The whole variety of forms of adaptive reactions of living organisms is divided into two groups. Instincts have developed as adaptations to constant and periodic environmental phenomena.
The second group unites the types of behavior that animals have found in individual life, more precisely, what each beast has understood and suffered with his own mind. These reactions help the body adapt to unexpected, rapidly changing conditions of existence.
Both forms of adaptive activity include successive series of actions aimed at achieving beneficial results for organisms. However, programming of such actions within an innate and acquired activity can be carried out in different ways.
Golden Eggs of Wasp and Aplis Snail
As a rule, instinctive activity is based on rigid programs. Studying the life of insects, the outstanding French naturalist J. Fabre drew attention to an interesting form of instinctive behavior of the yellow-winged wasp - sphex.
At a certain stage of development in these wasps, under the influence of internal hormonal changes and environmental factors (primarily air temperature and day length), egg maturation begins. There is also a need to postpone them. This stage of behavior of the carnivorous wasp is a typical example of instinctive activity.
The wasp begins by digging a certain shape in a secluded place. Then it flies away to hunt for game, which should serve as food for the larvae as soon as they hatch from eggs. The game for sfex is a field cricket. Sfex detects a cricket and paralyzes it with powerful stings in the nerve nodes. Pulling him to the hole, the wasp leaves him near the entrance, she herself goes down to the hole to check the situation.
After making sure that there are no strangers in the hole, the wasp drags its prey there and lays its eggs on its chest. She can also drag a few more crickets into the hole in order to seal the entrance with them. Then she flies away, and she will not return to this place.
If you carefully consider all the stages of the behavior of a wasp, you will notice that all its movements are deployed according to a unique program subject to a single result - egg laying. Scientist J. Fabre many times pushed back the cricket, which the wasp left at the entrance during the inspection of the hole. In this case, having got out of the hole and noticing that the prey was too far away, the wasp grabbed it again, pulled it to the entrance, and then descended into the hole, but again alone. The wasp tirelessly repeated all the actions: it dragged the cricket, then dropped it, checked the mink, to return again after it.
So, in the behavior of a wasp, each previous result of its activity, aimed at achieving a milestone result, determines the development of the subsequent action. If the wasp does not receive a signal about the successful completion of the previous stage, it will never proceed to the next.
All this suggests that the behavior of the wasp is built according to a strict program. It is triggered by inner need, motivation. But the implementation of the program is determined by the staged and final results of the adaptive activity of the animal. What it is, the following observations show. After the wasp walled up the entrance, you can literally destroy her efforts before her eyes. The fate of the eggs is no longer of interest to the wasp, since its mission has been completed.
This whole program is determined by hereditary mechanisms. After all, the descendants of the wasp will never meet with their parents and learn nothing from them. However, these hereditary mechanisms come into effect only in the presence of certain environmental factors. If the wasps do not find them, say soft soil for minks, the whole chain of actions gets confused and breaks. And then a whole population of wasps in this ill-fated place dies.
It seems that all forms of instinctive activity are being built.This was confirmed by scientists who studied on all continents and in the abyss of the seas and oceans the manners and habits of winged, four-legged, scaly, pinnipeds, earth-moving and other our neighbors on the planet.
The wider the manifoldness of the instinctive behavior of animals was revealed to man, the more captivatingly he was attracted to him by the greatest secret of living nature. What are the internal properties of the body instincts based on? After opening in 1951-1953. J. D. Watson, F. Crick and M. Wilkins of the structure of DNA, this question has been concretized, and now it sounds like this: how are innate behavior encoded in genes and how do they control it?
The most vivid and informative answer to this question was given by a group of American neuroscientists led by E. Candel. They examined the same form of behavior in aplizia sea snails as in sfex - egg-laying. The laying of aplizia eggs, the participants in these experiments tell, is a cord containing more than a million eggs. As soon as under the influence of contracting muscles of the duct of the hermaphroditic gland, where fertilization occurs, the eggs begin to be pushed out, the snail stops moving and eating. Her breathing and heart rate increase.
The snail grabs a cord of eggs with its mouth and, moving its head, helps it out of the duct, and then twists it into a skein. Finally, with a movement of the head, the animal attaches the masonry to a solid base.
E. Kandel and I. Kupferman found in the abdominal ganglion (i.e., the accumulation of neurons) aplisia so-called axillary nerve cells. An extract was obtained from them and introduced into the body of other snails. And it turned out that the power of some substances from this extract over the behavior of the mollusks was so great that the snails immediately began to lay their eggs, even if their maturity had not yet come. Moreover, unfertilized snails, having received such an extract, made separate movements from the egg-laying ritual.
Scientists are interested in the substances that make up the active principle of the extract of axillary cells. They turned out to be 4 peptides (i.e. short chains of amino acids), one of which was called GOY - the egg-laying hormone. Just note that this discovery was not a complete surprise. Among other biologically active substances, peptides are now being studied most intensively.
After all, these tiny proteins, acting in negligible amounts, regulate almost all vital processes of the body: nutrition, respiration, secretion, reproduction, thermoregulation, sleep, etc. The number of peptides isolated from different tissues has already exceeded 500. Many of them are synthesized in nerve tissue and directly control behavior.
The role of the "axillary" peptides of aplizia was also the same. American scientists found 7 neurons in the aplsia nervous system, on which these peptides have the most powerful and selective effect. According to biologists, these 7 cells act as command neurons. In other words, they control the remaining nerve cells of aplisia, which are part of the functional system that provides the laying of eggs. In any aplosis, these cells under the influence of “axillary” peptides begin to simultaneously generate electrical impulses, and the sound of their electrical “speech” in this case is completely different than in other cases when these neurons give an electric “voice”.
