Cone Snail: A Slow but Highly Venomous Predator
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.
As we'll learn, there are some differences between the facts and the fiction surrounding these venomous creatures and the toxin they produce. So sit back and prepare to learn about the real-life cone snail, the truth of the cone snail sting and other details.
Movie Fiction vs. Fact
"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 mostly 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.
That's a pretty high profile for a very slow, not particularly aggressive animal that spends its days toddling after worms, fish and other snails for dinner.
Cone Snails: Pretty, With a Bite
Cone snails live all over the world, with most specimens found in subtropical and tropical waters. Their exquisitely patterned and colored shells are part of their appeal, but also part of what makes them dangerous: A person who is trying to collect cone shells might inadvertently disturb the snail, which is a good way to get stung.
Cone snails can be found in the intertidal zone of warmer oceans and seas, as well as deeper, in areas such as coral reefs. Whether you're wading through the shallows or going scuba diving in the warm, clear tropical ocean, be wary of these aquatic creatures.
Why Are Cone Snails So Venomous?
Cone snails are very slow animals that have no means of mechanical prey capture; they can't bite or grasp like a shark or a rattlesnake. While most venomous creatures can rely upon speed and fangs as well as a toxic venom, cone snails make efficient predators without those tools.
Some sea snails, like most land snails, are herbivores, and don't have to worry about capturing live prey. Cone snails, being fish and worm eaters, need a way to hunt their prey.
"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.
Unique Toxins
One of the most remarkable things about the 1,000-ish cone snail species 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 cone snail species deliver a very minor sting, while other species of cone snail can kill you. Safavi says:
"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. 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."
Hazards and Hopes From the Cone Snail Venom
Medical researchers have long been interested in the neurotoxic peptides found in the venom of the genus Conus, to which cone snails belong. Their ability to specifically target certain receptors has shown huge potential in pain relief.
There has even been a drug brought to market called Ziconotide, which is 1,000 times as powerful as morphine, derived from venom of the magician cone snail. And this comes without the same risk profile that opioids carry, such as potentially lethal respiratory depression.
Research into other applications — such as treating diseases such as Alzheimer's, depression and epilepsy — is ongoing.
Harpoon-shooting Killers
They might not have fangs, but most cone snails 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 Predatory Techniques of the Cone Snails
Some different types of 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 needs to do at that point is follow its prey and gobble it up when it catches up.
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."
Original article: Cone Snail: A Slow but Highly Venomous Predator
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