New research suggests some cone snails use insulin as a weapon to stun fish.
Snails are generally slow and unable to fight, but they appear to be making up for these weaknesses by developing the ability to produce toxins that attack the immune systems of their prey, the University of Utah reported. Some cone snails appear to have added a special form of insulin to their deadly cocktail.
"This is a unique type of insulin. It is shorter than any insulin that has been described in any animal," said senior author Baldomero M. Olivera, a distinguished professor of biology at the University of Utah. "We found it in the venom in large amounts."
This venom caused blood glucose levels to drop when injected into zebrafish and disrupted the swimming behavior of fish exposed through water contact. The team determined adding insulin to the mix of venom toxins allowed the snails to hit entire schools of fish with hypoglycemic shock. In order to release their mix of toxins the dangerous snails aim a "gun-like" mouth part at a target, which then engulfs the stunned fish.
To gain insight into this fascinating defense, a team of researchers looked at the gene sequences of all of the proteins expressed in the venom gland of Conus geographus. They found two of the sequences looked extremely similar to the hormone insulin, which regulates the immune system in humans and animals. A chemical analysis of the snails' venom confirmed it contained copious amounts of fish insulin.
The snail insulin could lead to new insights into controlling blood sugar and energy metabolism in the human body because this type of insulin contains 43 amino acid building blocks, which is fewer than any other known insulin.
The findings were published in a recent edition of the Proceedings of the National Academy of Sciences.
