Deadly Sea Snails Shoot Weaponized Insulin to Disable Fishy Prey

Although cone snails are slow-moving, they're definitely not defenseless. These creatures produce a vast array of fast-acting toxins that target the nervous systems of prey. Now, scientists have discovered that some cone snails actually add a weaponized form of insulin to the venomous cocktail that they use to disable fish.

Cone snails can be found in most tropical marine waters, especially around coral reefs. Each species makes a distinct cocktail of venom compounds that have evolved to target specific prey. Conus geographus is one of the most deadly and has killed dozens of people in accidental encounters; it traps fish by releasing a blend of immobilizing venoms into the water.

In order to better understand cone snails and their venom trap, researchers searched the gene sequences of all of the proteins expressed in the venom glad of Conus geographus. In the end, they found two sequences that looked surprisingly similar to that of the hormone insulin. In fact, the insulin genes were more highly expressed in the venom gland than genes for some of the established venom toxins.

"This is a unique type of insulin," said Baldomero M. Olivera, one of the researchers, in a news release. "It is shorter than any insulin that has been described in any animal."

The type of insulin found in venom glands seems to match the prey of a given cone snail. For example, fish insulin was present in the venoms of Conus geographus and Conus tulipa, which both practice the same fish-trapping method.

The snail insulin could actually be used as a useful tool to probe the systems the human body uses to control blood sugar and energy metabolism.

The findings are published in the journal Proceedings of the National Academy of Sciences.

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