You and I once considered the longest-living organisms on Earth and there was already one immortal. But now I will tell you about one more immortal organism.
They began to talk about the immortality of the hydra back in the 19th century. But the hypothesis was proved only at the end of the 20th. Experimentally, Daniel Martinez demonstrated that due to their high regenerative capacity, some types of hydras are immortal. In a short time, their body can restore individual parts. Due to these features, in recent years, hydra has been used as a model object for studying regeneration and morphogenesis processes.
Let's find out more about it …
Hydra is a small amazing creature and, as it turned out, is actually an immortal creature. The hydra is best known for the fact that if you cut it into several parts, they will eventually grow into new hydras.
The body of a hydra is a bag with a wall of two layers of cells (ectoderm and endoderm). It is cylindrical in shape, at the front end of the body, on the perioral cone, there is a mouth surrounded by a corolla of 5-12 tentacles. In some species, the body is divided into a trunk and a stem. At the posterior end of the body (stalk) is a leg (sole), with its help the hydra moves and attaches.
In ancient Greek mythology, the fantastic creature Hydra of Lernean was a monstrous nine-headed snake, which was considered invincible, because new ones grew in the place of the chopped off heads, and therefore Hercules had to destroy it with great effort. In nature, there is a small aquatic animal, similar in its qualities, which proudly bears the name "hydra" in honor of its mythological "ancestor"
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In the upper part of the cylindrical body of the hydra, only 1−2 cm long, there is a mouth surrounded by a rim of 5−12 small tentacles, with the help of which it constantly hunts for prey, and which have the ability to regenerate in the same way as the rays of sea stars, if these the tentacles are cut or torn off.
This ability of hydras has fascinated scientists for centuries. However, the regenerative capabilities of hydras actually turned out to be much more complex and amazing - something from the realm of fantasy. According to scientists from the University of California at Berkeley, this creature is able to recreate its body even after it has been rotated in a meat grinder.
The aim of the study, led by Ulrich Technau, was to establish to what extent the regenerative capacity of hydras extends. The most amazing thing is that, after going through the knives of a meat grinder, the hydra crushed in puree was enough for the preserved head, and then its hydra body began to form anew. The head was responsible for sending continuous signals to the cells of the rest of the body, ordering them where they should go, and which part of the body they would eventually turn into.
Moreover, scientists have found that after rolling through a meat grinder, small aggregations of cells in the hydra's head are scattered over the remains of the body, and several new independent individuals gradually grow out of them. Thus, the animal did not just repair itself, it could turn into several hydras. These unusual characteristics make the hydra a creature that is almost impossible to destroy.
When cut across into several parts, each part restores the “head” and “leg”, keeping the original polarity - the mouth and tentacles develop on the side that was closer to the oral end of the body, and the stem and sole on the aboral side of the fragment. The whole organism can be restored from individual small pieces of the body (less than 1/100 of the volume), from pieces of tentacles, as well as from a suspension of cells.
Hydra can be regenerated from cell suspension obtained by maceration (for example, by rubbing the hydra through a mill gas). Experiments have shown that the formation of an aggregate of about 300 epithelial-muscle cells is sufficient to restore the head end. It has been shown that regeneration of a normal organism is possible from cells of one layer (only ectoderm or only endoderm).
If you cut out a fragment from the side of the hydra's body and fuse it with the body of another hydra, then three outcomes of the experiment are possible: 1) the fragment completely merges with the body of the recipient; 2) the fragment forms a protrusion, at the end of which a “head” develops (that is, it turns into a kidney); 3) the fragment forms a protrusion, at the end of which a "leg" is formed. It turned out that the percentage of head formation is higher the closer to the donor's head the fragment is taken for transplantation and the further from the recipient's head it is placed. These and similar experiments led to the postulation of the existence of four substances-morphogens that regulate regeneration - the activator and inhibitor of the "head" and the activator and inhibitor of the "leg". These substances, according to this regeneration model, form concentration gradients: in the region of the "head" of a normal polyp, the concentration is maximal as an activator,and the inhibitor of the head, and in the region of the "leg" - the maximum concentration of both the activator and the inhibitor of the leg. All of them were actually discovered.
At the end of the 19th century, a hypothesis was put forward about the theoretical immortality of the hydra, which they tried to scientifically prove or disprove throughout the 20th century. In 1997, the hypothesis was proved experimentally by Daniel Martinez. The experiment lasted about four years and showed that there was no mortality among the three groups of hydras due to aging. It is believed that the "immortality" of hydras is directly related to their high regenerative capacity.
Before the onset of winter, after the transition to sexual reproduction and maturation of the dormant stages, hydras die in the reservoirs of the middle zone. Apparently, this is not due to a lack of food or the direct impact of other adverse factors. This indicates, nevertheless, that hydras have some mechanisms of aging, the cause of which is sexual reproduction.
Well, a few more immortals:
American lobster
This type of lobster has self-healing DNA. A special enzyme called telomerase prevents them from aging. Scientists estimate that the oldest lobster found is 140 years old and has not shown any signs of aging. It is believed that American lobsters are biologically immortal, and they die from external causes.
HeLa cells
Unlike ordinary cells, these cells have the unique ability to divide an infinite number of times. This division is possible thanks to the same enzyme telomerase: it builds telomeres at the ends of the DNA of chromosomes. They were first discovered in Henrietta Lacks' cervical cancer in 1951. HeLa cells are now used to study cancer, AIDS and many other diseases and various substances.