Nature & Environment
Grasshopper Mice Immune to Deadly Bark Scorpion Stings: Study [VIDEO]
Benita Matilda
First Posted: Oct 25, 2013 07:42 AM EDT
Bark scorpions, the most venomous scorpions, are known to have a reverse effect on grasshopper mice that feed with ease on the predatory arthropod. The scorpion stings act as pain killers for the grasshopper mice, according to a latest finding.
The study conducted by a group of researchers at the University of Texas, Austin, claims that grasshopper mice are immune to the painful and potentially deadly stings of bark scorpions. The grasshopper mice kill and feed on the prey with ease. Recently, scientists discovered the secret to this immunity. They found that the scorpion toxins play the role of an analgesic rather than a pain stimulant.
Prior to this study, the lead author of the paper, Ashlee Rowe, had discovered that grasshopper mice are resistant to the stings of the bark scorpions, which otherwise prove fatal for other animals. But Rowe was not able to find the reason why the toxin was not lethal for the mice.
"This venom kills other mammals of similar size," Rowe, Michigan State University assistant professor of neuroscience and zoology, said in a statement. "The grasshopper mouse has developed the evolutionary equivalent of martial arts to use the scorpions' greatest strength against them."
Mostly found in the southwest United Sates, the bark scorpions are nocturnal in nature. These specimens are incredibly resilient and are most adapted to the desert.
For this study, the researchers injected a small amount of the scorpion venom or nontoxic saline solution in the mice jaws. When the mice were injected with the scorpion toxin, they licked their paws (a typical toxin response) much less when compared to when injected with nontoxic saline solution.
"This seemed completely ridiculous," Harold Zakon, professor of neuroscience at the University of Texas at Austin said. "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."
The researchers then discovered that the toxin of the bark scorpion acted as a painkiller by binding to the sodium channels present in the pain neurons of the mouse. The toxin blocks the neurons from triggering a pain signal to the brain.
There are different sodium channels in the pain neurons namely 1.7 and 1.8. They noticed that when the toxins bind to 1.7 channels the channels open up and sodium flows in and triggers the pain neurons. On sequencing the genes for both the sodium channels, they noticed that the 1.8 channel in grasshopper mice contained amino acids, which are different from those present in the mammals that are not immune to the stings of the bark scorpions like rats, house mice and humans. They discovered that the scorpion toxin binds with one of the amino acids to block the activation of channel 1.8, thus reducing the pain response.
"Incredibly, there is one amino acid substitution that can totally alter the behavior of the toxin and block the channel," said Zakon. "The riddle hasn't been completely solved just yet, though. We know the region of the channel where this is taking place and the amino acids involved. But there's something else that's playing a role, and that's what I'm focusing on next."
The study published in the journal Science, is the first to discover that amino acid substitution in sodium channel 1.8 produces an analgesic effect.
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First Posted: Oct 25, 2013 07:42 AM EDT
Bark scorpions, the most venomous scorpions, are known to have a reverse effect on grasshopper mice that feed with ease on the predatory arthropod. The scorpion stings act as pain killers for the grasshopper mice, according to a latest finding.
The study conducted by a group of researchers at the University of Texas, Austin, claims that grasshopper mice are immune to the painful and potentially deadly stings of bark scorpions. The grasshopper mice kill and feed on the prey with ease. Recently, scientists discovered the secret to this immunity. They found that the scorpion toxins play the role of an analgesic rather than a pain stimulant.
Prior to this study, the lead author of the paper, Ashlee Rowe, had discovered that grasshopper mice are resistant to the stings of the bark scorpions, which otherwise prove fatal for other animals. But Rowe was not able to find the reason why the toxin was not lethal for the mice.
"This venom kills other mammals of similar size," Rowe, Michigan State University assistant professor of neuroscience and zoology, said in a statement. "The grasshopper mouse has developed the evolutionary equivalent of martial arts to use the scorpions' greatest strength against them."
Mostly found in the southwest United Sates, the bark scorpions are nocturnal in nature. These specimens are incredibly resilient and are most adapted to the desert.
For this study, the researchers injected a small amount of the scorpion venom or nontoxic saline solution in the mice jaws. When the mice were injected with the scorpion toxin, they licked their paws (a typical toxin response) much less when compared to when injected with nontoxic saline solution.
"This seemed completely ridiculous," Harold Zakon, professor of neuroscience at the University of Texas at Austin said. "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."
The researchers then discovered that the toxin of the bark scorpion acted as a painkiller by binding to the sodium channels present in the pain neurons of the mouse. The toxin blocks the neurons from triggering a pain signal to the brain.
There are different sodium channels in the pain neurons namely 1.7 and 1.8. They noticed that when the toxins bind to 1.7 channels the channels open up and sodium flows in and triggers the pain neurons. On sequencing the genes for both the sodium channels, they noticed that the 1.8 channel in grasshopper mice contained amino acids, which are different from those present in the mammals that are not immune to the stings of the bark scorpions like rats, house mice and humans. They discovered that the scorpion toxin binds with one of the amino acids to block the activation of channel 1.8, thus reducing the pain response.
"Incredibly, there is one amino acid substitution that can totally alter the behavior of the toxin and block the channel," said Zakon. "The riddle hasn't been completely solved just yet, though. We know the region of the channel where this is taking place and the amino acids involved. But there's something else that's playing a role, and that's what I'm focusing on next."
The study published in the journal Science, is the first to discover that amino acid substitution in sodium channel 1.8 produces an analgesic effect.
See Now: NASA's Juno Spacecraft's Rendezvous With Jupiter's Mammoth Cyclone