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, then catch and reel in fish for food. After drifting through jellies, one of the most common life forms on Earth, 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.
Update: This is a longer version of the original video.
Related reading: Nomeus gronovii, the man-of-war fish.
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