The Cone Snail Is a Slow, but Highly Venomous, Predator

By: Jesslyn Shields  | 

cone snail
Cone snail shells are beautiful and highly prized by shell collectors worldwide, though they house a predatory species known mostly for its venomous ways. Tammy616/Getty Images

In the "Jurassic Park" sequel "The Lost World: Jurassic Park," the Lindstradt air gun is a weapon that shoots a dart containing "enhanced venom" from the cone snail (Conus purpurascens), which the movie purports to be the most powerful neurotoxin in the world. The gun is used to kill or paralyze dinosaurs, of course.

"In the movie, Conus purpurascens venom is described as the most powerful neurotoxin in the world that acts within 1/2000th of a second – faster than the velocity of nerve conduction," says Helena Safavi, a professor in the department of biomedical sciences at the University of Copenhagen, who studies cone snails and their venom. "None of this is true, but nevertheless very entertaining."

Cone snails are a group of around 1,000 species of venomous, predatory marine snails that live in shallow, tropical waters around the globe. Their cone-shaped shells are intricately patterned and brightly colored, prized by seashell collectors, and their venom is fascinating to biomedical researchers. Pretty high profile for a very slow, not particularly aggressive animal that spends its days toddling after worms, fish and other snails for dinner.

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But Why So Venomous?

Cone snails are very slow animals that have no means of mechanical prey capture – that is to say, they can't bite or grasp like a shark or a rattlesnake. Despite the lack of teeth and claws, all cone snails are inimitable predators, even though they cannot graze on algae like their non-venomous snail relatives.

"When a slow animal wants to hunt other creatures, it has to evolve potent venom to be successful. Particularly those cone snails that prey on fish have to have toxins that can potently immobilize the fish prey before it swims away," says Safavi.

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Unique Toxins

One of the most remarkable things about the 1,000-ish species of cone snail is that there is almost no overlap in the toxins that are made by each.

"This shows how fast these toxins evolve," says Safavi. "Even very closely related species have only around 5 to 10 percent overlap. With each species making several hundreds of toxins, one can estimate that there are around half a million different toxins present in cone snails."

Because their venoms are unique to specific species, some species deliver a very minor sting, and others can kill you.

"There are about 40 known fatalities by cone snails and nearly all — if not all — were caused by a single species, Conus geographus, commonly known as the geography cone," says Safavi. "Some of the toxins in this species can cause acute respiratory failure and potentially heart failure. It's also one of the species that can inject larger quantities of venom compared to most other cone snails. Compared to snakes and even scorpions and spiders, death from cone snail stings are extremely rare."

cone snail
The geography (or front-gilled) cone snail (Conus geographus) is responsible for most of the known human cone snail fatalities.
Reinhard Dirscherl/Getty Images

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Killing Techniques

Cone snails might not have fangs, but most have a venom-covered harpoon they use to incapacitate their prey. With a tube-like structure at the end of a venom bulb, and a modified tooth that can shoot out of the tube at 400 miles per hour (644 kilometers per hour), instantly incapacitating passing prey, it doesn't really matter if cone snails are slowpokes. All the snail has to do is reel its prey into its giant parachute-like mouth and spit the bones out a couple of hours later.

Other cone snails, like the geographer cone, creep up on sleeping fish and shoot out a cloud of chemicals – one of which is insulin — that numbs their prey and sends them into a sort of hypoglycemic coma before swallowing them whole.

Other cone snails will strike a fish but won't tether it with their harpoon. The fish will swim away, but will fall under the influence of the snail's venom pretty quickly. All the snail has to do is follow its prey and gobble it up when it reaches it.

These are just a few strategies, but according to Safavi, with so much diversity in cone snail venom, we have a lot to learn:

"We know very little about the various ways that cone snails use their venom in the wild," she says. "A colleague of mine recently showed that some cone snails use toxins that mimic mating pheromones to lure worms out of their burrows. It's really fascinating what these animals are capable of."

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