Marine mammals. Interesting facts about marine mammals Enemies in nature and threats from humans

Some marine animals can go without oxygen for quite a long time. For example, a sperm whale diving almost a kilometer deep, the air supply that it inhales before that is quite enough to make such a deep dive, and seals feel quite comfortable for at least half an hour without life-giving gas.

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For a long time, scientists could not understand how they manage to do this, but more recently, British experts seem to have figured out this issue. Paradoxically, electricity plays a major role in this. The researchers set out to study the composition of myoglobin, a protein that binds oxygen necessary for the functioning of mammalian muscles. It turned out that in animals such as seals and whales, it has a truly unique property to accumulate a large amount of oxygen, and without any damage to the body. Experiments conducted by Dr. Michael Berenbrink, who works at the University of Liverpool and the Institute of Interactive Biology and published in the scientific journal Science, allowed him to conclude that marine animals are able to accumulate much more oxygen than land animals, which is primarily due to the peculiarities of their natural environment a habitat. According to the scientist, main task was to understand why, at high concentrations in the organisms of marine animals, proteins do not “stick together”.

It turned out that their molecules have the same electric charge (positive), and therefore repel each other. This "physico-chemical trick" allows marine animals to accumulate large amounts of oxygen, since the molecules "work" autonomously in this respect and do not waste their resources interacting with each other. According to Dr. Berenbrink, they, like the same poles of different magnets, repel each other. It is this feature, which appeared as a result of evolution, that allows marine animals to store oxygen in much larger volumes and much faster than land animals are capable of doing.

Leading researchers are of the opinion that this important discovery will allow them to thoroughly understand what changes have occurred in mammalian organisms in general and in their individual organs throughout their development. With a change in habitat, the processes of respiration have changed significantly, allowing animals to exist in completely new environments for them. natural conditions. It should be noted that this has been evolutionary for millions of years, and at its core, marine animals have retained the original method of assimilating oxygen, having significantly “modernized” and improved it.

What mammals live in the sea?

Mammals are warm-blooded and cannot breathe underwater. However, some of them millions of years ago went in search of food in the sea. Their descendants adapted to the new living conditions and became outstanding swimmers. Their limbs have turned into fins, and a thick layer of fat has formed that protects them from cold waters. Marine mammals include whales, dolphins, seals, sea cows (sirens) and sea otters (sea otters).

How does the blue whale eat?

The blue whale is the largest mammal on our planet, reaching a length of 35 meters and weighing about 135 tons. However, this giant is quite harmless and feeds on small marine crustaceans called krill. To get enough, he has to intensively absorb krill, in summer - up to 4 tons per day. Blue whale filters crustaceans from sea ​​water with the help of a whalebone - thin 4.5-meter horny plates located on the upper jaw instead of teeth.

Which seals are the largest in the world?

Southern elephant seals are the largest pinnipeds on the planet. Male individuals reach a length of 5 meters and weight up to 4000 kilograms. Females are half the size and lighter. These giants live mainly on the islands around Antarctica. Northern elephant seals are much smaller and live along the west coast of North America.

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Which of the land animals is a relative of the siren?

Sirens are the only marine mammals that are vegetarian. They eat algae that grow in the warm, shallow waters of the Atlantic Ocean. It is even hard to imagine that these marine animals are distant relatives elephants. Depending on the species, they reach a length of 2.5-4 meters and weigh 250-1500 kilograms. They are not as big as their earthly relatives. Sirens always keep to coastal and often very shallow waters. Sirens are the manatee and the dugong.

Which mammals cannot leave the aquatic environment?

Whales and sirens are not able to leave the aquatic environment, although their ancestors, who lived many millions of years ago, could do this. They emerge only for a short time in order to exhale used air from the lungs and inhale fresh air. Then they plunge back into sea ​​depths.

Which marine mammals travel the longest distances?

The record holder in this "discipline" is the gray whale. This animal, which is 13-15 meters long and weighs up to 35 tons, swims from 10,000 to 20,000 kilometers across the Pacific Ocean every year. The whale migrates between areas where it feeds and breeds. Since they live an average of 40 to 50 years, one whale in its life overcomes a distance that roughly corresponds to the distance to the moon and back.

What mammal can dive the deepest?

Among all mammals, the sperm whale is able to dive deeper than anyone - up to 1200 meters. There were even individuals who, hunting for cuttlefish, fell to 3000 meters. Sperm whales, whose length is 18 meters and weighs 50 tons, can stay at a depth of up to two hours without rising to the surface for oxygen.

Water-dwelling mammals do not have a greater lung-to-body-size ratio than land-dwelling mammals, but they can submerge up to long time, holding their breath, because they have developed alternative mechanisms to increase the amount of inhaled oxygen. This article discusses some of these mechanisms.

Unlike their terrestrial diving counterparts, seals, sea lions and whales dive while holding their breath for practical reasons, such as to search for food or escape from predators. As with land-dwelling animals, these dives are accompanied by physiological changes that require some adaptation.

