The painful, potentially deadly stings of bark scorpions are nothing more than a slight nuisance to grasshopper mice, which voraciously kill and consume their prey with ease. When stung, the mice briefly lick their paws and move in again for the kill.
The grasshopper mice are essentially numb to the pain, scientists have found, because the scorpion toxin acts as an analgesic rather than a pain stimulant.
The scientists published their research this week in Science.
Ashlee Rowe, lead author of the paper, previously discovered that grasshopper mice, which are native to the southwestern United States, are generally resistant to the bark scorpion toxin, which can kill other animals.
It is still unknown why the toxin is not lethal to the mice.
"This venom kills other mammals of similar size," said Rowe, Michigan State University assistant professor of neuroscience and zoology. "The grasshopper mouse has developed the evolutionary equivalent of martial arts to use the scorpions' greatest strength against them."
Rowe, who conducted the research while at The University of Texas at Austin, and her colleagues ventured into the desert and collected scorpions and mice for their experiments.
To test whether the grasshopper mice felt pain from the toxin, the scientists injected small amounts of scorpion venom or nontoxic saline solution in the mice's paws. Surprisingly, the mice licked their paws (a typical toxin response) much less when injected with the scorpion toxin than when injected with a nontoxic saline solution.
"This seemed completely ridiculous," said Harold Zakon, professor of neuroscience at The University of Texas at Austin. "One would think that the venom would at least cause a little more pain than the saline solution. This would mean that perhaps the toxin plays a role as an analgesic. This seemed very far out, but we wanted to test it anyway."
Rowe and Zakon discov
|Contact: Ashlee Rowe|
University of Texas at Austin