I know what you're thinking. People give things cute names all the time, names that reference some little trick the animal can do even though you can't take the name seriously or literally. Like the Yak-Killer Hornet, or the Goliath Bird-Eating Spider, or the Soul-Stealing Goat, surely it can't actually do the thing its name references.

Well, the good news is that you'd be completely wrong. The bad news is that the Immortal Jellyfish is probably going to take over the world.

Known by its scientific name Turritopsis nutricula, the Immortal Jellyfish lives its life like any other jellyfish. It is very small, growing to a maximum diameter that is slightly smaller than the nail on your pinky finger. They are believed to have originated in the Caribbean Sea, but have now spread throughout temperate and tropical oceans the world over, likely hitching rides in the ballast of cargo ships.

They grow up just like all jellyfish do. Which is to say, they begin life in polyp form, very small and attached to a surface such as a rock, filter feeding on microscopic particles in the water. They stay this way for a few weeks as part of a polyp colony, and then grow the signature jellyfish tentacles and release from the surface to swim free in the ocean as a fully grown medusa (the adult form of a jellyfish).

In the normal course of things, the jellyfish would then reproduce a certain number of times (different species of jellyfish live a few hours to a few months) and then die, giving way to new generations of squishy little critters.

The Immortal Jellyfish, late one night after a Highlander marathon with his buddies, thought about this whole living and dying arrangement and said, "Dude, that's bullshit." Then he burned the Highlander 2 disc to do the world a favour. Then he became immortal.

Immortality, in this case, means that the jellyfish is actually more like Doctor Who than Connor Macleod of the Clan Macleod. When the jellyfish is threatened by injury, starvation, or some diseases, it regenerates. Full on Doctor Who style regenerates.

The jellyfish absorbs its own tentacles, inverts its bell and absorbs most of that as well, and then literally regenerates every single one of its cells. Each cell is born anew, and might be a completely different cell from what it was before. A brain cell could become a reproductive cell, a tentacle cell could become a brain cell. The jellyfish is born again, brand new, and starts over at the polyp stage. This isn't the jellyfish cloning itself. It simply regenerates its own cells and becomes a baby, starting its entire life cycle over again, giving rise to a new polyp colony.

As far as we know, the Immortal Jellyfish can do this an infinite number of times. This is known as biological immortality. Every single Immortal Jellyfish can do this at any stage of its life, and it can keep giving birth to new Immortal Jellyfish during each and every reincarnation.

The jellyfish can still be killed if it is eaten by something, can still be taken out by some diseases, and there are indications that simple old age does not trigger its regeneration mechanism, but this is not known for certain, nor is it known how long they live naturally in the wild.

In the meantime, the Immortal Jellyfish has used its regeneration technique to create ever greater numbers of its species throughout the world. One scientist described it as "a worldwide silent invasion," and another jokingly said that the Immortal Jellyfish would someday conquer the world through sheer numbers. Then he laughed, nervously, and glanced at the ocean. He swallowed visibly and took the rest of the day off.