certain time it is given oxygen again, it comes back to life.

While it is incredible that these tiny mammals from East Africa can survive chronic oxygen deprivation in the underground environments in which they live, the fact that they are able to bring themselves back to life is almost unbelievable.

*Prof Nigel Bennett and Dr Heike Lutermann, of the University of Pretoria's Department of Zoology and Entomology, are involved in an exciting study on this topic that has been featured in Science. Visiting researcher and another lead investigator in the study, Prof Thom Park of the University of Illinois in the USA, says: 'This was a challenge so big that it took three labs on three continents to solve it.' Prof Gary Lewin of the Max Delbrück Centre for Molecular Medicine at the University of Berlin, Germany, was the other lead investigator in the study.

While this discovery is going to necessitate rewriting the world's zoological textbooks, it also brings exciting prospects to the realm of human health. Understanding how one mammal is able to survive without oxygen could lead to human lives being saved in times of crisis, such as when someone is in a car accident or suffers a stroke or a heart attack.

While naked mole-rats are adapted to the high levels of carbon dioxide in their underground clay castles, this study observed the results when mole rats had no access to oxygen at all. During these periods, the naked mole-rat reduces its heart rate to the extent that it almost appears to have stopped. It keeps it pumping just enough to circulate blood. The scientists are not yet fully certain how these animals manage to reduce their heart rate to such an extent.

Oxygen deprivation is inevitable when more than 70 naked mole-rats live together underground in an area not much bigger than a rugby ball. Prof Park explains that generally oxygen does not diffuse very well through soil, particularly the clay soil in which naked mole-rats live. With so many individuals living in a confined space, oxygen is very quickly depleted and far too much carbon dioxide is produced. Describing the environment as hostile, Prof Bennett adds that the humidity in these conditions is nearly 100%. Roots of plants also produce carbon dioxide. Yet naked mole rats survive these hypoxic conditions without any long-term damage.

Through this international collaboration, the researchers discovered that when the naked mole-rat is deprived of oxygen, it uses internal pathways to survive that no other mammal uses. It alters its metabolic systems to function more like a plant than an animal, releasing fructose into the blood, which is then taken to the brain. Its brain contains cells that can utilise fructose, enabling cellular functions to continue. Aerobic energy production stops and the animal operates on anaerobic systems, relying on fructose for energy instead of glucose. Once oxygen is restored, they switch back to their usual pathways.

If scientists can understand the biochemistry of the naked mole-rat and unlock the mechanisms that switch the pathways during oxygen deprivation, increasing and activating the number of brain cells that are able to utilise fructose, they might be able to apply this knowledge to humans, improving our chance of survival in extreme situations.

The naked mole-rat is fascinating and defies most characteristics of a mammal. These hardy little animals have been recorded to live for over 30 years and studies suggest they are immune to cancer. They are also the only cold-blooded mammal. Their social structures give scientists much to grapple with, resembling social insects like bees rather than mammals.

These researchers are now planning to conduct a comparative study between social and solitary species to find out if these traits are common to all subterranean mole-rats.

In a world where trees are being chopped down to make space for development and with ever-increasing levels of carbon dioxide in the atmosphere, we may all soon be living in a hypoxic environment. Naked mole-rats might very well be the key to our survival.

Prof Bennett concludes: 'If this tiny animal is able to live for over 30 years with very little oxygen, imagine if we understood these pathways and applied them to humans…'

* Prof Nigel Bennett holds the Austin Roberts Chair of African Mammalogy and the SARChI Chair of Mammalian Behavioural Ecology and Physiology.

[okie]

Hmmm.... to survive being naked is tough enough , but without oxygen .... man , that is really taking it to extremes

[Lisbeth]

[Flutterby]

Very interesting.

[Alf]

Ugly little thing

[Lisbeth]

[Richprins]

This is utterly fascinating, Lis1

[leachy]

astounding stuff indeed......

[Lisbeth]

Underground talk: Sorry, who do you wish to squeak to? For the naked mole-rat, it won’t be any old rodent

By Tiara Walters• 4 February 2021

Nothing like scurrying around in the nude and living to tell the tail, South African and German scientists reveal.

Subsisting in budding empires beneath the soil, a rodent resembling a tiny, subterranean walrus has a lot to say to its mates – but only to dwellers in the hallowed chambers and passages of its own social colony. That’s because no one else would understand that colony, not even their nearest walrussy neighbours doing life in other colonies.

The naked mole-rat (Heterocephalus glaber) negotiates the world in the wrinkled confines of a pink skin stripped of fur. Protruding incisors adapted to tunnel through clay soil complete the look.

