The tentacles of the Portuguese Man o’ war (Physalia physalis) are beautiful as they float down into the water… but fish and humans, beware: These tentacles are venomous. They can sting, and they catch and reel in fish for food. Blue Planet II captures this food chain phenomenon with a fish that can’t escape its fate.
The man-of-war comprises four separate polyps. It gets its name from the uppermost polyp, a gas-filled bladder, or pneumatophore, which sits above the water and somewhat resembles an old warship at full sail. Man-of-wars are also known as bluebottles for the purple-blue color of their pneumatophores.
The tentacles are the man-of-war’s second organism. These long, thin tendrils can extend 165 feet in length below the surface, although 30 feet is more the average. They are covered in venom-filled nematocysts used to paralyze and kill fish and other small creatures. For humans, a man-of-war sting is excruciatingly painful, but rarely deadly. But beware—even dead man-of-wars washed up on shore can deliver a sting.
Muscles in the tentacles draw prey up to a polyp containing the gastrozooids or digestive organisms. A fourth polyp contains the reproductive organisms.
Related reading: Nomeus gronovii, the man-of-war fish.