If you've ever ridden a roller coaster or endured an unpleasantly bumpy bus ride, you probably felt your guts move inside your body. In caterpillars, it happens all the time. In a study published online today in Current Biology, researchers report that the insect's gut—a long, thin tube that stretches from head to heel—moves independently of its skin every time it crawls. When a caterpillar inches forward, its two back legs and gut slide forward, causing the middle part of the gut to jump ahead roughly a full segment in the insect's body. After that, the skin arches forward to catch up, as seen in this video. Biologists aren't sure why caterpillars move like this, but they suspect it might have to do with their voracious appetites. A caterpillar's main function in life is to eat and grow. Detaching the gut from most of its legs helps keep movement from interfering with digestion.
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