3 ‘immortal’ animals that have fascinated scientists for decades

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From ancient myths to science fiction literature, our fascination with eternal youth is well documented.

But there are creatures that seem to have deciphered the formula for stopping, or even reversing, aging — and they are very real.

They are, or we believe they may be, biologically immortal. This means that unless they are killed by a predator, disease or drastic changes in their environment, they can live indefinitely.

Scientists are trying to unlock the secrets of these mysterious organisms to see if they can help us control our own aging process.

The following are three of these amazing creatures:

the planarians

The ability of these worms to regenerate by dividing in two has been known since the late 19th century. But these animals went viral in 2012, when the University of Nottingham, UK, published a study on their potential immortality.

The planaria is a type of flatworm that is found all over the world and has an unlimited ability to regenerate stem cells.

There are two types of planarians: some reproduce sexually and others asexually, dividing in two.

Scientists at the University of Nottingham studied both types and found that those who practice asexual reproduction are able to “rejuvenate” their DNA.

At some point in our lives, our DNA, like that of most animals, reaches its limit of cell division, and our bodies begin to deteriorate.

Planarians, on the other hand, have higher amounts of an enzyme that protects their cells from aging — and can replenish these reserves when they reproduce, leading scientists to believe they may be immortal.

the hydra

This alien-looking creature is a freshwater invertebrate with a tubular body and tentacles around its mouth.

It uses these tentacles to sting its prey, which are worms, small crustaceans and other invertebrates.

Hydras were one of the first organisms examined by Dutch scientist Antonie van Leeuwenhoek, who built a microscope with a single spherical lens with significant magnification to observe these creatures.

Shortly thereafter, Swiss scientist Abraham Trembley’s observations of hydras and their “regenerative superpowers” ushered in a new era in biology.

Like planarians, hydras are also capable of regenerating parts of their body. The secret to understanding their potential immortality lies in their stem cells, which can self-renew indefinitely.

In fact, a hydra’s entire body appears to be made up of self-renewing stem cells.

Scientists who have observed groups of hydras for years have not been able to detect any signs of aging in them.

In 2018, researchers at the University of California Davis in the US hypothesized that hydras might be immortal thanks to their ability to control something called transposon genes, also known as “jumping genes”.

These are genes that can “jump” from one part of the genome to another, giving rise to mutations.

When we are young, our bodies are able to control these genes, but as we age, we have a hard time keeping them under control.

Hydras, on the other hand, may be able to repress these genes forever.

Turritopsis dohrnii: the immortal jellyfish

The so-called immortal jellyfish — or, to use its scientific name, Turritopsis dohrnii— lives in marine waters.

First discovered in the 1880s in the Mediterranean Sea, it can now be found in many other places due to ballast water dumped from ships.

It is tiny and loves to eat plankton, fish eggs and small molluscs.

What is amazing about this type of jellyfish is that it can restart its life cycle. When under stress, it regresses to an earlier stage of development.

For comparison, it’s like a frog turning back into a tadpole or a butterfly turning into a caterpillar — and it’s due to a process called transdifferentiation.

Transdifferentiation happens when a fully formed specialized adult cell changes into another type of adult cell. This process remains a mystery to scientists.

It does not stop there.

When the jellyfish reverts to its previous life stage as a polyp, it also creates more organisms with the same genetic code — so basically, as it rejuvenates, it also clones itself.

This text was published on the BBC News Brazil website.

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