This mole rat has evolved to feel no pain when the ants in its burrow bite Dewald Kleynhans, University of Pretoria

If you hate wasabi-flavoured snacks, you are not alone. All things in the animal kingdom, down to worms and flies, naturally avoid allyl isothiocyanate (AITC), the compound responsible for wasabi’s pungent taste. But now researchers have discovered the first species immune to the burning pain caused by exposure to AITC, raising the prospect of new pain relief in humans and boosting our knowledge of evolution.

The highveld mole rat (Cryptomys hottentotus pretoriae), which lives in the east of South Africa, proved completely insensitive to AITC when it was injected in its paw. The reason appears to be the similarity of AITC to the sting of the aggressive Natal droptail ant, which often live in the rats’ burrows.

An international team concludes that over millions of years, the rat has developed a particularly high expression for a gene that blocked the channel through which it would feel pain from AITC. That immunity gives the highvelds an advantage over other African mole rat species, allowing them to survive in areas others would not enter because of their sensitivity to the ant’s sting.


The blind watchmaker

“Evolution over millions of years works like a blind watchmaker, of how to fix the problem,” says Gary Lewin of the Max Delbrück Center for Molecular Medicine, Germany.

When his team used drugs to block the ‘short circuit’ protecting the rats from feeling the burn from AITC, they did react to the pain.

The understanding of the genetic mechanism for turning off pain perception could help people in future too. “This could help develop a therapy to shut down pain in humans,” says Lewin.

The rats are related to the ugly but exceptional naked mole-rat, which for years has been known to be immune to the pain caused by acid.

Journal reference: Science, DOI: 10.1126/science.aau0236