Communication of living organisms
The world of animals is diverse, and each existing species in its life uses a rather complex and peculiar signaling. Among the various ways of transmitting information in the animal kingdom, smells play a significant role. Animals and plants give specific signals with the help of volatile molecules, without which the normal life of these organisms is impossible. Such chemical communication is a general biological phenomenon and occurs in representatives of various stages of the evolutionary ladder: from bacteria to humans. Moreover, as signals, animal organisms use a very diverse set of chemical compounds that serve as a kind of alphabet of this language. Often, information is encoded not by any one substance, but by a mixture of odorous molecules.
Along with the sense of smell, living beings use sight, hearing, touch and other organs of perception and transmission of information, which, depending on the level of development of the organism, can play a different role in communication. However, most scientists believe that chemical signaling using odors is one of the most ancient ways of communicating and exchanging information between living organisms.
Cell-Signaling-Pathway Example:
And how many unsolved secrets are connected with the chemical language of animals! Often, these mysteries inspired not only researchers, but also science fiction writers. Thus, in one of his novels, Clifford Simak painted a picture of the capture of our planet by space aliens, who imperceptibly began to interfere in the laws of the development of human society. Remaining incognito, they brought the earthly civilization almost to the brink of disaster. It would seem that a sad end is inevitable, but at the last moment, the Achilles' heel of aliens was discovered. The insidious plans of aliens from outer space were violated by a small fluffy animal - a skunk. It turned out that the smell emitted by skunks has a magical property to attract invisible enemies. The molecules of this substance deprived the invaders of their minds, and they discovered themselves. Leaving all their claims and forgetting about the purpose of the visit to Earth,
The writer's fantasy is based on a real-life phenomenon, because odorous molecules really play an extremely important role in the life of some animal species.
Most of us, some from stories and some from our own experience, are familiar with the smell of musk. This pungent substance is secreted by the glands of the male musk deer, which attracts the female to it. In addition to this animal, which lives in the mountains of Central Asia, the American skunk emits a similar smell.
There are other volatile compounds that living organisms use for their "chemical conversations". The alphabet of smells in the animal world is complex and varied. Odorous molecules attract a male to a female and, marking the boundaries of their “possessions”, create a kind of odor barrier for intruders, and also serve as invisible landmarks for relatives, allowing them to find each other in the wilds of the surrounding world. Using chemical signals, animals report danger during the invasion of enemies, and if necessary, the "chemical telegraph" helps to gather "compatriots" in one place.
In order to distinguish the whole variety of these mysterious molecules from a huge number of other chemical compounds, scientists after a long debate decided to call them pheromones. This most commonly used term was formed by combining two Greek words pherein (transfer) and horman (excite, stimulate). Pheromones are volatile substances synthesized and released into the environment by living organisms. These chemical compounds cause specific behaviors in individuals of the same species.
Currently, scientists have found trace and alarm pheromones in animals, as well as sexual and aggregative odorous substances. In addition, pheromones were discovered - territory markers.
Intercellular communication between artificial cells by allosteric amplification of a molecular signal Example:
How many beautiful lines have been written about the amazing abilities of our four-legged friends - dogs to search for criminals on the invisible scented tracks. In experiments, dogs were able to easily distinguish even members of the same family, if there were no identical twins among them. So, for example, if the bloodhound was allowed to sniff the things of one twin who did not participate in the experiment, she confidently followed the trail of the other.
The dog can serve not only as a bloodhound or watchman. It has been established that, in addition to aliphatic acids (butyric, valeric, etc.), her nose smells of natural hydrocarbons. Using a dog's sense of smell, experts quickly identify a leak in a gas pipeline and prevent accidents.
Who now does not know about the phenomenal ability of salmon and eels to find their native places, moving away from them thousands of kilometers deep into the oceans? It is possible that flocks of fish navigate in the ocean by the sun and currents, and when swimming to their native shores, by the smell and taste of substances dissolved in the water. These landmarks help the inhabitants of the seas and oceans to take care of procreation, overcome all obstacles, and reach the spawning site.
According to some reports, the sense of smell in fish is 3-5 times finer than in dogs. In addition, they can detect the presence of vital compounds up to 20 km away. Experiments have shown that fish are not indifferent to the minute amounts of amino acids contained in the water. Scientists suggest that combining them with other substances gives the river or lake that special native smell that helps migrating fish find their way home.
