Cone Snail Snare Fish by Putting Them in a Coma

Cone snails have turned to insulin as a weapon, a new study has found. When the underwater snail approaches its prey, it releases insulin, which causes blood sugar levels to plummet. Any nearby fish get an influx of insulin into their gills and their bloodstream, and they don’t have the energy to swim away to escape the cone snail.

Helen Safavi, the lead researcher on the study and research Assistant Professor of Biology at the University of Utah, said “The snail has a very large mouth, and it kind of catches the fish within the large mouth. It's very unique that an animal has come up with a way to target metabolism in prey."

Safavi and her research team found the insulin when they were screening venom from a variety of different cone snails. Many of these underwater snails release complex toxins that paralyze their prey, and in the past cone snail venom has been used to develop medication.

Some cone snails use small harpoons to spear their prey with neurotoxins, and these species don’t use insulin. Two species, Conus geographus and Conus tulipa use insulin in a “nirvana cabal” of toxins to disorientate and eat fish.

The researchers weren’t specifically looking for insulin, and they were surprised by the finding.   

Insulin is a hormone that helps regulate the blood sugar levels. Humans create insulin in the pancreas, but molluscs produce it in neuroendocrine cells, such as nerve cells. However, interestingly, these two cone snail species produce regular insulin as normal in their neuroendocrine cells, but the insulin they use to put prey into a coma is produced in their venom glands.

This is the first reported case of any animal using insulin in its venom, and is also the shortest insulin ever reported.

Frank Mari, a professor of chemistry and biochemistry at Florida Atlantic University said, "just as we thought there is everything to be known about insulin, somebody was able to see that you can isolate insulin to target prey.”