Cone snails don't exactly strike fear into the hearts of all who gaze upon them, but it turns out that they can induce some wicked low blood sugar in the fish they target. The slow-moving predators have long been known to use neurotoxins to ensnare their meals, but a new study in the Proceedings of the National Academy of Sciences suggests that they add special insulin to the mix, too.
In addition to the insulin that they use to regulate their own blood sugar, two species of cone snail were found to produce insulin quite similar to that used by fish. And when researchers looked for it in the snails' venom, the found it in high doses.
Weaponized insulin would certainly be a neat evolutionary trick: The hormone, which allows the absorption of sugar by cells, is essential to life. But too much insulin causes cells to over-absorb sugar from the bloodstream. In extreme cases, insulin overdoses can even cause death.
So, by exposing a target to high levels of insulin, you could send them into hypoglycemic shock. Their blood sugar would drop so low that they'd become lethargic, making them easier to capture.
It seems like cone snails have mastered this insulin subterfuge: When researchers injected zebrafish with a synthetic copy of the fish-like insulin they'd found in the snails, it caused a sudden plummet in their blood sugar.
This isn't to say that the snails' neurotoxins are useless. In fact, they've killed several unwitting human divers.
But this snail-induced sugar coma could be what makes fish so docile as the mollusks wrap their bugle-like mouth-parts around them:
Once inside, the fish are dosed with a toxic cocktail to make sure they won't perk up and squirm away mid-supper.
This is the first time insulin has been found as a component in animal venom, the researchers told The Verge, showing that even the chemicals that keep an animal alive can be used in the evolutionary fight against it.