Some beetles can shed most of their muscle during the winter and rebuild it by spring without moving, ready for flight, researchers have found.
The Colorado potato beetle (Leptinotarsa decemlineata) can survive up to four months buried beneath the snow in Canada with temperatures dropping to -20掳C. During hibernation, it slows its metabolism by as much as 90 per cent to save energy, but how it does this was poorly understood.
To investigate, at Western University in London, Canada, and her colleagues mimicked seasonal light and temperature changes in the lab and used an oxygraph to measure the amount of oxygen consumed by the insects鈥� mitochondria 鈥� the parts of the cells that convert food into energy.
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To their surprise, the oxygraph鈥檚 readings were zero. Once the researchers ruled out a glitch with the instrument, they peered under the microscope and discovered there were no mitochondria to measure because the beetle had lost nearly all of them.
鈥淚t was just a really exciting discovery and a simple explanation for why their metabolism was so low. I was banking on it being a little bit more complex,鈥� says Lebenzon.
More surprising still, the beetles had entirely restored the mitochondria by the spring without eating or moving at all.
In humans, muscles can waste away, or atrophy, due to many causes, including inactivity, but the only way to rebuild them聽is through exercise. And while some break down their flight muscles to save energy for processes like reproduction, they permanently lose the ability to fly.
It is likely that the Colorado potato beetle can restore its flight muscles so quickly on demand as it breaks down only the mitochondria 鈥� the most energy-demanding parts of the muscle 鈥� while retaining the nuclei of muscle cells and most of the protein, says Lebenzon.
鈥淲e think that it would take a lot more energy to rebuild everything from the ground up,鈥� she says.
The beetles begin losing mitochondria weeks before hibernation, so the process is finished in time for winter. They start ramping up mitochondria production a few weeks after becoming dormant so that their muscular thorax is restored and they are ready to fly as soon as they emerge from the cold.
Other insects also lose their flight muscle when hibernating, so it is likely that they too use the same process, the researchers say.
PNAS
