Snails, the slow-moving gastropods we often glance over, but some are anything but lethargic. Cone snails, for example, lie patiently in the shallows, waiting for an unsuspecting prey item to cross its path and that's when it springs into action. In the blink of an eye, the marine gastropod harpoons the now-meal with a hypodermic-like extension of its mantel, simultaneously injecting a lethal amount of immobilizing venom. The prey, within an equally quick time, is immobilized and later consumed by the predatory snail. But just what that quick-acting chemical concoction is made up of has baffled marine biologist for decades. Researchers at the University of Utah recently discovered that one compound of the snail's paralyzing toxin wasn't really poisonous at all: it was insulin.
"This is a unique type of insulin. It is shorter than any insulin that has been described in any animal. We found it in the venom in large amounts," lead researcher of the study and professor at the University of Utah, Baldomero Olivera says.
What's also interesting about the toxicology of cone snail venom is its inherent adaptability to each species' endemic environment. For example, cone snails that prey on primarily small damsel fish have been documented to produce a different chemical composition than those of snails that are observed feeding on other types of marine prey, such as ocean-going worms and other invertebrates.
Generally speaking, venoms that are able to immobilize the injected fauna rapidly usually contain neurotoxic properties; "neurotoxins" are protein-specific venoms that target specific neurological functions such as rhythmic cardiac and respiratory functions.
"We already knew that these animals make hundreds of neurotoxins in their venom and compounds that cause tissue degradation and affect cardiovascular function," said fellow researcher at the University of Utah and co-author of the study, Helena Safavi. "Now we can add yet another mechanism to this list: the disruption of the prey's energy metabolism."
But what's interesting about the cone snails' insulin-laden venom is that, when injected into the prey, it makes the animal go into hypoglycemic shock. This, ultimately, drastically drops the prey item's insulin levels, impairing all cognitive and motile functions. And it's then, when the prey is at its most vulnerable, will the mollusk begin to consume the its prey-whole.
Cone snails occupy most of the world's warm coastal waters.
