Fish-hunting cone snails release insulin that can work as a weapon, sending nearby prey’s blood sugar plummeting and making the groggy fish easy for a less-than-speedy snail to catch.
This is the first insulin discovered in the complex venom brews that cone snails produce, says biochemist Helena Safavi-Hemami of the University of Utah in Salt Lake City. She and colleagues found the insulin during a standard screen of venom genes from two cone snail species (Conus geographusand C. tulipa). Instead of being a version of the compound that regulates mollusk metabolism, it seemed to be a version more likely to affect fish, they report January 20 in the Proceedings of the National Academy of Sciences.
They tested the hypothesis by releasing the cone snail’s fishy insulin into water where zebrafish larvae swam, causing them to become lethargic. Injecting that same insulin in adult fish caused their blood sugar levels to drop. The snails probably secrete the insulin as part of a preliminary barrage of venom components, called the nirvana cabal, that quiets fish enough for the snail to pull them into its elongated funnel-shaped mouth and inject more venom.