Slow, but Scary, Killer Snails

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The killers in some classic slasher movies are notoriously slow. Jason Voorhees, Michael Myers, and Leatherface all shamble along at a pace that makes little old ladies look like Usain Bolt. It’s got to be frustrating for someone with murder on their mind to get outrun by their victims. But real-world slow-and-scaries, the predatory cone snails of the genus Conus, have evolved a frightening way to make up for their speed deficit: venomous, harpoon-like teeth that can stab prey and drag them to the snail.

The snails bury themselves in the sand and lie in wait or sneak up on their prey, using a specialized chemical-sensory organ to detect a meal. Once a victim is in range, the snail strikes. It points its long, flexible proboscis at its victim and launches a modified radular tooth—hollow, barbed and made of chitin—from it. The tooth is loaded with a cocktail of neurotoxins that reduce pain to pacify the prey and quickly paralyze it by blocking neurotransmitter receptors. The tooth is still attached to the radula structure, so once the prey is subdued, the snail draws both the tooth and its dinner right into its mouth. After the meal has been processed, the snail pukes up any leftover indigestible bits along with the used tooth, and readies another one to fire. You can see the a snail do the jab-and-grab and then swallow a fish whole in this National Geographic video.

The snail’s venom gland and the toxins it makes have fascinated scientists for more than a century. A researcher from Canada’s University of Victoria recently discovered that the venom glands of the species C. lividus come from a bit of “epithelial [tissue] remodeling” and are formed when a part of the esophagus pinches off as the snail transitions into adulthood. The researcher suggests that this tissue tweaking process allowed the snail to develop its weaponry and become carnivorous in a relatively short evolutionary timeframe.

Meanwhile, the speed and precision of the snails’ venom have led other researchers to look into it for medical use as a painkiller with few or no side effects. One painkiller derived from the snails’ arsenal has already been approved by the FDA. “Prialt” contains ziconotide, a synthetic equivalent of one of the snails’ many toxins, and is approved for use in treating chronic pain in patients with cancer and AIDS. Dozens of other cone snail toxins are still being investigated for use in pain relief and treating epilepsy, cardiovascular disease, Alzheimer’s, Parkinson’s, and other diseases and disorders.