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Maybe Not What You Think

May 19, 2018

The Portuguese man-of-war (Physalia physalis) is infamous for its painful stinging tentacles that can extend up to 10 meters (33 feet) long down from the surface. They are used to catch small fish, usually at night. The man-of-war may look like a jellyfish, but it’s actually a siphonophore. An “individual” is actually made up of genetically identically, but highly specialized, units called zooids: its gas-filled bladder, its tentacles, its digestive units, and its reproductive structures. Although man-of-wars are occasional visitors to Cape Cod, Mass., they are usually found in warmer coastal areas. Many other siphonophores inhabit the ocean’s twilight zone, thousands of feet below sunlit surface waters. (Photo by Larry Madin, Woods Hole Oceanographic Institution)