Jan 172010
photo provided courtesy of 3Neus on Flickr Creative CommonsHometemperate and tropical seas worldwide
Habitatocean surface
Nichepassive predator
Favorite Foodsmall fish
Lengthup to 100 feet
Notable Featurethe whole is composed of thousands of individual organisms

Although it looks like a jellyfish, the Portuguese Man-o-War is actually a colony of living organisms that band together to form a highly efficient killing machine. These organisms, called polyps, each perform a specialized role in order to keep the whole outfit floating, killing, eating, digesting, and reproducing in the world’s oceans.

The Portuguese Man-o-War is so named because of the projection on its float bladder that resembles the sail of a centuries-old warship. This sail catches wind on the surface of the ocean, which is the only way the colony can move. The Man-o-War has no means of locomotion and can only float. It’s at the mercy of the sea breeze and ocean currents, and if either of these forces drives it onto the seashore, it’s done for. However, as long as it remains at sea, it is a formidable predator.

Although it’s not technically a jellyfish, the Portuguese Man-o-War nonetheless hunts like one. It boasts dozens of dark purple tentacles that can trail behind the bladder in the water for over 60 feet. Like a net trolling behind a boat, these tentacles are used to kill and ensnare prey. Each one is studded with tiny cellular weapons called nematocysts. Each contains a trigger mechanism, a coiled spring, and a deadly barb. When an unsuspecting fish brushes up against one of the Portuguese Man-o-War’s tentacles, it flicks the trigger and the trap is sprung. The coiled spring unfurls in a fraction of a second, driving the venomous barb deep into the fish’s body at high velocity. Toxins in the barb attack the fish’s nervous system, paralyzing it. The polyps specializing in digestion take over, secreting powerful enzymes to break down the fish for the good of the colony.

Although it can’t run, fly, or even swim, the Portuguese Man-o-War is nonetheless one of the most feared hunters in the temperate and tropical seas of earth, delivering stings powerful enough to land an unwary diver in agony. They are also prime examples of the fascinating possibilities of working together in the natural world.