While the superheated chemical spray released by bombardier beetles only brings minor discomfort to humans, the defense mechanism’s ability to immediately kill attacking ants has always made it a matter of interest to scientists. Past studies have attempted to gain an understanding of the beetles’ near-instantaneous chemical explosion through external observation, but x-ray imaging is finally allowing researchers to study the mechanism internally and in real-time.
Around 1,400 known species of bombardier beetles exist in nearly every continent, and in a study published in the latest issue of Science, MIT doctoral candidate and lead author Eric Arndt focused his observations on the brachinines subfamily due to their ability to produce hotter and faster toxic sprays than their relatives. By using x-ray imaging, Arndt found that the brachinines’ defense mechanism is reminiscent of a chemical heat pack; the beetles have a pair of glands which have two compartments containing the ingredients for the spray, and the glands are separated by a valve which prevents those ingredients from mixing together. When a beetle feels threatened, it contracts the muscles surrounding the ingredient reservoir, which allows reactive solution into the enzyme chamber and triggers an exothermic reaction. Once the mixture is heated to around 100 degrees Celsius, toxic vapor is spewed out.
“This happens explosively,” wrote Arndt. “If you look at the video, it all happens in a single frame. If you do the math, it takes even less than that – about 10 milliseconds.”
Arndt hopes that his research team’s findings might have biometric implications, as a similar mechanism could be used to invent better fuel injectors for combustion engines or other similarly new and improved technologies.
“The elegance of this mechanism is remarkable,” concluded Arndt. “An interesting way of looking at this mechanism is that it uses chemical processes to do work. If you look at an automobile engine, there are hundreds of parts. This is a single part that uses chemical energy to do work without all those added parts.”
