New research uncovered how a beetle species shoots boiling chemicals at predators without harming themselves.
When threatened bombardier beetles can aim and directly shoot a boiling substance from a chemical reaction chamber in their abdomen, the University of Arizona reported. The reaction is so intense that it even creates "gun smoke."
"Understanding how these beetles produce - and survive - repetitive explosions could provide new design principles for technologies such as blast mitigation and propulsion," said the lead authors of the study. The study was led by doctoral student Eric Arndt and Christine Ortiz in the Department of Materials Science and Engineering at Massachusetts Institute of Technology in Cambridge.
The researchers used enzymes to clean the digestive chamber where the "ammunition" originates, and looked at it with optical microscopy. They noticed some regions of the chamber wall were thicker than others, and the area near the mixing valve was particularly thin and weak. The researchers hypothesized this cuticle would be displaced by the force of the reaction in a way that would influence the valve and shut down the flow of reactants.To investigate this idea, the researchers looked at the anatomy of Brachinus elongatulus beetles using ultrafast X-ray imaging.
"We could manipulate the beetles remotely using robots from a radiation-free control room, while the X-rays penetrated the beetle abdomen, allowing us to visualize the discharges inside," said Wendy Moore, of the University of Arizona. "...For each experiment we had to cool the beetle down, carefully set it up in the observation chamber such that the X-ray beam was aimed precisely at the defensive glands, seal the doors, walk over to mission control, flip the switch to allow the X-ray beam to enter the room, and use robotic manipulators to remotely touch the beetle's leg so it would blast. In some cases, just turning the radiation on caused them to blast."
The findings showed the beetles regulate ultrafast micro-pulses involved in the process in a passive way, rather than through muscle contractions. As the chemicals pass through the valve to the reactions chamber it explosively releases oxygen gas, water vapor and heat from the exit pore. Each of these explosions causes the elastic regions to expand and cut off the flow of reactants.
"It turns out the expansion membrane of the reaction chamber acts as a passive closure mechanism, which is something that had not been described or even predicted before this study," Moore said. "We also discovered that the chamber's anatomy varies between female and male beetles."
The findings were published in a recent edition of the journal Science.
WATCH;
