How Long Do Jellyfish Live? (Are They Really Immortal?)

The lifespan of jellyfish varies by species. Some jellyfish live for only 12 months, while other jellyfish species might survive for up to 18 months. However, this is only true for the final stage of the jellyfish development when it becomes a fully grown jellyfish.

How Long Do Jellyfish Live

Some scientists argue that jellyfish can live forever. In the wild, jellyfish can regenerate and go through a life cycle that enables them to live again and come back as jellyfish.

Some jellyfish species have the capacity to transform themselves into a cyst and become a polyp, initiating the growth cycle again. 

Because of that, they might undergo this cycle multiple times, which leads many people to believe that some jellyfish are immortal. This is only true for the immortal jellyfish or the Turritopsis dohrnii.

Can Jellyfish Live Forever?

A jellyfish species called Turritopsis dohrnii, or the immortal jellyfish, can potentially live forever due to its ability to turn itself into a polyp and start the growth cycle again.

The immortal jellyfish was first discovered in the late 1800s when scientists first started seeing this incredible phenomenon. Since then, it has been discovered that the immortal jellyfish can, indeed, live forever thanks to their special type of development. This is where their name comes from.

This is a very unique case and it only happens in the wild. This happens because immortal jellyfish have a different growth cycle from standard jellyfish.

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Standard Jellyfish Life Cycle:

  1. Fertilized egg – this is when the adult jellyfish will spawn eggs after breeding, so the eggs are ready to hatch.
  2. Larva – the eggs will then grow into a small larva that is called a planula. This planula is very small and it already has the ability to swim freely.
  3. Polyp – the next step is for the planula to turn into a polyp. This polyp will usually settle on the surface and stay there to feed itself in order to grow.
  4. Ephyra – the second to last stage of the cycle is ephyra, which is an independent polyp that can move around freely on its own.
  5. Jellyfish or Medusa – the last stage is the adult stage that we see as a jellyfish. This adult jellyfish will be able to breed and reproduce.

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Immortal Jellyfish Life Cycle:

The immortal jellyfish, on the other hand, have a very different type of growth cycle.

They’re able to stay immortal thanks to the fact that they will turn themselves into a cyst when they are harmed or when they are close to dying, overcoming the final stages of a jellyfish’s life.

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How Long Do Jellyfish Live?

Most jellyfish species will live for between 12-18 months before they perish. 

In the adult stages, jellyfish will survive for up to 18 months. They might take several months to develop from an egg to a fully adult jellyfish, but at the end of the development, the jellyfish will only be able to survive for up to 18 months.

This will vary between jellyfish species, obviously. This is how long some jellyfish species might live:

Jellyfish SpeciesJellyfish Lifespan
Moon jellyfish18 months
Blue blubber jellyfish12 months
Spotted lagoon jellyfish 12 months
Red cross jellyfish 12 months
Blue cannonball jellyfish12 months
Ghost jellyfish12 months
Australian spotted jellyfish 12 months

Note that these time frames are only applicable to jellyfish that live in the wild. In proper living conditions and with the right care, some jellyfish might live for up to 20 years in captivity or even longer.

Jellyfish that are kept as pets, on the other hand, will get better treatment and as a result, might live longer. If you want to extend the lifespan of your jellyfish, then the following tips might help you:

  • Filtrate the water regularly
  • Keep the water quality at a high level
  • Ensure the jellyfish has enough space to thrive
  • Feed your jellyfish regularly and with quality foods

If you manage to do all of those things, then you’re increasing the likelihood of your jellyfish living longer than the times you’ve seen above!

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What is the Oldest Jellyfish?

The oldest jellyfish is the immortal jellyfish. Some scientists believe that these jellyfish don’t really die, but they turn themselves into a cyst and they are reborn.

This jellyfish species has the ability to live forever thanks to its amazing ability to recover and revive itself through a special process. It is unique to this species and scientists believe that immortal jellyfish can live forever if the process is not stopped in one way or another.

As for other jellyfish species, it is not clear what is the oldest jellyfish. You might hear people say that their jellyfish has lived for several years and even up to 20 years, which is entirely possible. This can be achieved with good care and by making sure that the jellyfish lives in the best possible conditions.

The majority of jellyfish, however, will only live for about 12-18 months before dying, which is unfortunate but it’s part of their genetic structure and there’s not much you can do about it.

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How Do Jellyfish Die?

Most jellyfish die as they are brought to the shore by the waves. Then, they will evaporate because the body of the jellyfish is over 90% water.

Jellyfish die slowly and this process will not be very clear. Some jellyfish might be brought up to the water’s surface, while others will continue to float in the water. After a period of time, the jellyfish will not be able to resist the flow of the water, and eventually, they will be washed up on a beach.

Other times, jellyfish are either eaten by predators or they might disappear as they die, but most commonly, they will be brought to the beach.


The majority of jellyfish species will live for between 12 and 18 months, but some might survive longer with proper care.

Immortal jellyfish, on the other hand, can live forever thanks to a special process that allows them to regenerate and live longer. This process is unique to this species of jellyfish.

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