Heracles fought with her, she terrified people and was famous for her immortality, because instead of a severed head, a new one immediately grew up in her. It is, of course, a multi-headed hydra. But not the Lernean that kept the ancient Greeks at bay, but about her relative - a completely harmless freshwater hydra.
Material Content:
The structure of freshwater hydra
The tubular and elongated hydra body can reach a length of 1 to 20 mm. One end ends with a basal disk, simply put, with an elongated leg. It is here that a sticky fluid is released that helps the hydra adhere to various surfaces. The other end of the body of the polyp is equipped with a mouth surrounded by tentacles in an amount from 1 to 12. Each of them is filled with special cells that secrete special toxins that can immobilize prey.
The body of the polyp is covered with 3 layers: the outer and inner shells (ectoderm and endoderm), which include nerve cells, and a gelatinous matrix, separated from the first two layers by the skin-muscle layer.
The inner lining also contains various muscle cells, allowing the hydra to contract and stretch. There is also a gastrointestinal cavity, which includes not only the digestive tract, but also the vascular system. This layer also contains cells responsible for the propagation of a freshwater polyp.
It is interesting. The organism under discussion is a small intestinal creature, therefore it is rather difficult to detect it with the naked eye, although it is possible. It is easiest to monitor it with a microscope and a magnifier.
Polyp habitat
Hydra can be found in slowly flowing or completely standing water of lakes, ponds, river backwaters, which is rich in vegetation.
It is interesting. In the reservoirs of Russia, polyps of four species live, which visually practically do not differ from each other. This is ordinary, stalked, stemless and brown hydra.
Some of the varieties of polyps have a green or brown body color. This factor is due to the presence in their body of zoochlorella - symbiotic algae. You can track such hydras by collecting water from a lake in a glass jar along with duckweed floating on its surface. When this water settles, on the walls of the can you can track thin brown, green or white tubes, which are nothing but freshwater hydras.
How animals eat
According to the method of nutrition, freshwater polyps are predators.
The main diet of hydra is composed of aquatic invertebrates (water fleas, plankton, various small insect larvae, etc.). While eating prey, the body of the polyps is lengthened to a maximum, after which they begin to slowly expand the tentacles. Interestingly, the latter, expanding, can exceed the length of the hydra body by 5 times. Stretched out, the tentacles vibrate, waiting for contact with prey. When it occurs, special tentacle stinging cells begin to sting the victim with poison and entwine it.
After a few minutes, the hydra draws its prey into its body and the digestive process begins. A polyp is able to stretch the walls of its body to digest prey twice its size. After a few days, food debris unsuitable for digestion is eliminated through contractions of the mouth opening.
Propagation method
There are 2 forms of propagation of hydra:
- Asexual. With the onset of summer, a bulge forms on the body of the polyp. Growing gradually, it acquires tentacles and a mouth. This peculiar process is associated with the “parent” with a thin thread, which breaks with time, after which the young individual begins to exist independently.
- Sexual. Ovum and sperm develop in the fall. Having met, the germ cells create a fertilized egg, from which a new hydra appears in the spring.
It is interesting. After the death of the polyp, spermatozoa leave his body.
Nervous system and respiration
Hydra has a nervous network, but it has no brain. The accumulation of nerve and sensory cells is localized in the zone of lengthening of the mouth and stem. These creatures are able to respond to electrical and mechanical stimuli, temperature and light. But the hydra’s nervous system is relatively simple. Nerve cells connect with sensory cells, which allows them to transmit signals and respond to stimuli.
It is interesting! If you touch the freshwater hydra, for example, with the tip of a needle, nerve cells instantly transmit a signal to the epithelial-muscular. The latter will react with immediate reduction, and the hydra will immediately compress into a lump.
Respiration and excrement in polyps occurs through the epidermis.
Regeneration and Growth
Distinctive, and in some places even the amazing ability of hydra is the possibility of regeneration. So, in a polyp divided into two parts, new tentacles and a sole quickly grow.
Zoologists have repeatedly conducted experiments with a polyp. So, in the 17th century, a Dutch teacher by the name of Tramble did not only collect whole hydras from pieces, but even get new individuals from halves of different polyps. In addition, the scientist even managed to turn their bodies inside out, as well as receive a seven-headed creature, very reminiscent of the mythological Lernean hydra, which, according to legend, Heracles fought with.
It was after such experiments that the polyp was called hydra.
Life span
But if the hydra has such impressive regenerative powers, does it mean that it is immortal?
At the end of the XIX century, a version was really put forward about the immortality of this polyp.They tried to refute or prove this theory for the next century. Finally, in 1997, a scientist by the name of Martinez experimentally proved the absence of mortality in 3 groups of hydra subjects. The experiment lasted almost 4 years, and its results directly related this feature of polyps with their ability to regenerate.
Another researcher by the name of James Woopal was inclined to confirm the results of the Martinez study, having conducted a number of his own experiments. So, over many years of painstaking work, he conducted an experiment with more than 2000 hydras. The polyps lived in truly royal conditions: each had his own habitat, they were fed regularly and changed the water in the aquarium three times a week. The scientist noted that for almost 8 years of observation, the hydra mortality rate was approximately constant, i.e. 1 case per 165 individuals per year. At the same time, the age of the creatures did not play any role (40-year-olds lived in the laboratory).
Of course, one should not discount the natural living conditions of polyps: the world around it with its diseases, predators and other dangers. Thus, talking about eternal youth and immortality of polyps is not necessary.
Nevertheless, hydra was and remains the most interesting object for studying the mechanism of aging and its absence.
The tiny hydra is the subject of close observation and heated debate among scientists for several centuries. Did this creature really discover the secret of eternal youth? It is likely, because the ability of these polyps to self-healing is truly amazing. Perhaps in the very near future, the mystery of hydra will be solved, and people will learn how to apply the mechanism of slowing aging on humanity.