In various species of living organisms - from bacteria and plants to humans - odors play an important role in life. Let us remember what joy the intoxicating aromas of flowers and perfumes, the mysterious smells of the sea and forest bring us. And how appetizing fresh bread or fragrant tea smells, giving us strength and uplifting mood.
Specialists who deciphered the individual chemical components of the aroma of fresh bread got into a difficult situation. Previously, it was assumed that the smells of freshly baked bread are determined by two substances: maltol and isomaltol. However, when mixing these substances, the desired aroma did not appear. What's the matter? It turned out that other chemical compounds also create the smell of bread. Chemists have discovered more than 200 of them. The search continues, and the appetizing aroma has not yet been reproduced.
The imitation of food smells is one of the most important areas in science, which will help to make tasty and aromatic food in the laboratory.
Many representatives of the animal world also look for food by smell. Predators sniff thousands of square meters of living space in search of food, deer find moss under the snow with their sense of smell, and bees find “delicious” flowering plants by smelling landmarks.
Already at first glance, it becomes obvious that a rat will distinguish its relative from a mouse, and the latter will not confuse its relative with a cat. In this case, we are dealing with interspecies relationships. And what is the role of odors in closely related animal species?
The pheromone memory of a mouse, as studies by Soviet scientists have shown, contains information about dozens of familiar relatives from other clans. However, there is also a family pheromone, with the help of which relatives recognize each other. It is interesting to note that unfamiliar males always compete with each other, but if they have been in the atmosphere of the smell of a person caring for them, they begin to behave less aggressively.
In Ukraine, two related species of mice are known: synanthropic brownies and mounds, which got their name because they lay stocks for the winter in earthen mounds - mounds. Studies by scientists have shown that a noticeable reaction in animals is observed only to the smell of representatives of their own species. House and mound mice perfectly distinguish their compatriots by olfactory signals.
In addition to mice, different types of lemurs and American white-footed hamsters distinguish their relatives well. It is also surprising that Kurgan mice can distinguish between male and female house mice by smell, and vice versa. But this is not the limit. Currently, in the laboratories of the world, scientists breed more than 200 different genetic lines within the same species. It turned out that by smell, mice are able to distinguish between animals not only of their own line, but also of an isogenic one, which differs in only one pair of genes.
Not only mice, but also insects, such as male Drosophila flies, are able to distinguish females of their line from females of another due to differences in the ratio of sex pheromone components.
In the mouse kingdom, odorous molecules influence the ability to reproduce and maintain intraspecific constancy. Each group has its own smell, and the female will never mate with a stranger, moreover, if a pregnant female is placed in a cage where a male from another group is located, then her pregnancy will be terminated (the smell of a stranger is enough for this).
Not only mice use pheromones to mark individuals of the same group, but also rats and sea lions. A newcomer with an unfamiliar smell, who has fallen into such a “collective”, will not be accepted by relatives until he acquires “his own” smell. Often the inconsistency of the smell portrait leads the stranger to death. Such is the relationship in fish, as well as in rabbits, rats and other mammals.
Employees of the A. N. Severtsov Institute of Evolutionary Morphology and Ecology of Animals of the USSR Academy of Sciences performed many interesting experiments to elucidate the nature and functions of mammalian pheromones. In particular, scientists were engaged in elucidating the nature of the chemical signals that an individual belongs to its species in the absence of visual and acoustic methods of communication. It was found that the pheromone, by which the male house mouse recognizes the females of his species, consists of three groups of substances: bases, acids and neutral compounds. Removal of one of them violates recognition, the presentation of the "smell passport" of each of the substances separately does not cause the corresponding behavioral response.
It has been suggested that the pheromones of mammals serve for them, by analogy with visual images, as peculiar odor or olfactory concepts.
One biblical legend tells how the wise King Solomon spoke with animals and birds, crawling creatures and fish. A magic ring helped him to talk with animals. At present, in order to study the language of animals, scientists from the Institute of Evolutionary Morphology and Animal Ecology of the USSR Academy of Sciences, Moscow State University, the Institute of Bioorganic Chemistry of the USSR Academy of Sciences and the All-Union Plant Protection Institute have joined forces in a single program "Pheromones". Researchers involved in elucidating the laws of chemical language hope to work together to learn how to control the behavior of animals.
