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ScienceShot: How the Snail Picked Its Poison

It's frustrating to be a predatory snail: everybody can outrun you. To make that annoying meal hold still, the cone snail, a giant marine mollusk, evolved a mouthful of hollow harpoon teeth, which it loads with venom, lobs at prey to paralyze them, then retracts into its mouth. But the poison gland itself, which is anatomically unique in its spaghetti shape, has mystified scientists for over a century. Revisiting a strange observation by a 19th century French naturalist who believed that the venom glands developed from tissue stripped away from the esophagus, a researcher cut up baby snails and studied their throat anatomy. She found that a very small structural change in the esophagus, which would have been too small to disrupt an ancestral snail's herbivorous habits, becomes a venom gland after the snail becomes an adult. Reporting online today in the Proceedings of the Royal Society B today, the researcher says that this smooth transition may explain how these snails developed their complex arsenal and became carnivorous over a short evolutionary timeframe.

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