A southern grasshopper mouse appr oaches and prepares to attack an Arizona bark scorpion. COURTESY OF MATTHEW AND ASHLEE ROWEGrasshopper mice of the southwestern US deserts (Onychomys torridus) have evolved to take advantage of a normally well-protected food source: the Arizona bark scorpion (Centruroides sculpturatus), which produces a toxic, pain-inducing venom that deters most predators. Thanks to a few amino acid changes in a pain-transmitting sodium channel, however, grasshopper mice can consume the venomous arthropods while feeling little or no pain from their sting, according to research published today (October 24) in Science.
“The grasshopper mouse has found a way, very cleverly, to disconnect the pain pathway,” said neuroscientist Thomas Park of the University of Illinois at Chicago, who was not involved in the research. Importantly, he added, this pain resistance is specific to the venom; the mice are still able to feel pain from other stimuli. “There are very useful aspects of pain, [so] you don’t want to be completely insensitive,” he said.
Evolutionary neurobiologist Ashlee Rowe began studying the grasshopper mouse and its bark scorpion prey as a graduate student at North Carolina State University. Early on, she noticed that the mice seemed to be resistant to the scorpion’s sting. “The venom seems to have absolutely no effect whatsoever,” said Rowe, who is now an assistant ...