More and more data is being obtained by scientists about the role of smell in marine and freshwater animals. Polychaete worms, which change their sex several times during their lives, secrete special substances that determine whether individuals are male or female. The odorous molecules inhibit asexual reproduction in tubellarian flatworms and ensure egg-laying when at least 200 individuals gather.
Argonaut octopuses breed interestingly. To continue the race, the male donates his tentacle, which carries the spermatophores that fertilize the female. But the most curious thing is that this detached limb finds the female by the traces of molecules dissolved in water.
In addition to sex pheromones, substances that help animals navigate the world around them play a special role. To secure their territory, males and females mark their “possessions” with special substances. Gerbil mice use the secretion of a skin gland located in the middle of the abdomen. This procedure is performed by the male. The odorous secret includes a whole set of chemicals: esters and acids, alcohols and carbonyl compounds.
Representatives of the marten family guard their homes even more strictly. Throwing a fetid secret consisting of mercaptans and disulfides over a long distance, these animals create a chemical barrier for uninvited guests.
The strong smell of the secret of odorous glands, except for the skunk, is possessed by the striped hyena, house polydent and black-tailed deer. Although the number of known chemical signals found in mammals is large, most animals in social life use a similar set of volatile compounds. Thus, male pronghorn antelope secrete a number of alcohols with a long chain of molecules and short-chain organic acids, using them to mark their territory. Similar substances are used by male gerbils for the same purpose. These compounds have also been found in the exocrine secretion of the musk turtle, which uses them to deter predators.
Marine iguanas live on the Galapagos Islands, feeding on algae growing in shallow water. At low tide, they return to the shore, using odorous marks for orientation in the area. Crawling on the rocks, these animals lick up chemicals and use the olfactory recess in the palate to determine their location. Observations of scientists have shown that iguanas are able to detect their home by smell within a radius of 300...400 m.
Young arctic foxes and squirrels, settling in the tundra, use ready-made marks left by previous generations. To mark the territory, animals use the secret of special glands. So, ferrets and badgers, ermines and marmots, ground squirrels and foxes, wolves and dogs leave marks with anal glands. Lemurs rub their soles with urine, and the male blackbuck leaves a strong-smelling black waxy secretion on tree branches. A resinous, characteristically smelling mark is left in the places of forest development, on the paths at the entrance to the water beavers. In the Middle Ages, even medicinal properties were attributed to this “beaver stream”.
Along with individual marks, animals also have “group” or “family” smells. Such marks are known among wolves and deer, sables and ermines, which use such signaling to collectively protect their possessions from uninvited guests.
In his life, a person practically does not use smells in the communication system. However, special experiments have shown that, despite this, the potential of a person in chemical communication is quite large. So, for example, babies from the age of two months can recognize their mothers by the smell and distinguish them from other nursing women. The fact is that with age, a person does not lose these unique abilities. Three- and five-year-olds were as good at identifying their mothers by smell as were newborns. In turn, mothers are just as good at distinguishing their babies from other babies by smell.
The main sources of odor in humans are sweat, the secretion of the apocrine glands located under the armpits, as well as the odorous secretions of the fatty glands. It is interesting that pure apocrine sweat practically does not smell, and the smell appears only after its decomposition by the bacterial microflora of the skin. Among the substances included in human skin secretions and determining its individual smell, one can note such unsaturated fatty acids as butyric, propionic and valeric, caproic and caprylic. As for the smell of the trail, by which the dog will perfectly find the owner, in addition to butyric acid, it also contains a number of aliphatic acids, phenols, indoles, skatoles and other compounds. Moreover, the combination of some of them leads to an increase in the “smell portrait”.
As you can see, smells play an important role in human life. Despite the fact that the sense of smell in the process of evolution gave way to vision and the hearing aid, the emotional perceptions of many odors have also been preserved. Some of them depress us, cause anxiety or some unpleasant, albeit vague memories associated, it would seem, with negative images and circumstances that have been erased from our memory a long time ago. But perfume compositions often evoke visual images: a flowering meadow or the golden ears of a grain field, the cool silence of a forest edge or the endless blue of the sea. Still undiscovered possibilities lie in the use of these invisible signals in the management of a person's mental state.
Of the odorous substances, the most studied are the pheromones of insects using this ancient method of communication. This is not surprising, since the six-legged inhabitants of the planet are one of its oldest inhabitants. In addition, the multiplicity and diversity of different species contributed to the development and complexity of relationships in the world of insects, requiring them to have a fairly large "vocabulary" to explain with their own kind.
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