DEEP LOOK: a new ultra-HD (4K) short video series created by KQED San Francisco and presented by PBS Digital Studios. See the unseen at the very edge of our visible world. Get a new perspective on our place in the universe and meet extraordinary new friends. Explore big scientific mysteries by going incredibly small.

Commonly found in the Sonoran Desert, the Arizona bark scorpion (Centruroides sculpturatus) is the most dangerous scorpion in the continental United States. According to Keith Boesen, Director of the Arizona Poison & Drug Information Center, about 15,000 Americans report being stung by scorpions every year in the U.S. The worst stings, about 200 annually, are attributed to this one species. Its sting can cause sharp pain along with tingling, swelling, numbness, dizziness, shortness of breath, muscular convulsions, involuntary eye movements, coughing and vomiting. Children under two years old are especially vulnerable. Since 2000, three human deaths have been attributed to the Arizona bark scorpion in the United States, all within Arizona.

But there is one unlikely creature that appears unimpressed. While it may not look the part, the Southern grasshopper mouse (Onychomys torridus) is an extremely capable hunter. It fearlessly stalks and devours any beetles or grasshoppers that have the misfortune to cross its path. But this mouse has a particular taste for scorpions.

The scorpion venom contains neurotoxins that target sodium and potassium ion channels, proteins embedded within the surface of the nerve and muscle cells that play an important role in regulating the sensation of pain. Activating these channels sends signals down the nerves to the brain. That’s what causes the excruciating pain that human victims have described as the feeling like getting jabbed with a hot needle. Others compare the pain to an electric shock. But the grasshopper mouse has an entirely different reaction when stung.

Within the mouse, a special protein in one of the sodium ion channels binds to the scorpion’s neurotoxin. Once bound, the neurotoxin is unable to activate the sodium ion channel and send the pain signal. Instead it has the entirely opposite effect. It shuts down the channel, keeping it from sending any signals, which has a numbing effect for the mouse.[…]