15 Facts About the Lion’s Mane Jellyfish

The stunning—and stinging —lion’s mane jellyfish ( Cyanea capillata ) ranks among earth’s most beautiful creatures. Let's tip our scuba masks to this amazing invertebrate.

By comparison, the largest recorded blue whale was a paltry 108 feet long. But don’t go around calling this jellyfish the world’s longest animal. Some marine biologists claim the saltwater bootlace worm ( Lineus longissimus ) deserves that title —when fully extended, it can stretch 180 feet from end to end!

Jellyfish have a very special opening designed to perform double-duty as both a mouth and an anus . At least they’re economical.

As you can see in this clip (filmed by National Geographic), lion’s mane jellyfish need to watch their backs around famished anemones. Also, leatherback sea turtles have been seen gobbling them up off the coasts of Canada. The reptiles' throats contain backward-pointing spikes called oral papillae to help move food in the direction of the stomach ; they also make escaping pretty difficult.

Large individuals are often red or purple, while smaller specimens tend to be shades of tannish-orange.

June 16, 2010 was a weird day for New England beach-goers. Somewhere between 50 and 100 swimmers were stung off the coasts of Rye, New Hampshire and, when a 40-pound lion’s mane corpse was found at the scene, the authorities felt they’d found their perpetrator. But could a solitary jellyfish really inflict so much mayhem?

“It’s certainly not common,” marine biologist Sean Colin told LiveScience , “but it’s certainly within the realm of possibility because they do have so many tentacles if they’re that large.” Colin hypothesizes that, since dead jellies can still sting, maybe the body was broken up into several large chunks which spread out and contacted unsuspecting visitors. We’ll probably never know for sure.

These are arranged in eight sets that contain between 70 and 150 individual tentacles apiece. Now there’s some Grade-A nightmare fuel…

As far as being awesome is concerned, nature doesn’t need the Internet’s help. Perhaps you’ve seen this photo, which happens to be Google Images’ number one search result for “giant jellyfish.” Many blogs and news sites have claimed that this thing is an especially-large lion’s mane jellyfish. But so far as we know, this species has a maximum diameter of only seven and a half feet—far smaller than the monster pictured here. What gives? As you might have guessed, it's Photoshopped .

Believe it or not, one type of jellyfish may be functionally immortal . Sadly, the lion’s mane jelly doesn’t follow suit .

Geir Friestad , Flickr

Frequent denizens of harsh, Arctic waters, lion’s mane jellyfish are seldom seen below the northern 42nd parallel. Also, they gravitate towards the surface and almost never venture beneath depths of 66 feet.

Jellies take on several forms in their complicated life cycles . Upon entering what’s called the “medusa” stage and becoming “adults,” they can reproduce by releasing sperm and eggs. However, as stationary entities rooted to the ocean floor while in the “polyp” stage, they’re capable of asexually cloning themselves.

Derek Keats , Flickr

In all fairness, contrary to popular belief , these animals do have central nervous systems—a ring of nerves can be found nestled in their “ hoods ” (or “bells”). So there.

Though the jury’s still out , many have argued that—due to factors like over-fishing and rising global sea temperatures—jellyfish numbers may be skyrocketing . Who knows? If true, this might mean we’ll all start munching on more dried jellies at seafood restaurants.

C. capillata sometimes swim together in huge, kilometer-wide clusters called “shoals.”

While deadly to smaller animals (including other jellyfish), lion’s mane jellyfish stings don’t have much of an effect on fish of the Caranx genus , which actively seek the invertebrates out and hover near their tentacles for protection.

Scott Sherrill-Mix , Flickr

The world’s greatest detective had never faced a squishier adversary. In The Adventure of the Lion’s Mane (1926), he deduces that an unlucky professor had been stung to death by one of these spineless predators—which he proceeds to track down and flatten with a boulder. No word on whether or not we’ll be seeing Benedict Cumberbatch go toe-to-tentacle with one.

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