Not only is it not a jellyfish, it's not even an "it," but a "they." The Portuguese man-of-war is a siphonophore, an animal made up of a colony of organisms working together. The man-of-war ...

It looks like a jellyfish, but it’s not! The Portuguese Man O’ War is one of the ocean’s weirdest and most fascinating creatures, blending beauty and danger in an alien-like form.

That's one of the largest size differences between males and females—called sexual size dimorphism—in the animal kingdom ... the Portuguese man-of-war, which it uses to its advantage by ...