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Are Jellyfish Immortal?

Last Reviewed and Updated on July 7, 2022

Jellyfish are one of the world’s oldest and most unique creatures – they’ve been around for over 500 million years and can be found in every ocean on Earth. But what makes them truly fascinating is their potential immortality! A jellyfish species is believed to be biologically immortal, meaning they never die of old age. So, are jellyfish immortal? Some, theoretically, yes. Let’s take a closer look.

What is a jellyfish?

A jellyfish is a free-swimming marine animal with a gelatinous body and tentacles. They are found in every ocean, from the surface to the deep sea. Some even live in freshwater. Some species of jellyfish are capable of living for hundreds of years, making them one of the oldest animals on Earth. Though they have been around for eons, there is still much to learn about them.

Learn more about them on this list of facts about jellyfish.

The life cycle of a jellyfish

To understand their mortality and potential immortality you need to understand their life cycle. These animals have a very simple body structure and a life cycle that is pretty unique in animals.

Jellyfish go through two major stages in their life cycle. The medusa stage and the polyp stage. The medusa is the free-swimming, adult stage of a jellyfish’s life cycle. The polyp is the attached, immature stage.

Most jellyfish start their lives as tiny polyps. They are attached to rocks or other surfaces in the ocean. As they grow, they develop into medusae and eventually detach from their attachment point to become free-swimming adults.

When conditions are right, medusa jellyfish will reproduce sexually, releasing eggs and sperm into the water to fertilize them. The eggs hatch into larvae which then settle onto surfaces and begin to grow into new polyps. Things get interesting here. Polyps can reproduce as well, they reproduce asexually by budding.

The cycle then begins anew as the new generation of jellyfish grows and matures into adults. They truly are fascinating creatures.

Jellyfish live anywhere from a couple of days to many, many years before they die of old age. But that is not true for all species… There is one very interesting exception.

The immortal jellyfish

There is one known species of jellyfish, Turritopsis dohrnii, commonly known as the immortal jellyfish that is biologically immortal.

This jellyfish has a life cycle like any other jellyfish. It has a polyp stage and a medusa stage. It does most things as any other jellyfish would. But there is something that sets this animal apart.

If this particular species is injured when in the medusa stage, experiences stress, or simply ages enough it will revert back to its polyp stage.

In theory, this process can go on indefinitely. This particular species theoretically isn’t able to die of old age. This pretty much makes them immortal.

Reality tells a different story though as most jellyfish will still die at some point, either by being eaten by predators or because of a disease.

This jellyfish is found worldwide. While this is the only known species of jellyfish with this ability there could be more.

Think this is weird? Do give our list of weirdest facts about animals a read and be ready to drop your jaw.

Are jellyfish immortal?

You’ve got your answers now. The majority of jellyfish species aren’t immortal and will die of old age, if not killed by predators first.

There is one species that is theoretically immortal and can avoid dying of old age, however that won’t stop it from becoming dinner to other animals. Nature is full of surprises.

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