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We all face the fact that, sooner or later, we grow old. Despite our attempts to trick time, aging is part of life. There are nevertheless some animals that can delay or escape the passage of time.
The immortal jellyfish
The Turritopsis dohrnii is a 4.5 mm long jellyfish that was discovered in the Mediterranean Sea in 1880 and it is known as the immortal jellyfish. The life cycle of a jellyfish begins with a fertilized egg that grows into a planula. The planula then develops into a polyp, which is cylindrical in shape and is attached to a substrate. It then matures into a jellyfish, and for most of these animals this is the final stage of their development… but not for the Turritopsis dohrnii! When it faces stress factors like injury, it reverts to the polyp phase.The mechanism behind it is called “trans-differentiation” : cellular differentiation is the process in which a stem cell matures into a highly specialized one. Non-specialized cells can give rise to multiple cell types, while adult cells can’t. Trans-differentiation is particularly interesting for scientists in stem cells research, because it could help them replace damaged cells.
The forever young hydra
The animals belonging to the genus hydra are microscopic freshwater organisms, with a tube-shape body and a mouth surrounded by tentacles (like the polyp phase of the jellyfish life cycle); they were named by the scientist Linnaeus in 1778 after the Lernaean Hydra, because of their ability to regenerate a severed part of their bodies. In the past, it was hypothesized that hydrae were capable of escaping senescence (the gradual deterioration of the normal functioning of a cell) and being potentially immortal, but no data were published to support this hypothesis until 2012. A group of scientists from Germany discovered that hydrae’s unlimited life span depends on the ability of its cells of continuous self-renewing thanks to a particular set of genes called FoxO.
The indestructible water bear
The tardigrades, also known as “water bears” or “moss piglets”, are a group of 8-legged micro animals first described by the German scientist J. Goeze in 1773. The interest on them grew when a French scientist, Raoul-Michel May, shoot X-rays on them at doses 500 times higher than the ones that would kill a person. Amazingly, almost all the tardigrades of the experiment survived. Since then, scientists have tested the effects of other dangerous rays on them like gamma ray: they can survive levels of radiations many times higher than what occurs on our planet. Not only can they resist radiations, but they can also survive at really low temperatures and outer space. Their secret is that they can repair their DNA. They have the Dsup (damage suppression) protein that forms complexes with DNA protecting it from breaking, and this hasn’t been found in any other animal so far.
Aging is associated with changes in our physiology, psychology, and environment. We should accept it as part of life, but animals with superpowers like jellyfish, hydra and tardigrades can help us to understand more about the physiology of our bodies and give us tools to cure some diseases (with stem cells research)!
Author: Francesca Abela
Buddy: Christina Isakoglou
Editor: Ellen Lommerse
Translator: Marlijn ter Bekke
Editor translation: Floortje Bouwkamp