Friday, July 23, 2010

insect gut has mind of its own


Video - Visceral locomotory pistoning in crawling caterpillars.

The Scientist | In at least one species of caterpillar, the gut appears to slide freely back and forth, untethered to the surrounding tissue - an unusual mechanism that might help the insect digest food while it crawls up stems in search of its leafy meals.

"What they're describing here, as far as I know, has never been described in any other animal," said zoologist Michael LaBarbera, who studies invertebrate biomechanics at the University of Chicago and was not involved in the study, published this week in Current Biology.

For Manduca sexta caterpillars, crawling begins in the back of their approximately five centimeter long bodies. They lift up their rear legs, initiating a wave of contractions and elongations that eventually reaches the head. It seemed reasonable for first author of the paper, Michael Simon at Tufts University, to imagine that the internal organs would follow the same sort of motion.

But when he and his colleagues showered the caterpillars with high-energy X-rays from a particle accelerator - essentially getting their first look of their insides - they saw a frenetic and unexpected back and forth swooshing that did not look anything like what they could observe from the outside.

The swooshing revealed by the X-ray imaging came from air tubes, called trachea, that were attached to the intestine. "They looked like seaweed blowing in the ocean," Simon said. As soon as the caterpillars lifted their hind legs to begin crawling, the researchers could see the tracheas moving, as if the gut moved way before the rest of the body caught up.

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