You've probably heard the expression "truth is stranger than fiction." Well, nothing could be further from the truth. Nature shows us its special capacity and all its power with species of animals that don't seem real, like the man-of-war jellyfishIn this case, we are talking about a species that, although it may seem like a product of fiction, is completely real: the immortal jellyfishIts currently accepted scientific name is Turritopsis dohrnii (historically cited as Turritopsis nutricula in some texts). It has a feature that many people would like to have: the reversal of aging or, in other words, so-called biological immortality.
In this article we are going to talk about the characteristics of the immortal jellyfish and learn more about its secrets, integrating what is known about its biology, its genetics and its scientific value without losing sight of its ecological role at sea.
Key features
This is something that is not common: a living being with a lifeline rejuvenation practically unlimited. This jellyfish has the ability to regenerate itself and restart its life cycle. Every time it is damaged, suffers severe stress, or conditions are adverse, is capable of rejuvenating and healing returning to its juvenile polyp stage. Not only is its regenerative capacity impressive, but visually it's one of the most delicate and beautiful jellyfish.
It has an elongated bell-shaped umbrella of no more than 4 to 5 mm in diameter, making it one of the smallest jellyfish in its adult state. It doesn't need any more size: with its exceptional cellular plasticity and its planktonic lifestyle, it is perfectly adapted. The umbrella is thin, translucent and practically colorless, allowing you to easily see inside.
In the center, a deep crimson digestive system covered by a whitish layer stands out. When the immortal jellyfish reaches its adult stage, it can present around 80 to 100 tentacles short and delicate; in juveniles, however, there are usually one or two dozen. These tentacles are covered with cnidocytes with nematocysts, stinging cells it uses to capture microscopic prey. Its sting is mild and imperceptible to humans.
At the taxonomic level, it belongs to the group of cnidarians (along with corals and anemones) and, more specifically, hydrozoans. Their body is composed around a 95 percent water, a fact that explains its gelatinous nature and buoyancy in the water column.
Habitat and area of distribution
It is not an easy thing to find the location of the immortal jellyfish because of its tiny size and pelagic life. It has been recorded in seas all over the world, with frequent occurrences in the Mediterranean and parts of the Sea of Japan, as well as in the Caribbean and Pacific regions. This cosmopolitan distribution has been favored, among other factors, by passive transport in ballast water of the ships.
In general, he prefers temperate waters although it can tolerate a wide range of conditions. Its presence may go unnoticed and be confused with related species of Turritopsis, since a specific diagnosis requires detailed analysis. The distribution area originally cited in the Caribbean expanded as its taxonomy became better studied, and today it is considered a widespread species.
One of the reasons why it is increasingly detected in more regions is not that it multiplies without limits, but that it combines a high reproductive rate with its peculiar ability to reverse the cycle. Of course, this immortality is biological and does not exempt it from predation, illnesses or accidents.
What is worth mentioning is that they do not die of old age on their own: their end is usually linked to the food chain or disturbances. Even so, as a small planktonic jellyfish, they can evade predators with a certain effectiveness, which, together with their vital plasticity, gives them a survivability notable in coastal and oceanic environments.
Cycle of the immortal jellyfish
Let's analyze the life cycle of the immortal jellyfish. Life begins as a planula larva, like any other hydrozoan jellyfish. After developing, the planula attaches to a substrate and gives rise to a polypThis polyp can form colonies and, therefore, gemmation asexual, releasing tiny jellyfish that begin the pelagic phase.
There are many cases in which the larvae have been found to attach themselves to mollusk shells or hard surfaces on the bottom. As they begin to adapt and settle, they form authentic polyp colonies from which tiny jellyfish emerge. This is how, each time, populations grow and disperse in the water column, where they reproduce sexually (releasing gametes) and close the cycle with new planulae.
Here comes its uniqueness: if a juvenile or adult jellyfish experiences adverse conditions, injury, hunger or stress, it can perform a reversion of its life cycle. That is, dedifferentiates its cells adult cells to a cellular cyst-like state and reorganizes their tissues to form a new cell. polyp functional. This process is called transdifferentiationOnce in polyp form, it can regenerate new jellyfish, genetically identical to the original.
