These Are the Beautiful but Deadly Inner Workings of the Portuguese Man-of-War

by Owen James Burke


Unlike jellyfish, Portuguese man-of-war are active hunters, sailing by the wind with their 30-foot tentacles drawn behind them, seeking unsuspecting prey consisting mostly of small fish and crustaceans. (All Photographs and Video: Aaron Ansarov/Nat Geo)

Aaron Ansarov, a retired combat photographer for the Navy, returned home to Florida and while walking the beaches, noticed the beauty in the blues and purples on the Portuguese man-of-war that washed up on a beach in Florida. Others skittered off in fright, but Ansarov took out his lens and got closer.

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Portuguese man-of-war belong to a group of animals called siphonophores, which are like jellyfish but formed by colonies (like some polyps and anemones) instead of one singular organism. Their DNA is exactly the same, but depending on how the jelly rolls, they’ll each assume their own position and function within the colony.


The blue and purple coils are the tentacles, which work a bit like hypodermic needles: something brushes up against them, and it triggers a small needle with a deadly mix of venom to protrude. Along with that venom comes a digestive enzyme, which immediately begins breaking down the victim’s proteins before even landing in its stomach.

The true deadliness of the Portuguese man-of-war depends on whom and where it makes contact. A small child with a tentacle wrapped around his neck is in serious danger, because a massive amount of the toxin will be absorbed into the bloodstream, while an adult male could be stung across the back and not feel any more irritation than what would come with a few small splinters. (“Women and children have thinner skin than men,” generally, explains Professor Angel Yanagihara who studies toxins in siphonophores.)


Out of all the animals in the kingdom, the Portuguese man-of-war may be exposed to more UV radiation than any. It spends all of its time in open water with no cover at all, and only a thin membranous balloon that faces the harsh sun day-in and day-out. Some scientists believe that it’s purplish-blueish pigments and the variations between act to absorb different wavelengths of UV light and provide the man-of-war with a natural sunscreen. Who knows, Maybe someday we’ll have sunscreen made from them.

See more of Aaron Ansarov’s photo essay on National Geographic — OB

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