Mouse vs. Scorpion- Who Do You Think Wins?

Ashlee Rowe, MSU.

Watch out, honey badgers- you’ve got a rival on the badass scene. The latest furry critter to compete for the hard-core crown is the adorable and unassuming grasshopper mouse. This rodent has the surprising ability to be able to withstand an otherwise deadly dose of scorpion venom, and actually use the venom to its advantage.

Grasshopper mice, which are native to southwestern United States, often feast on Arizona bark scorpions, which are more than capable of giving a nasty sting to predators. These scorpions possess a toxin that is capable of killing other similar sized mammals, but when the grasshopper mouse is stung during attack it merely licks its paws and carries on.

Om nom nom. Image credit: Jillian Cowles. 

It transpires that to the mice, the toxin actually behaves as a pain killer rather than a pain stimulant. “The grasshopper mouse has developed the evolutionary equivalent of martial arts to use the scorpions’ greatest strength against them,” said Ashlee Rowe, assistant professor of neuroscience and zoology at Michigan State University (MSU).

In order to find out more about these intriguing animals, Rowe and her team investigated pain responses by injecting either a control saline solution or small amounts of scorpion toxin into the paws of the mice. They actually found that the mice reacted to the saline solution to a greater extent than the toxin, which was measured by the amount they licked their paws after exposure.

Through further investigation, the scientists found that the mice possess a modified type of sodium channel present on nerve cell membranes that is involved in pain responses. In mammals, one type of sodium channel (Nav1.7) initiates a pain signal, and then another (Nav1.8) transmits pain signals to the brain.

Usually, when the toxin binds to these sodium channels they are triggered to open, permitting a flow of sodium ions across the cell membrane which in turn causes the neurons to fire and transmit a pain signal. The Nav1.8 channels of grasshopper mice, however, have amino acid variants that prevent their activation upon binding of the bark scorpion toxin. This means that rather than triggering a pain response, the toxin actually induces analgesia. The results were published last year in Science

This research could have important applications in medicine, as in the future it may be possible to target these particular sodium channels in order to develop painkillers that don’t produce unwanted side effects.

Check out this awesome action video released recently by MSU showing the grasshopper mouse taking on a scorpion. 

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