Secrets Of The Immortal Jellyfish

Did you know that the longest-living animal on Earth is a creature called the immortal jellyfish? Just from the name alone, we might assume that it could escape death a few times. For real though, they could, in theory, of course. The adult versions of these invertebrates can roll back their biological clock when injured or on the verge of starvation:

However, while this is technically feasible, it’s by no means provable. That’s because these jellyfish have only been studied sporadically since the early 1980s, meaning experts have only a few decades’ worth of data.

There’s also another factor to consider. While an immortal jellyfish can age in reverse, it can also be easily killed by predators including various fish, sharks, turtles and even other jellyfish. This is why the immortal jellyfish is unlikely to overpopulate the Earth anytime soon.

Normally, a mere mortal jellyfish passes through five stages of life:

Fertilised egg: an adult jellyfish (known as a medusa) will spawn eggs and sperm into the water, with these two types of cells joining up to create a fertilised egg.

Planula: the fertilised egg grows into a small larva called a planula. It looks something like a microscopic worm and can swim about freely.

Polyp: The planula will swim down to find a solid surface (such as a seabed), where it will develop a digestive system and is able to feed itself. When conditions such as water temperature suit it, the polyp will reproduce asexually, cloning itself to create a small colony.

Ephyra: after forming a new set of muscles and nerves, a section of a polyp (either the original polyp or clone) becomes an ephyra, an organism that can swim independently, grow and feed.

Medusa: this is a fully-grown adult jellyfish, which can reproduce sexually with another jellyfish (usually dying shortly afterwards).