Scorpion-Eating Mice Feel No Sting
Ashlee and Matthew Rowe
A southern grasshopper mouse eats the Arizona bark scorpions that it has just killed.
Here's one of four Tasmanian devils that have just moved into new homes at the San Diego Zoo. They're the only Tasmanian devils in a U.S. zoo, and though they're in quarantine right now, they will soon be marquee attractions in the zoo's Australian Outback exhibit. Fortunately, Tasmanian devils don't actually spin like tornadoes and whirl through everything in sight.
It's fall in the northern hemisphere, the time when many bird species take wing and head for warmer climes. Which bird takes the longest non-stop flight of any in the avian world? This one does: the Alpine swift. Researchers at the Swiss Ornithological Institute and the Bern University of Applied Sciences in Burgdorf, Switzerland, have observed from collected data that Alpine swifts take little, if any, time off during their migration from Switzerland to their winter homes in Western Africa and back again the following year.
Meet the star-nosed mole. Its face won't launch a thousand ships, or even a dozen row boats, but it's the world's fastest eater and that puts it in the record books -- ahead of more comely creatures. If that weren't enough, its nose looks like a flower, allowing it to poke out of the ground, as though it were a plant. And the "flower" on its nose has the highest density of nerve endings known in any mammalian skin.
Alejandro Arteaga / Tropical Herping
Speaking of prominent proboscises, Pinocchio anoles were thought to have been extinct for about 50 years, but they have recently been rediscovered in the cloud forests of northwest Ecuador. They may have rejoined the world, but be careful believing anything they say.
Ever feel like you're being watched? Two owl butterflies drink from orange wedges, during a visit of the butterfly conservatory at the American Natural History Museum in New York.
It might not have spooky owl eyes, but the Atlas moth, another guest of the butterfly conservatory, is the largest moth in the world. We're gonna need a bigger light bulb.
Single file, everyone. Elephants and calves lumber across the plain on Oct. 8, 2013 at Amboseli National Park, approximately 137 miles (220 kilometers) southeast of Nairobi. The caravan of giants has no idea there might be a census taker overhead: The Kenyan and Tanzanian governments have begun a joint aerial count of elephants and other large mammals in the shared ecosystem of the Amboseli-West Kilimanjaro and Natron-Magadi landscapes.
Mike Kemp/In Pictures/Corbis
There are winners and losers in life, and this week the winner's column included Noodle, an 11-month-old female cocker spaniel/poodle cross breed (or "cockapoo," if you really want to rob the dog of its dignity) that won the Westminster Dog of the Year competition, a yearly match among Parliamentarians' pets. Here, Noodle enjoys the thrill of victory with Member of Parliament, and proud Noodle owner, Alan Duncan.
Noah, a baby yellow-footed rock wallaby, and not owned by a Parliamentarian, sits on a rock in the Tierpark Zoo in Berlin, Germany, on Oct. 11, 2013. About eight months old, the cub spent several months in its mother's pouch and has now decided it's time to emerge and meet the public. Yellow-footed rock wallabies are an endangered species, and the Tierpark Zoo, along with some other facilities, maintains a special breeding program for them.
Then Chih Wey/Xinhua Press/Corbis
Wildlife Reserves Singapore has been on a roll in 2013, its breeding program having produced more than 400 animal babies between January and August. This female orangutan in the Singapore Zoo is a prime example of the program, as she cradles her two babies on Oct. 3, 2013. The baby at left may or may not be busy sending a text message to someone. Kids these days ...
The sting of the Arizona bark scorpion is so fierce that humans say the pain is like being hit by a hammer. But the tiny grasshopper mouse shakes off the sting like it's nothing.
Now, researchers have found for the mouse, the sting really is nothing. Instead of causing pain, the scorpion venom blocks it, a fact that could lead to the development of new pain-blocking drugs for people.
"The venom actually blocks the pain signal that the venom is trying to send" to the mouse, said study researcher Ashlee Rowe of Michigan State University. "We don't want to try to sound too cute or anything, but it is sort of like an evolutionary martial art, where the grasshopper mice are turning the tables. They're using their opponents' strength against them."
Southern grasshopper mice (Onychomys torridus) are carnivorous desert-dwellers. Among their favorite meals are the Arizona bark scorpions (Centruroides sculpturatus). The scorpions' sting would kill any other rodent the size of the grasshopper mouse, but the little rodent can absorb many stings in the course of attacking a scorpion. In studying this phenomenon, Rowe noticed not only did the mice survive, but they also seemed unconcerned. (See Video of a Mouse Attacking a Bark Scorpion)
"I was really intrigued by the fact that the mice, if they get stung, they just groom a little bit and then it's over," Rowe told LiveScience.
Clearly, the mice had evolved to handle the pain. To find out how, Rowe and her colleagues analyzed how the toxin acts on the nerve cells called nociceptors that pick up and relay pain to the mouse's brain.
Nerve cells communicate pain to the brain by translating stimuli into electric pulses. To do so, tiny channels in the cell membrane, called ion channels, open and close. One ubiquitous type of ion channel, the sodium/potassium channel, is present in cells throughout the body. This channel makes critical bodily functions, from breathing to muscle contractions, possible.
Typically, scorpion venom acts directly on sodium/potassium channels in nociceptors to create the sensation of pain. A specialized channel known as channel 1.7 is responsible for picking up the pain signal, whereas a channel called channel 1.8 carries it to the brain.
"They just turn (the nerve) on and send that signal to the brain," Rowe said.
Not so in the grasshopper mouse. In these rodents, the scorpion toxin binds to channel 1.8. (See Photos of the Amazing Grasshopper Mouse)
Cutting a wire
By binding to this transport channel, the toxin shuts it down, effectively blocking itself, Rowe and her colleagues report Friday (Oct. 25) in the journal Science.
"It's kind of like cutting a wire," Rowe said.
The finding explains why the mice seem to feel almost no pain when stung. Instead of acting as a painful stimulus, the toxin ends up acting like an analgesic.
Rowe thinks the grasshopper mice may be one of several animals that have evolved to withstand the scorpion's sting. She's currently investigating three possible creatures that might also feel no pain — though she prefers to keep the identities of those animals a secret until further testing. (Rowe won't be forcing scorpion showdowns in the name of this research; rather, she'll do genetic testing to look for signs of venom resistance.)
The ultimate goal of this work is to find new ways to ease pain in humans.
"One of the things we think is really important that's come out of this is to highlight the importance of sodium channel 1.8 and its ability to block pain signals," Rowe said. If scientists can figure out precisely how the toxin and the nerve cells interact, they may be able to produce compounds that mimic the venom's action. Such basic research also helps researchers understand how these crucial ion channels work
"These toxins do all kinds of interesting things to the channels," Rowe said. "They close them, they open them, they manipulate them in ways we can't imagine."
More From LiveScience:
In Photos: Top 10 Deadliest Animals
13 Oddest Medical Cases
The 10 Most Common Poisonous Plants
Copyright 2013 LiveScience, a TechMediaNetwork company. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.