AP Biology class blog for discussing current research in Biology

Beauty is Pain: and naked mole rats have neither

The naked mole rat is the ugly duckling of the rodent family. These small rodents can live up to 32 years, are virtually resistant to cancer, and have evolved to become immune to certain types of pain. Beneath its wrinkled, fleshy surface, the naked mole rat is the closest animal we have to an indestructible species.

A new study published October 11 in Cell Reports offers some reasons behind the rodent’s abilities. Minor evolutionary changes to the amino acids in their pain receptors make the naked mole rat highly insensitive to pain after birth.”We think evolution has selected for this tweak just subtly enough so that the pain signaling becomes non-functional, but not strong enough that it becomes a danger for the animal,” says lead author Gary R. Lewin, a professor at the Max-Delbruck Center for Molecular Medicine in Berlin, Germany.

Much of this is due to the environment and behaviors present in the mole rats life. Naked mole rats often live in large colonies, with up to 300 members. The constant digging of tunnels and over crowding should leave the mole rat in great discomfort, and highly prone to a condition called thermal hyperalgesia. Humans have the same condition, which we generally call heat sensitivity. Imagine entering a hot bathtub with a bad sun burn. When this happens, it’s because sensory receptors on your skin have been chemically “sensitized” by inflammation or high temperatures. Once those receptors are sensitized, even the smallest amount of heat will cause sensory nerves to send signals to the  brain that register this as painful. Naked mole rats lack this reaction.

Through a series of calculated and carefully designed experiments, Lewid and his team were able to pin point what differentiates naked mole rats from all other rodents- a change in their TrkA receptor. They discovered a switch of just one to three amino acid changes on one section of the naked mole rat TrkA receptor that make it less sensitive.

“Even though the naked mole rat’s version of the TrkA receptor is almost identical to that of a mouse or a rat, it has a very significant effect on the animal’s ability to feel pain,” says Lewin. The naked mole rat is built for efficiency. It’s an animal built to survive the toughest of conditions. Evolution has shut down everything that is not necessary in the naked mole rat, including nerve receptors.

In my opinion, the naked mole rat is pretty cool. It has learned to evolve in order to survive. Maybe this trait is why the this species of rodent in particular outlives all of its fellow rodents by over 25 years. My one question would be, “Is the ability to not feel pain always an advantage? Or can this sometimes lead an animal into dangerous situations?” Whatever the answer, the naked mole rat is an evolutionary success.



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  1. evansymes

    In the end of your first paragraph you wrote that mole rats are the closest things we have to an indestructible species. I agree that resistance to cancer definitely fits that profile but an inability to feel pain might actually make them more prone to destruction than a different species. Inability to feel pain might be beneficial in dealing with skin irritation like you wrote, but as the article hutcherozygous put forth above states, in many survival situations pain can be beneficial in that it prevents organisms from doing things that might harm them. Imagine if we as humans didn’t feel pain when we touched something really hot. We’d probably burn ourselves constantly and mess ourselves up. Also in terms of indestructible species, there is a type of jellyfish that is immortal! you can check it out here

  2. hutcherozygous

    Not being able to feel pain is definitely not always an advantage, but for the naked mole rat, it’s a good compromise. The mole rats still have an adequate nervous system, but with fewer pain nerve cells, which is useful in a harsh environment where the body needs to retain energy. Clifford Woolf, a neuroscientist at Boston Children’s Hospital and Harvard Medical School, said that “if an individual has mutations that reduce the capacity to feel pain, that’s extremely dangerous. It’s not a relief from pain; it’s a disaster.” This makes sense because the tradeoff between having normal sensations and not feeling any pain doesn’t benefit humans nearly as much as it does for the mole rats. More on this here:

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