This loop can be repeated numerous times and, unlike other jellyfish that lose the ability to revert after sexual maturity, T. dohrnii can do so even after reproducing. That is why we talk about biological immortality. It does not imply invulnerability: a fish, crustacean, or anemone may devour it, or an extreme disturbance may prevent it from completing the reversal successfully.
At the molecular level, comparative research with closely related species indicates that T. dohrnii present an genetic endowment and expression patterns that favor the DNA protection and repair, efficient management of the oxidative stress, and mechanisms that help preserve the integrity of the telomeresDifferences have also been observed in genes involved in replication and in the regulation of cellular pluripotency pathways, such as the greater representation of certain differentiation factors, including additional copies of GLI-type genes involved in stem cell reprogramming. genetic synergy supports its exceptional plasticity.
Breathing
Many people have doubts about how these animals breathe. Since they don't have a specific organ for breathing, this doubt plagues many. We can only see their stomach through their transparent skin. However, we can't see gills, lungs, or any complex structures. These jellyfish they breathe by diffusion across all of its body surfaces.
Like other simple animals and organisms such as sea sponges, exchange gases with the dissolved oxygen in water thanks to the activity of its own cells. This process is carried out without specialized organs because its surface-to-volume ratio It is very high and its metabolism is low, which facilitates gas exchange.
Although there is usually enough oxygen in the water for all species, no large aggregations are observed of these jellyfish, among other reasons because they would consume the available oxygen from the microenvironmental layer around them. If they accumulate in excess, they will tend to move towards more oxygenated areas, since together they can decrease oxygen and increase carbon dioxide locally.
Food and predators
With just a few millimeters in diameter, T. dohrnii it's a kind carnivorous which feeds mainly on zooplankton: copepods, crustacean larvae, eggs and small prey that it captures with its stinging tentacles. This behavior contributes to the trophic balance of pelagic ecosystems.
Their predators include fish planktivores, small crustaceans y anemones. Therefore, despite its reputation for immortality, it occupies an intermediate place in the food chain and is an important part of the energy flow in the sea.
Main threats
Although it is an immortal jellyfish in biological terms, it also faces threats that can destroy it. The way to reverse the process to polyp only activates if the aggression or stress requires it. If there is a high probability of being eaten, can initiate transdifferentiation towards a renewed youthful state in which its cells reorganize to form a new polyp, from which jellyfish identical to the original will sprout.
In addition to predation, factors such as contamination, episodes of hypoxia, sudden changes in temperature or the presence of pathogens can prevent or hinder reversion. Biological immortality is not absolute: if the damage is massive or the environment does not allow the reorganization phases to complete, the process may fail. Lack of food also limits its survival. maintainability and reproduction.
Scientific importance and what it reveals about aging
The uniqueness of T. dohrnii has attracted researchers from around the world because it offers a natural model for studying the regeneration and cell reprogrammingIn particular, its ability to revert from a functional adult state to a polyp has allowed the identification molecular pathways and genes involved in genome protection, DNA repair, cell division control, and telomere maintenance.
Comparative studies with a close relative, Turritopsis rubra (which does not revert after reproduction), have shown that the immortal jellyfish has more copies of genes associated with repair and stability of the genome and mechanisms of pluripotency cellular. Genes that modulate the oxidative stress and cellular senescence. For scientists, what is extraordinary is not a single magic gene, but the combination of changes acting in a concerted manner.
Does this serve human health? The honest answer is that we are still far from it. extrapolate These processes affect humans. However, understanding how an animal avoids cumulative damage and maintains cellular integrity can inspire breakthroughs in regenerative medicine and in preventing or delaying deterioration associated with neurodegenerative diseases. It also helps to delineate the difference between longevity (living many years with some deterioration) and biological immortality (avoid terminal aging by restarting the cycle).
It is worth remembering that it is not the only creature with regenerative feats: the hydras Freshwater fish can regenerate indefinitely, and other animals such as fish or salamanders repair organs or limbs. However, T. dohrnii It is unique because it reverts from adulthood to a juvenile phase again and again, even after reproducing, which places it in an extreme case of vital plasticity.
The immortal jellyfish combines a tiny size, simple anatomy, and efficient molecular machinery to keep its cells flexible. This combination, coupled with its dual polyp-jellyfish life cycle, allows it to defy aging in a way that captivates science and expands our understanding of how life can thrive. reinvent yourself when the environment becomes hostile.