July 4, 2024, 9:58 am | Read time: 4 minutes

Some animals seem to have hit the immortality jackpot. PETBOOK presents three animals that use clever strategies to prevent themselves from decaying.

The immortal jellyfish: Turritopsis dohrnii

One of the animals that are considered immortal is the jellyfish Turritopsis dohrnii. It belongs to a group of animals that comprises 3000 to 5000 species of cnidarians, also known as hydrozoans.

These animals normally go through several stages in the course of their lives. The fully developed medusa releases fertilized cells – and dies some time later. Subsequently, small planura cells and later polyps develop. These will then become adult medusae.

However, the immortal jellyfish is different. It goes through a shortened process and never becomes a fully grown medusa. Instead, it sinks back to the ground as a ball of cells and forms a new polyp shape. This is because the immortal jellyfish engages in transdifferentiation. This means that its halved chromosome sets independently reproduce missing DNA through meiosis.¹

Tardigrades

Since their discovery, these microscopically small creatures have fascinated scientists. Not only do they not have a heart, lungs, or blood circulation, but they also breathe through their skin and have transparent blood. They are found almost everywhere: at the height of the Himalayas and in water at depths of at least 4500 meters.

In addition to an appearance that resembles a crushed vacuum cleaner bag with claws and a maw, tardigrades have developed a clever strategy for living an “eternal life”. They need a thin layer of moisture to coat them, but they can also survive for a long period of time without it. If they “dry out”, they simply go into a state of anhydrobiosis and, when moistened again, come back to life. Even after going for a “walk” through space.²

Freshwater polyp Hydra

Many freshwater polyps also repeatedly renew themselves from the inside out. For this reason many are considered potentially immortal. Polyps of the species Hydra are particularly notable as they, like the mythological monster, replace lost body parts with two new ones. Their “head”, located in their center, could actually be called immortal. Under laboratory conditions, the probability of a Hydra dying does not increase the older they get. Instead, they often reproduce through unisexual reproduction.³

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What about axolotl and olm?

None of these animals are truly immortal. If eaten, they, of course, die. However, they still use clever methods to prevent the natural aging process and stay forever young. Their stem cells allow them to potentially regenerate indefinitely. This is a key factor in their regeneration process.

Tailed amphibians, such as the axolotl and various olms have enormous self-healing powers. They can even regrow body parts and organs, including parts of the brain. This is possible because their stem cells are preserved, as they spend practically their entire life in a larval stage.

This is why they are also considered potentially immortal animals. How old these shy cave dwellers can get, however, is yet to be properly researched. Olms that are 100 years and older, however, do not show any signs of aging. In contrast, axolotls kept in aquariums live to a maximum age of 25 years. Whether this is only due to the fact that an aquarium does not provide them with the dark and quiet environment they need has yet to be researched. The average lifespan of olms cannot yet be determined due to a lack of data.

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