The extent of this adaptation is greater than even the most accomplished human freedivers. This increased adaptability provides a partial explanation for the depth and duration of dives performed by such mammals. For example, existing record in the "no limit" discipline, 163 meters is a relatively shallow depth compared to the depths to which the bottlenose descends. The use of tools that record the time and depth of the dive, as well as acoustic transceivers, made it possible to track the dive of these whales to a depth of up to 1450 meters. By comparison, northern sea ​​Elephant dives to a depth of 1500 meters, although it should be noted that diving to such depths is not the norm for these animals.

Perhaps the most effective physiological "equipment" is the New Zealand sea lion, a mammal that can make longer dives than any other species, typically descending to a depth of 120 meters (the deepest recorded depth was 474 meters) and easily remaining at that depth for five minutes. Although this depth and duration of diving is available to other marine mammals, these animals are distinguished from others by the manner of their diving, since they dive underwater almost continuously. Of interest to freedivers is the fact that almost half of the dives performed by this sea lion exceed its theoretical aerobic diving threshold (ATD, see below).

Calculating the aerobic diving threshold

In theory, if a freediver starts a dive with a total lung capacity (FLC), the maximum theoretical depth can be calculated as the ratio of LPO to residual lung capacity (RRC). Based on these calculations, it is possible to predict the maximum “theoretical depth” or “dive stop point” that Pipin Ferreras, a diver with a LPO of 9.6 liters and a RTL of 2.2 liters, can reach. By applying the Boyle-Mariotte law, it can be established that the safe compression threshold for Ferreras is about 4.4 atmospheres (at absolute pressure), which corresponds to a depth of 34 meters. Fortunately, freediving sportsmen pay little attention to the laws of physics, so Ferreras dived 128 meters below his theoretical maximum depth. Clearly there are diving mechanisms that allow freedivers and seals to circumvent these laws.

For freedivers who wish to calculate their theoretical depth threshold, there is the following formula (for practical use only).

Assessment of residual volume (RVR) of the lungs depending on age, height and body weight.

In freediving, ROL affects the depth that a freediver can reach without experiencing chest compression problems. Usually the ratio of LPO to OOL on the surface determines maximum depth a dive in which the athlete will not experience chest compression. One way to set your OOL is to perform the following calculations.

Equations for calculating ROL

Variables: age (years), height (cm), weight (kg).
Normal weight - men:
BV (L) = (0.022 x Age) + (0.0198 x Height) - (0.015 x Weight) - 1.54
Normal weight - women:
BV (l) \u003d (0.007 x Age) + (0.0268 x Height) - 3.42

Mechanisms by which "animal divers" resolve the tension between energy demand during a dive and conservation limited stocks oxygen levels are similar to those encountered by land-based freedivers and are not fully understood. However, there are definitely some physiological advantages at the disposal of our marine brethren.

For example, a seal's maximum submersion time is not determined solely by its ability to conserve oxygen, since seals can operate anaerobically. However, aerobic metabolism is preferable to anaerobic because it is much more efficient. Reducing the metabolic rate allows the seals to increase the amount of time they maintain aerobic respiration during a dive, as this allows them to use their oxygen stores more economically. In addition, through selective tissue perfusion, seals are able to increase the duration of oxygen storage. The point at which a seal or other diving animal needs to come up and breathe in oxygen or switch to anaerobic respiration is called APN. The level of lactic acid salts in the blood begins to rise above the values ​​of the resting state after reaching the APN and leads to a burning sensation in the muscles.

So how do seals operate anaerobically? Unlike human tissues, seal tissues are much more tolerant of the three factors of asphyxia: lack of oxygen, high levels of carbon dioxide, and low level pH. The lack of oxygen is caused by its consumption during aerobic respiration, carbon dioxide is a waste product of the muscles, and low pH is the result of the release of lactic acid during anaerobic respiration. The ability to easily tolerate these three factors allows the seal to operate in an anaerobic mode after the exhaustion of oxygen reserves.

Long dives usually force seals to exceed their APN and resort to anaerobic respiration. This was experimentally established by blood sampling: an increase in the level of lactic acid salts in the blood indicated that the seal used anaerobic respiration. Seals use different ways diving to get rid of the residual lactic acid that builds up during anaerobic diving. For example, the recovery time after diving in Weddell seals varies depending on the length of time spent underwater. After several long (about 20 minutes each) dives, these seals perform a series of short aerobic dives, which gradually remove accumulated lactic acid salts from the blood.

Another strategy used by seals, sea lions and whales to store oxygen is to achieve energy efficiency. As can be expected, the depth of the dive and, consequently, the distance travelled, affect the amount of time left for smooth gliding, which is the main method of storing oxygen used by marine mammals. The amount of time spent sliding smoothly during a dive increases significantly and non-linearly with the depth of the dive and translates into significant energy savings in terms of oxygen use.

Another mechanism used by seals is the way they store oxygen. Seals do not use their lungs to store oxygen. As can be seen from the graph, during the dive, the seal's lungs contain significantly less oxygen than the human lungs. When diving, the seal cannot store oxygen in the lungs due to the serious risk of decompression sickness upon ascent.

Graph: Location of oxygen reserves

Purple is a seal, lilac is a person.

So how does a seal store oxygen? The answer is in the blood and tissues.

