If you could be any living thing other than a human, which would you be and why?

 Turritopsis dohrnii (The Immortal Jellyfish). I would like to be this creature because it is really fascinating to me, it is literally immortal unless you eat it or it is killed in other ways. 

How this works is that the Jellyfish starts as a Larva, like a newborn, then a Polyp, a baby, then a Strobila, which is like an adolescent, and then Epgyra like an adult. This sounds like a normal life right? Not immortal, mortal, but when the immortality comes in is when the Jellyfish is under stress. This makes the Jellyfish consume itself and switch back and forth through life stages. So in theory the Turritopsis dohrnii is really immortal.