Tag Archives: man-of-war

Man-of-wars are 1 animal, not a mishmash of critters

Published September 17, 2016 in the “Ocean Watch” column, Honolulu Star-Advertiser ©2016 Susan Scott

At the beach, I recently ran into my neighbor, Marya, who, as usual, had a thoughtful marine animal question. She wondered how it is that a Portuguese man-of-war is a colony of individuals rather than one animal.

“I can’t picture how that works,” Marya said.

I can’t picture it, either, but we don’t need to because it’s an old idea. Besides that, the confusing colony statement detracts from the fact that the Portuguese man-of-war is one of nature’s most exquisite masterpieces.

A man-of-war starts life when a drifting sperm meets a drifting egg and grows into a larva, a flat bean-shaped thing with swimming hairs.

As it matures, the front end of the larva transforms into a blue, air-filled bubble topped with a fleshy pink sail that the creature trims to move at an angle to the wind. When strong tradewinds and storms overpower the little sails, man-of-wars get shipwrecked on our beaches.

While forming its float, the larva also produces, from below, three types of tentacles. One type contains sperm and eggs (man-of-wars are hermaphrodites). Another kind has long tentacles with stinging cells. The third tentacle type consists of hollow eating tubes.

As the creature sails around the ocean surface, its stinging tentacles troll below for small crustaceans and fish. When it gets a catch, the retractable tentacles reel it in to the eating tentacles, which wrap around the food.

Normally having openings invisible to the naked eye, the mouths of man-of-war eating tentacles can expand to three quarters of an inch. After spitting enzymes on the prey to externally digest it, the food tubes suck up the meal.

Most animals function similarly, having a nerve-directed team of genetically identical, but specialized, organs dependent upon each other to live and reproduce. But because the man-of-war grows its float and tentacles by budding (pooching out) from its larva, some biologists in the past declared that each pooch was an individual animal, even though each does a different job and none can live alone. It’s like saying our stomach is one person, our gonads another and limbs another.

Although the statement that each man-of-war is a colony rather than an individual is pervasive, it’s not written in stone. My favorite invertebrate zoology textbook authors write “ … that it sometimes seems more appropriate to consider the colony (of siphonophores, man-of-war and their clan) as one complex individual.” And the authors of my Monterey Bay Aquarium go-to book on gelatinous animals write that although it’s still debated, “ … most specialists now prefer to think of (siphonophores) as individuals with many well-integrated parts.”

Now that we can picture. Thanks, Marya, for another great question.

Portuguese man-of-wars run aground in high wind

Published March 11, 2013 in the “Ocean Watch” column, Honolulu Star-Advertiser ©2013 Susan Scott

A Portuguese man-of-war blown onto a beach. ©2013 Susan Scott

My walk down the length of Kailua Beach on a recent blustery day brought back memories of another windy day there in 1983. Marine animals were new to me at the time and every day at the beach felt like Christmas.

“Look, I found something amazing,” I said to Craig one afternoon, showing him my treasure. Between thumb and forefinger I held a transparent bubble 2 inches long topped with a pink ruffle. A fringe encircled the bubble like a blue tutu, and below that, fluttering in the breeze, hung the creature’s tail.

Craig, a seasoned ocean-goer, laughed.

“It’s called a Portuguese man-of-war, and that’s no tail. It’s a stinging tentacle. It’s probably not a good idea to carry it around.”

I didn’t carry it for long. I put it in a bucket of seawater. Afloat, the creature came alive, slowly extending its tentacle into the water as if sighing with relief.

I couldn’t wait to get home and learn more about this strange creature with the odd name, and I’ve been learning about them ever since.

Fortunately for me, the balloon part of the stinging Portuguese man-of-war, a jelly­fish relative, is safe to touch. It’s this smooth transparent sac, containing mostly carbon monoxide, that enables the animal to float on the ocean’s surface.

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Along the length of the float lies a blue or pink crest. During periods of calm weather, the crest flattens and the animal drifts with the current. But when the wind blows, the creature sets sail, raising its crest to cruise at a 45-degree angle to the wind. In this way, the Portuguese man-of-war, named after 16th-century battleships, trawls for fish.

Stinging cells line the tentacles (some individuals have more than one) that trail beneath the animal’s float. Acting like tiny harpoons, the cells shoot a paralyzing toxin into the prey. Once a fish is immobilized, the tentacles draw it up to the creature’s mouth, also located under the float.

Normally, Portuguese man-of-wars float offshore throughout the world’s tropical and subtropical waters. We see them, and sometimes feel the pain of their stings, when the wind overpowers their tiny sails and the animals get blown into our bays and onto our beaches.

As a fellow sailor, I feel a tinge of sadness when I find these little anglers lying on a beach. The last thing in the world Portuguese man-of-wars want is to be blown off course and shipwrecked.

Craig was right about handling them, though. It’s not a good idea, because even when these creatures are beached, their tentacles retain the ability to sting.

I don’t carry Portuguese man-of-wars around anymore (usually). But I still see them as amazing gifts from the sea.


Marine biologist Susan Scott writes the newspaper column, “Ocean
Watch”, for the Honolulu Star-Advertiser, www.staradvertiser.com

©2013 Susan Scott