Siphonophores are marine invertebrates that look like a single organism but actually consist of a colony of many individual animals.

Portuguese Man of War   ©  Magnus Lundgren

Some siphonophora superficially resemble jellyfish, like the best known species of this kind:
The dangerous Portuguese Man o’ War.
Others form one of the longest animals in the world, reaching up to 50 metres in length.

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