Giant Jellyfish Grow up to 8 Feet Wide With 60-foot Tentacles

The lion's mane jellyfish can deliver a nasty sting. It slowly descends over its favorite foods — tiny crustaceans, small fish, smaller jellyfish like moon jellies — which become trapped in its sticky tentacles.

Those tentacles are outfitted with stinging cells called nematocysts, which release neurotoxins into the prey to immobilize it. The jellyfish then uses its frilled arms to scoop the prey into its mouth.

The sting of the lion's mane jellyfish is a danger to some and a boon to others. Tiny sea creatures like juvenile whiting (a type of cod) and juvenile walleye pollack find safe haven amidst its tentacles. They don't get caught in them — and their predators steer clear of the lion's mane — so they can hide behind the jelly strings without worry.

Despite its stinging skills, the lion's mane jelly does have predators. Sea turtles, who aren't bothered by its neurotoxins, hunt them. And if a lion's mane jellyfish floats too close to a wall of sea anemones, it's in danger of suddenly being eaten alive.

Lion's mane jellyfish can be found swimming in the Northern Hemisphere, in the cold waters of the Atlantic Ocean, Pacific Ocean and the North Sea.

While climate change is making life harder for many marine animals, most jellyfish — including the lion's mane jellyfish— are thriving as the waters warm. With changes in the environment, researchers believe that the lion's mane's habitat might even triple in the coming years.

These days, there are more lion's mane jellyfish sightings in places like Cape Cod and Nantucket, Massachusetts, the Gulf of Maine and off the coast of Ireland. That means these giant jellies now come into contact with human populations more often.

Jellyfish don't pursue humans, but the unlucky swimmer who gets too close to the Cyanea capillata will get a painful sting.

Ignore the Old Wives' Tale

You may have heard that if you get stung by a jellyfish, you can pee on the affected area (or get a ride-or-die friend to do so) to neutralize the venom. Bad idea. Urine can make the sting more painful and might even prompt any attached barbs to unleash more toxins into your body.

The best remedy is to douse the spot with vinegar to remove any tentacles, then apply a heat pack. Most people won't need medical attention, although some have been hospitalized after tangling with a lion's mane. Symptoms like sweating, stomach cramps or nausea are signs you should see a doctor.

The lion's mane jellyfish's tentacles can keep on stinging, even if they become detached from the jellyfish's body. So if you find a tentacle on the shore, resist the temptation to touch it.

Like other jellyfish, the lion's mane has no brain, but it manages just fine without one. It can eat, swim great distances, reproduce and retreat in defense, thanks to a complex nerve network running throughout its body.

Jellyfish also have no heart, because they have no blood to pump. They don't have any bones either, just a free-flowing, shape-shifting bell and body made of 95 percent water.

As impressive as the lion's mane jellyfish may be, it doesn't stick around for long, living only about a year.

Like all jellies, the lion's mane jellyfish reproduces both sexually and asexually. When they're ready to reproduce, usually from March to May, the male releases sperm through its mouth and the female catches them.

Those sperm fertilize eggs within pouches on the female's oral arms. They soon become tiny larvae, called planulae, eventually leaving the pouch and land on the ocean floor.

Next, the larvae grow tentacles and become polyps. These tentacled polyps, called scyphistomes, munch on sea plankton and — this is where asexual reproduction comes in — reproduce themselves. They eventually grow into the giant jellyfish that have enchanted so many.