If, like seahorses, starfish look like creatures from a fairytale, the venomous invertebrate known as the crown-of-thorns belongs in one of those old, sinister Brothers Grimm versions.
Crown-of-thorns starfish (or more properly, "sea stars") eat coral reefs. Because of human activities such as overfishing of their natural predators, they can sometimes undergo a population explosion. This, in turn, can result in the complete destruction of a reef. Not only will this mean the loss of habitat for the many creatures that make their home in reefs, but the local tourist industry can be hit too.
To combat the problem, there have been various efforts the kill off the excess crown-of-thorns. On the Great Barrier Reef, for instance, divers started off by chopping the invertebrates into little pieces. The plan backfired because of the sea stars' remarkable ability to regenerate [source: Davis].
Not only can they regrow lost limbs, but under the right circumstances, they can grow a whole new body from a severed limb. That's because their cells are "indeterminate," which means they retain the ability to form new body parts, just as our embryonic cells did when we were first developing [source: Scienceline].
Now, if only we could master this regeneration thing — not only could we regrow lost limbs, we could generate whole new ones. Who couldn't use an extra pair of arms? Things would be a little weirder, though, if those disembodied arms grew a new you.