And, thriving underground, this East African rodent appears to have evolved, in some ways, the ultimate solutions to mammalian lockdown. It is resistant to certain types of pain and can survive nearly 20 minutes without oxygen. A naked mole-rat can be in its mid-30s before it forever surrenders its DNA to the tunnels that sustained it — a record-breaking achievement for the average rodent.

And now a study by scientists at Pretoria University (UP) and Berlin’s Max Delbrück Centre for Molecular Medicine (MDC) has found that these denizens of darkness chat to each other in surprising ways.


An older naked mole-rat checks up on its sibling. (Photo: Lorna Faulkes Photography)

Naked mole rats “use shared dialects to strengthen unity of their large colonies”, write the German-South African teams in a research article featuring on the cover of the latest issue of the journal Science.

“The social and communication skills of human beings and naked mole rats appear to have much more in common than anyone might have thought,” they note.

They are “very communicative creatures”, Professor Gary Lewin, head of the MDC’s Lewin Lab, pointed out in a statement.

“If you stand outside their home and listen, you can hear the little rodents quietly chirping, squeaking, twittering, or even grunting to one another. We wanted to find out whether these vocalisations have a social function for the animals, who live underground together in an ordered colony with a strict division of labour.”

The naked mole rat is one of only two “eusocial” mammal species – thus representing an extreme version of multigenerational colony living also displayed by termites, ants and bees.

Clustering in groups of up to 300 animals, most naked mole-rats – also known as “sand puppies” – spend their entire lives as the colony serfs.


Naked mole-rats greet each other. (Photo: Lorna Faulkes Photography)

Here, they protect the nest, run the creche and feed the queen, who, in turn, gets the unenviable task of birthing the serfs. In the interests of observing environmental constraints (such as territory and food), only a select few larger colony males will ever be allowed to mate with her.

These crinkly chatterboxes lived in laboratories in Berlin and UP during the study period, producing a dizzying discussion of about 36,200 chirps. Over two years, an algorithm analysed vocalisations belonging to nearly 170 individuals from seven colonies. And, after an initial training period, a specially designed computer program showed it could confidently tell which individuals made which chirps — sort of like tuning into Naked Mole Rat FM, and recognising the voices of individual commentators.

By scrutinising the chirps that naked mole rats use to greet one another, the researchers also determined that each colony probably has a distinct dialect, says MDC’s Dr Alison Barker, study lead author.

If chirps were made by an individual from the test subject’s own tribe, the test subject would start chatting to that individual without delay. If they were made by a resident from a foreign colony, however, the naked mole-rat snubbed it by chirping nothing – signs, if you will, of rodent cancel culture.

“That enabled us to infer that naked mole rats can recognise their own dialect and will selectively respond to that,” says Barker.

To determine how foreign naked mole rats would interact with new colonies, the researchers placed three orphaned pups with a queen who had given birth to a new litter. After six months, the foster pups assumed the dialect of their new home.

However, “dialect cohesiveness decreases with queen loss and remerges only with the ascendance of a new queen”, according to the research article.

The MDC and UP previously collaborated on international research that helped alter what science knew about death and pain management.


A colony of naked mole rats on the march. (Photo: Mathew A Harris)

In 2019, their investigations led to a discovery showing that African mole rats are insensitive to many types of uncomfortable stimuli, potentially holding a key to treating human pain. Their adaptations to an extreme environment – a lack of oxygen, a surplus of underground CO2, and near-100% humidity – could further aid such research, the team found.

Naked mole rats can also survive extreme oxygen deprivation in their “underground clay castles”, a 2017 study also involving MDC and UP demonstrated.

“The naked mole rat reduces its heart rate to the extent that it almost appears to have stopped. It keeps it pumping just enough to circulate blood,” they wrote. “Death is temporary and, if within a certain time [the naked mole rat] is given oxygen again, it comes back to life.”

Such knowledge could be applied to humans, “improving our chance of survival in extreme situations”.

Now, in their new experiments, the researchers hope to draw on observations from southern Africa’s eusocial answer to the naked mole rat, the Damaraland mole rat (Fukomys damarensis).

The team would like to isolate the mechanisms consistent with how such a communication culture evolves, ideally gaining deeper insight into what it takes to be the life and mole of the party. DM/OBP

The MDC and UP teams include Professor Gary Lewin, Dr Alison Barker, Lina Mograby, mathematician Grigorii Veviurko (now at Delft University of Technology), Professor Nigel Bennett and Dr Daniel Hart.