Monday, November 30, 2015

This Animal Looks Like a Penis With Teeth... But It's Even Stranger Than That

This is a naked mole rat.

Yes, this is arguably the freakiest-looking animal on Earth.
Photo by Roman Klementschitz at Wikimedia Commons.

Naked mole rats are rodents that live in underground tunnels under East African savannas and grasslands. There's nothing all that strange about that... but how they have adapted to this lifestyle is unique... and, quite frankly, amazing.

For one thing, to cope with the low oxygen levels of the subterranean environment, naked mole rats have very low metabolisms and breathing rates. One of the biggest uses of metabolic engines in mammals is to produce our own body heat. These little guys have cut this big expenditure by being what may be the only ectothermic mammals on the planet. Ectotherms are animals like most fish, amphibians and reptiles that get most of their body heat from their environment, rather than making it themselves. Because naked mole rats want to exchange heat with their environment, they want to eliminate insulation... giving them their hairless and fatless bodies. Now when they bask in the sun at their tunnel entrances or huddle with their family they can take in all that warmth without anything getting in the way.

There are some benefits to having low metabolisms and not using much oxygen: Naked mole rats live for nearly 30 years (compared to 1-3 years in regular rats). Oxygen creates free radicals, highly reactive chemicals that cause damage to DNA, leading to a wide range of diseases. Naked mole rats don't just use less oxygen, but they have special proteins that are resistant to these damaging chemicals. They also produce a specialized super-sugar that has essentially eliminated cancer in this long-living species. What's more, these elderly rodents have managed to avoid dementia and osteoporosis, traits we hope to learn more about through ongoing research.

Naked mole rats have also developed some unique sensory traits. Living with your entire extended family in underground burrows means that you live in high levels of carbon dioxide and walls saturated in pee. These little guys don't even have any body hair to protect their pink skin from all that burning ammonia. Their solution: get rid of pain. These guys have no pain receptors for noxious chemicals like acids or capsaicin (the stuff that makes hot peppers hot). Furthermore, they are lacking a specific neurotransmitter, called substance P, that other mammals use to send many pain signals. Since naked mole rats have less need for sensation in their skin, they have developed brains that have repurposed about 30% of the sematosensory cortex (the part of the brain that interprets touch sensations) to their digging teeth!

Perhaps the strangest quality of all for these animals is their behavior. Naked mole rats are one of only two known mammals that are eusocial (the other being the Damaraland mole rat). Eusociality is a social organization common among bees, wasps, ants and termites, in which the colony has castes that include queens, workers and soldiers. Among naked mole rats, there is a single queen in the colony that mates with a few dominant males; workers that dig the tunnels, gather food, and care for the young; and soldiers that protect the colony from predators. Workers and soldiers are all reproductively sterile with undeveloped gonads and low hormone levels. However, if the queen dies, one of the non-reproducing females will go through puberty and take on her role as the new queen.

Now that you know that naked mole rats are so much more than just a "freaky thing", enjoy this naked mole rat rap (or maybe even a whole episode of Disney's Kim Possible, which features Rufus, the naked mole rat):


  1. Hi Miss Behaviour.
    Interesting article. Could you add some references to this article? Especially regarding their metabolic rate, thermoregulation and their neurological adaptations. Just interested to find out more about research that has been done.
    Thank you for a great blog!

    1. Much of this work was done by Jenny Jarvis at the University of Cape Town (she is now emeritus) and her colleagues, such as Nigel Bennett at the University of Pretoria. You may also want to check out work by Shelley Buffenstein at the University of Texas Health Science Center at San Antonio.

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