The immortal jellyfish
Living things gradually fall apart as they age. This is because at a cellular level, cells stop
dividing and functioning normally and eventually die. This process is known as senescence. But what if we could escape this process and reach immortality? There is only one species that can do this, the Turritopsis dohrnii, a small, transparent jellyfish.
To understand how the Turritopsis dorhnii is biologically immortal, first, we need to understand the life cycle of a jellyfish.
First, the fertile medusae, adult jellyfish, lay eggs. The eggs then hatch into planula larvae which then swim to the ocean floor and embed themselves into the soil. They become benthic polyps and develop. They then detach themselves and become ephyrae, free swimming jellyfish. The ephyrae become adult medusae and the cycle starts again.
So, everything seems normal. This seems to be a standard life cycle. This particular jellyfish must die at some point, right? In the case of the Turritopsis dorhnii, when the jelly fish begins to experience senescence, it turns into a clump of cells, embeds itself back onto the sea floor and turns back into a polyp.
By reverting to an earlier stage of its life cycle, the Turritopsis dorhnii has officially escaped the process of senescence and has reached biological immortality.