Is a Portuguese man o' war a Jellyfish?

The Atlantic Portuguese man o' war (Physalia physalis), also known as the man-of-war, is a marine hydrozoan of the family Physaliidae found in the Atlantic, Indian and Pacific Oceans. Its long tentacles deliver a painful sting, which is venomous and powerful enough to kill fish or (rarely) humans. Despite its appearance, the Portuguese man o' war is not a true jellyfish but a siphonophore, which is not actually a single multicellular organism (true jellyfish are single organisms), but a colonial organism made up of specialized individual animals (of the same species) called zooids or polyps. These polyps are attached to one another and physiologically integrated, to the extent that they cannot survive independently, creating a symbiotic relationship, requiring each polyp to work together and function like an individual animal.

 

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