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Guess what, it’s time for another episode of Weird Biology! Today we’re going to learn about a creature that looks like an alien stained-glass window who stalks the oceans with toxic might, powered only by the wind like a sailing ship of old.

That’s right, it’s the devil’s own shopping bag-

(The name is almost longer than the animal.)

The Portuguese Man o’ War (not to be confused with its smaller and less dangerous Pacific cousin, the Bluebottle) is a floating jellyfish relative called a Hydrozoan. It was named after the 18th century sailing ship, apparently by a blind person. “Oh, it looks like a sailing ship under full sail” No it doesn’t, shut up. It looks like a rogue walmart shopping bag that blew into the Atlantic and makes a living by strangling innocent sea turtles.

But like the aforementioned plastic bag, the Man o’ War uses its lovely blue-purple air sac to catch the breeze. It wanders in groups through the warm waters of the Atlantic, driven along by the wind and tides. Kind of poetic, really. As long as you don’t look underwater, anyway. (I’m about to ruin this for everybody, hang on.)

Like so many other things in life it’s not what you see on the surface that’s important, but what is underneath that counts. In this case, what’s underneath is up to 165 feet of venomous tentacles. It’s like that thing they say about icebergs, where you only see the top 10% and the rest is an invisible ship-killing nightmare? It’s exactly like that.

Except with poison tentacles.

The Man o’ War is basically a biological fishing trawler, trailing these stupidly long tentacles like a fine mesh net through the water. And when an innocent fish who probably has a family at home comes into contact with this “net”, specialized cells called Nematocysts are triggered to fire tiny poison harpoons into the victim, causing instant death or paralysis. The tentacle then reels itself upward into the body of the Man o’ War like a fishing line, dragging its helpless victim upward to be digested. So, uh, actually not like a fishing trawler then, not like a fishing trawler at all. (Unless the fishing trawler was designed by Junji Ito.)

Although the Man o’ War may look like a jellyfish, it’s definitely not. In fact, it’s not even a single animal! It’s actually four separate organisms jammed into a venomous trenchcoat like a bunch of best friends trying to sneak into an R rated movie. “How even”, I hear you say. And that’s a valid question! It’s not everyday that we discover that what we thought was a single animal is actually four smaller animals living communally to form a larger, more dangerous animal. It would be like discovering that opossums are actually comprised of 17 rats each.

In the Man o’ War’s case, these four individual kinds of “polyps” that comprise the complete final form are the air sac polyp (gets the gang around), the digestive polyp (converts murdered fish into energy for the whole gang), the reproductive polyp (makes small clones of each individual gang member), and the tentacle polyp (murders things indiscriminately for the sheer joy of it). That’s right, the tentacles are a separate animal! You might be wondering if they sometimes come loose, wander off, and just sting people/animals randomly when they drift into populated areas. What a silly question! Yeah, happens all the time.

(OH NO.)

While only occasionally fatal, Man o’ War stings can seriously injure humans. This is a big problem in areas where Man o’ Wars are common, because storms and predators can knock those tentacles right off. The tentacles then drift away, only to wash ashore and sting a hapless beachgoer weeks later. That’s right, rogue tentacles can still sting for days or weeks after separation! Even if the Man ‘o War is beached and dead! Isn’t that neat! I want to go home!!! The discovery of a beached Man o’ War usually closes the entire beach, for this reason. Would YOU want to go mess around in the sand if it might be full of over a hundred feet of poison spaghetti?

And if all this information upsets you, I’d like to offer my deepest condolences. But buckle up for one last upsetting fact, and here it is: the Man o’ Wars are spreading. Usually restricted to warm waters, climate change has driven the Man o’ War as far north as Great Britain. That’s awful awful awful news for any country that touches the Atlantic ocean, which is lots of them.

Luckily, we have (semi) dependable allies in this fight: sea turtles and the Mola Mola! Unfortunately just about all we can do at this point is support conservation programs for these awesome devil-balloon-munchers, who are endangered themselves. While trying to invent a Man o’ War-proof barrier net.

So for now, just watch out for anything that looks like a floating plastic bag.


1. Bill Hubrick, Maryland Biodiversity Project

2. Jio Ito, Flickr

3. Volkan Yuksel, Wikimedia Commons

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