In addition to launching these command neurons, the four peptides from axillary cells also had other professions that were closely interfaced for the sake of one ultimate goal - egg laying. One peptide slows the heart rate. Another cuts the duct of the hermaphroditic gland so that the cord comes out. The third suppresses the appetite of the snail so that the gluttonous mother does not dine with her own offspring.
From the reproductive system of the cochlea F. Strumwasser and his colleagues isolated 2 more peptides. They were called peptide A and peptide B.It was they who forced the axillary cells to secrete the four peptides that were just described. Thanks to this discovery, the mechanisms for launching a functional egg-laying system have become clearer.
Thus, it was confirmed that it was the peptides that “assemble” nerve cells into one working association, selecting from the set of possible neuron compounds those that are subject to their action, and including them in functional systems. Together with neurons, peptides also combine peripheral cells into a commonwealth. As a result of the peptide-coordinated activity of all this huge cell ensemble, a useful behavior result is achieved.
It would seem that everything here is logical and thoughtful. But in fact, a very important issue remained unresolved until neuroscientists began to work with decrypted genes.
By whose “order” did the entire four peptides begin to be secreted by axillary cells in strict order? Under the action of peptides A and B? Of course. But after all, these substances only launched a mysterious mechanism in the axillary cells. So how does he act?
This question is very important. After all, it was worth this sequence and proportionality in the allocation of peptides, and it was based on it that the hard programming of the instinctive behavior of aplisia was built, at least in some way to break, and she would not lay any eggs. Obviously, this would also happen with Spex, where the “handwriting” of some group of peptides is also guessed.
Neuroscientists first suggested and then proved that the nature of the synthesis of peptides from one functional group entrusts one and the same gene, or at least several genes, but is closely interconnected by a commonality of regulatory mechanisms.
Using genetic engineering methods, American researchers have identified and fully established the nucleotide sequence for the three aplisia genes. The first "printed" in a strictly defined sequence the four peptides of axillary cells. Two other genes synthesized peptides A and B. Analysis of the nucleotide sequence of these genes revealed duplicate sites. This indicates that all three genes come from the same precursor. During evolution, he was probably mutated. For example, the number of copies of this gene could increase (duplicate). Due to new mutations affecting already newly formed genes, they began their own evolution. As a result, duplication of genes through the formation of new peptide families led to an increase in the number of body functions, for example, congenital behavior programs.
It is difficult to overestimate the importance of this work for biology. It was possible to develop and continue the idea of a system-forming role for peptides. It became clear how they mediate the action of "general collectors" of functional gene systems on different cells. The evolutionary path leading from genetic mutations to the multiplication and complication of instinctive behavior programs has become clearer.
However, no matter how tempting these hypotheses were, they still needed to be confirmed on animals other than aplisia. Only then could one speak of the universality in nature of the principle of control over the whole body reaction of one gene encoding a group of functionally linked peptides. And this has already been done.
American scientists N.I. Tublitz and his colleagues proved that several interconnected genes encode a group of peptides that control the final stage of tobacco moth metamorphosis - the exit of an insect from a pupa. This tough behavioral program launches one large peptide. It is synthesized in the nervous system and begins to be released into the blood two and a half hours before hatching the moth. Climbing out of the pupa, the insect spreads its wings. Three other peptides control these processes. Two of them contribute to the filling of the blood vessels of the blood vessels, from where it flows into the blood vessels of the wings and spreads them.The third peptide acts on the connective tissue of the wings. While they straighten, he gives them plasticity, and then - constant rigidity.
From 1980 to 1983, in the laboratories of Professor S. Num (Japan) and Dr. P. Seburg (USA), the sequence of the gene printing the preproopiomelanocortin protein was established. In the brain, this huge molecule is cut by enzymes into several short chains - peptides. In animals and humans, preproopiomelanocortin peptides form a single functional system. We are all familiar with its action. Thanks to her, our body responds to strong and unexpected stimuli with an innate reaction - stress.
One peptide from the preproopiomelanocortin family increases the secretion of glucocorticoid adrenal hormones. They, in turn, increase blood circulation in the muscles, enhance their contractility, increase blood glucose. Another peptide stimulates the breakdown of fat. Due to glucose and fats, reserve energy is mobilized. The third peptide enhances insulin secretion and ensures the use of glucose by tissues. The fourth extinguishes the pain. That is why even severe injuries during excitement, stress, we do not notice immediately. Thus, nature makes it possible for living things in an extreme situation to complete the main thing, and then do "self-healing". Finally, the latter peptide increases attention and the level of wakefulness of the brain, which is also useful in any life situation.
So, truly “golden eggs” brought scientists sphex and aplizia. Watching in the last century the behavior of a carnivorous wasp, J. Fabre discovered the main external patterns of innate behavior. After about a century, American neuroscientists have generally outlined the molecular genetic mechanism by which the brain stores and implements programs of innate behavior.
However, work in this direction has only just begun. Indeed, the innate behavior of mammals, which is the ultimate goal of all studies of brain science, is in fact never so hard-coded as the reactions of sphex, aplisia or tobacco moth. The significance of environmental factors that J. Fabre observed while observing a predatory wasp in the instinctive behavior of warm-blooded animals is incomparably greater. And accordingly, the principles of genetic control are more complicated, more plastic and in some ways already different.
