The Immortal Jellyfish

Did you know that at least one species of jellyfish is biologically immortal? Like, it can live forever?

Before you say "no way!" imagine this: all jellyfish go through a life cycle of two stages, polyp and medusa. (And before you ask: "like Medusa the Gorgon?"--yes, that Greek name made it all the way down to the humble jellyfish. Just like thousands and thousands of other Ancient Greek words which trickled down into English--and all the other Western languages of today.)

Polyps are the immature organisms which reproduce asexually by budding (basically, breaking off) small chunks from the top of the polyp--those "chunks" later becoming medusa, or, mature jellyfish.

Mature medusa (which we usually call jellyfish) then lay eggs, which in turn attach themselves to a solid surface (like coral or rock or seafloor) and grow into a polyp...and the cycle repeats itself.

However, one species of jellyfish, Turritopsis dohrnii, can use a process called transdifferentiation to make itself young again--literally. Basically, whenever this jellyfish is hurt, old, or even hungry (or when you grab it like you're trying to hurt it), it sinks to the seafloor where within mere days it turns into its own "baby" stage--meaning, it becomes a polyp again. It attaches itself to the seafloor or coral or rock--and starts growing and budding fresh new jellyfish. Both the polyp and the "new" jellyfish are actually exact copies of the "old" jellyfish--meaning, they all have exactly the same genetic material. Thus, they are still the same jellyfish. 

Scientists think this jelly can pull this off forever--or, rather, until it's eaten by a predator--like a turtle or shark or another jellyfish.

Nobody knows just how old the oldest jellyfish on the planet is...but it could be, in fact, perhaps thousands of years old. If it was lucky enough not to get eaten in its younger days:)

Click below to watch a really cool documentary on the Immortal Jellyfish:

https://www.youtube.com/watch?v=DSLQYTt8BjA