Video: Young beetles pump their abs to breathe

To compensate for their large size, most big insects have developed a special way of breathing: They flex their abdomens like belly dancers to pump out carbon dioxide and to push oxygen through their tracheal tubes into the rest of their cells. But for a long time, scientists assumed this kind of active ventilation happened only in large or particularly active bugs. Now, researchers have discovered that the tiny pupae of the darkling beetle (Zophobas morio, above) exhibit the same type of abdominal flexing. But does it serve a role in breathing? To find out, the researchers used high-powered x-ray imaging to observe when the insects’ breathing tubes collapsed—a sure sign of active ventilation. They also measured rates of abdominal pumping and external gas exchange along with hemolymph (blood) pressure. As expected, abdominal pumping resulted in high blood pressure, tracheal collapse, and carbon dioxide release—that is, breathing. But this happened only 37% of the time the pupae were flexing their abs, the team reports this month in Biology Letters. The rest of the time, there was no tracheal collapse or gas exchange, leading researchers to believe that the pumping could serve other functions, from internal gas mixing to—the leading theory—blood circulation.