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A geographic cone snail inches along an Australian reef.

Photograph by Design Pics Inc.

Toxic Snail Puts Fish in a Sugar Coma, Then Eats Them

A slow-moving ocean snail snags fish by drugging them with insulin.

What happens if you need to catch your own dinner, but you're just not fast enough? If you're a slow-moving cone snail with a yen for sushi, you drug a bunch of fish.

The tropical sluggard kills by overdosing fish with a toxic cloud containing insulin, researchers report this week in the Proceedings of the National Academy of Sciences. Plummeting blood sugar levels throw the victims into a stupor.

Cone snails are notorious for stinging scuba divers tempted to pick up their beautiful shells. But the geographic cone snail (Conus geographus)—the most venomous cone snail of all, with several human deaths under its belt—takes its practice of poisoning to a whole new level.

"It looks like the fish is completely narced," says Christopher Meyer, a cone snail specialist at the Smithsonian's National Museum of Natural History, who wasn't involved in the study.

Once the fish are in a sugar coma, the cone snail reaches out with what's called a false mouth—it looks like it's throwing a cape over its prey—and drags a stupefied animal into its mouth. The snail then stings the fish with another set of toxins, just to make sure its victim is completely paralyzed.

Other compounds in cone snail venom produce similar results, says Helen Safavi-Hemami, who studies the toxins at the University of Utah in Salt Lake City. Victims become dazed and confused, leading researchers to call this group of toxins, including the insulin, the nirvana cabal.

But no other animal that researchers know of—except perhaps people—uses insulin to kill like this, lead study author Safavi-Hemami says. A sensational case in the early 1980s involved a husband accused of trying to kill his very rich wife using insulin injections.

"How brilliant is this," says Meyer, who has observed a close cousin of the geographic cone snail—named Conus tulipa—hunting and killing fish in the same way in Guam. The fish almost look like they're passed out drunk, he says, and now we know why.

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