If you're ever attacked by an African naked mole-rat, don't bother with pepper spray. The bald little rodents can't feel the burn of capsaicin, the active ingredient in chilies, or the sting of acid, a new study reports.
The animals' insensitivity could be an adaptation to their cramped underground quarters, high in carbon dioxide gas that can turn to acid.
"They've got a fundamentally different mechanism in the way they sense acid from all animals ever tested," says Thomas Park, a neuroscientist at the University of Illinois in Chicago.
The buck-toothed rodents live in large hierarchical societies, like bees and ants, with hundreds of the critters packed into a network of tunnels. Workers dig the burrows and find food for a hyperaggressive, fertile queen.
In other animals, sensitivity to pain involves a molecule called substance P. Park's team previously discovered that naked mole-rats don't have substance P. To test the effect of the missing chemical, Park