You say jellyfish, I say jellies — either way, they’re invertebrates (no backbone) made up of 96 percent water, 3 percent protein, and 1 percent minerals. That’s right: no heart, no brain, no bones. But that does not make them any less of a presence on Earth — jelly swarms have single-handedly shut down nuclear power plants by clogging water intake pipes.

Not all jelly-like creatures are jellyfish. To a scientist, true jellies have bell-shaped bodies, tentacles, and stingers. One tentacle could have thousands of stingers. Ouch! Even ouchier is the fact that a stinger releases its poison like a mini-harpoon, with about the same pressure as a gun fires a bullet.

Occasionally jellies sting each other when they’re stressed. It’s kind of like me with my tail during interpretive dance competitions: I am not responsible for what happens, although it’s almost never fatal. What happens after a jelly stings a jelly depends on the species, but one researcher told me for a run-of-the-mill jelly, death results if the sting is large enough.