This Ancient, Regenerative Animal May Hold the Secret to Reversing Old Age

Scientists often encounter things beyond human comprehension. When studying jellyfish and their remarkable healing abilities, a team of scientists dealt with this very concept. When a thriving adult jellyfish undergoing study appeared to be replaced by a larval jellyfish, scientists couldn’t hide their befuddlement. Where did their adult jellyfish go, and how did an infant jelly come to be?

This is the unfathomable story of comb jellyfish and how they can age in reverse. This is what their regenerative abilities mean for the future of humanity.

“As if They Were Going Back in Time”: Adult Comb Jellies Revert to Larval Stage

Also known as ctenophores and considered one of the most ancient animal lineages, comb jellies possess the unique ability to revert to larval stages after reaching maturity. This was discovered in 2024, after scientists were prompted by the question: are there any creatures on earth capable of immortality?

Studying comb jellies made sense to scientists given the existence of Turritopsis dohrnii, also known, ironically, as the immortal jellyfish. This unique species was once the only creature on earth capable of returning to a polyp stage after stress, injury, and drastic changes in its environment. However, the comb jelly also demonstrates this very same ability and the scientific promise it holds.

When studying comb jellies, scientists induced both minor injury and starvation in their fully-grown, healthy, adult test subjects. In a matter of weeks, the team couldn’t believe their eyes: these adult jellies completely reverted to a cydippid or adolescent form. The once-adult jellies behaved the same way as cydippids do, fully reverting to a juvenile stage.

How did this happen? Why are comb jellies capable of this? And what does this impressive discovery mean for aging humans?

How and Why Comb Jellies Display Developmental Flexibility

Much like the immortal jellyfish, comb jellies demonstrate regenerative and de-aging life cycles. However, the reasons why this can occur at all are still unclear.

Scientists studied the effects of injury and starvation on nearly 70 adult comb jellies. When injured, the jellies reversed to juvenile stages faster and more completely compared to the jellies who were merely starved. However, starved jellies still began the de-aging process, returning to the life cycle that directly follows a larval state.

Both immortal jellies and comb jellies achieve reversals in aging thanks to the presence of certain stem cells. While the specific cells responsible for regeneration and reversal are not yet identified, cell transdifferentiation occurs and activates both the expansion and transformation of genes within both species.

Other Animals Capable of Aging in Reverse

There are many different classifications for developmental flexibility and regeneration in animals. Comb jellies are rare in their ability to completely revert to a larval stage when placed under stress or uncertain circumstances. However, other creatures in the animal kingdom have regenerative potential in other ways, such as regrowing limbs, organs, or entire bodies.

These animals have regenerative potential worth studying, as they are capable of harnessing their cells and molecular basics in a way humans cannot.

Newts

Studied for decades, newts remain impressive and impossible examples of bodily regeneration. Not only can newts regrow their limbs and tails, but they can also reproduce their organs and eyes. In fact, newts kept in scientific studies and placed under repeated regenerative circumstances maintain youthful DNA and cell structures. This suggests newts do not lose regenerative capacity as they age and are in fact capable of living for decades, as many of these newts were studied for nearly 30 years.

Earthworms

Regardless of the specific species, all earthworms have segmented bodies. When these segments are dissected or removed from the primary body, two distinct regenerative capacities can occur. Some earthworms can regrow tissue and return to their adult size, while others split into two distinct earthworms after dissection. The species and location of the dissection affect this outcome, but stem cells are at the core of these processes.

Demosponges

A large class of sea sponge, demosponges of many distinct species are capable of regenerating their bodies. Some can return to their full capacities after losing a portion of their spongy selves, while others achieve restoration with only half or a quarter of their original body remaining. The regenerative capacities of sea sponges are well-known and vital to the commercial sponge industry.

Stick Insects

Much like lizards, stick insects are prone to shedding their limbs in order to escape predators. They also regrow legs during molting processes. While this is an impressive feat, studies suggest this process may affect the overall strength and size of the stick insect’s wings. This suggests risks and a certain level of tradeoff a stick insect must undergo whenever their limbs are lost.

Octopuses

Capable of regrowing both limbs and nerves, octopuses are a fascinating regenerative study. Many scientific investigations conclude octopuses are unbothered by nerve damage or dissection, hunting and exhibiting normal behaviors shortly after surgery. Likewise, their abilities to regrow and reconnect nerves are unparalleled; the only side effect octopuses experience is an occasional lack of chromatic ability at the site of injury.

Will Science Make it Possible For Humans to Age in Reverse?

Only time will tell if scientific advances will make it possible for humans to age in reverse or slow aging processes. While multiple studies cite the importance of stem cell research and its potential for regeneration, plasticity, and cell communication, there is still ample research to be done.

Our scientific potential increases with each passing day. Our futures are uncertain in terms of anti-aging techniques but, with stem cell research and further study of these remarkable animals, we may see a day where human beings achieve regenerative, ageless feats.