Seal blood has a better oxygen-carrying capacity than human blood, partly due to the greater volume of blood in seals and partly due to a higher hematocrit (hemoglobin concentration). Since the seal has more blood in its body, it also has more red blood cells (erythrocytes). More red blood cells result in higher levels of hemoglobin, the pigment in red blood cells that carries oxygen. However, seal erythrocytes have a lower water content than erythrocytes. land mammals, therefore, even at the cellular level, this animal is designed to store more oxygen - this explains its higher hematocrit. Of course, the number of red blood cells in the blood is limited, because, as we know, if there are too many, then the blood becomes too thick for the heart to work properly. However, marine mammals get around this limitation by resorting to additional methods of storing oxygen for later use.

One such way is to use myoglobin, which is a compound found in muscles that binds oxygen. In fact, myoglobin is so highly concentrated in seal muscles that it is almost black under a microscope! Humans also have myoglobin, but unfortunately for freedivers, its oxygen storage capacity is much less than that of seals.

Species / Myoglobin (g/100 g)
Northern fur seal - 3.5
sperm whale - 5.0
Weddell seal - 5.4
Striped seal - 8.1

Among other things, marine mammals are able to store oxygen in body tissues that humans cannot, which gives them the ability to store more oxygen. This is especially true for the spleen. The mechanism for storing oxygen in the spleen is similar to that used by humans, however, the oxygen capacity of the spleen marine mammals much more than in humans.

Chapter seven. Deep sea diving

Living in aquatic environment creates a number of difficulties for animals breathing air. Their breathing is limited by external conditions and demands that land animals do not know. Although dolphins are everywhere, although they are tamed, almost nothing is known about the nature of their respiratory function. But it must be managed in a special way, otherwise their life in the water would be impossible.

Laurence Irving, 1941

How extremely mobile deep-sea squids get into the mouth of a sperm whale - whether it lures them or pursues them - we do not know. But we are well aware that the sperm whale is looking for them at a depth of up to 1.2 km, and even deeper, and it can stay there for much more than an hour. For a mammal that is descended from land animals and breathes air, such a way of life is extremely difficult.

Some of the relatives of the sperm whale, representatives of the family of beaked whales, although they are smaller in size, are in no way inferior to their giant relative in the art of diving to depth. Small cetaceans, we believe, do not reach such depths, but there is evidence that common dolphin, well known for its habit of "riding" the wave diverging from the bow of the ship, at night hunts for fish and cephalopods at a depth of 240 m, and this is also not a little.

Seals and sea lions have retained their connection to the land and are therefore less adapted to the aquatic lifestyle than dolphins and whales. But some of the pinnipeds are divers anywhere! It is known that the Antarctic Weddell seal can dive to a depth of 610 m. One seal spent 43 minutes underwater, reaching a depth of 200 m.

For a warm-blooded animal breathing atmospheric air, the ability to stay in a world of cold, darkness and overwhelming pressure for such a long time is a remarkable achievement. So how does it manage the amount of oxygen that it carries in the lungs, which, at first glance, should not be enough to make deep dives? How does it resist not only the direct physical impact of pressure, but also the consequences of the rapidly changing processes of compression and decompression of the body?

Man is surprisingly well adapted for diving, although for him, a terrestrial animal, the underwater world is a much more alien and formidable element than for him. younger brothers, long ago settled in the water kingdom. Perhaps we can better appreciate the problems that marine mammals have to deal with when diving to great depths, if we enumerate the dangers for a person to stay too long at excessive depths.

For at least 6000-7000 years, man has been raiding the bottom of the sea, extracting pearls, expensive corals, sponges and various types of edible animals. chief actor of these raids was a naked diver, he reached the bottom with the help of a stone, and the area of ​​\u200b\u200bhis invasion was limited coastal zone with 30 meters depth. Even the Lucayan Indians, pearl divers in the Caribbean who were famous for being excellent divers at great depths, most likely did not descend (although they are said to be able to hold their breath for 15 minutes). The famous Japanese "ama" - female divers, have been working for over 2000 years at depths from 15 to 24 m. With age, they lose their hearing and their predisposition to lung diseases increases.

Island pearl divers Pacific Ocean descend deeper - up to 42-45 m, but some of them pay for it, falling ill with a strange illness - "taravana", which means "falling in a fit of madness". AT different places attacks of taravana proceed in different ways. They are accompanied by dizziness and vomiting, ending in partial or complete paralysis, and there are cases of death. Taravana is somehow connected with the mode of breathing. It is not known to the divers of Mangare-wa Island, who rest between dives for 12-15 minutes, and the pearl seekers of the Paumotu Islands, diving to the same depths, but hyperventilating their lungs with frequent and deep breaths for 3-10 minutes between dives, suffer from tarawana.

The deepest divers in the world are apparently the Greek sponge hunters. They reach depths of about 56 m. (It is said that one, now legendary, diver in 1906 took out a lost anchor from a depth of 60 m *.) but surveys carried out even today have shown that their current descendants are the least affected by physiological disorders of all other professional divers. On this basis, even the conclusion is drawn that for more than a hundred generations, hereditary divers could have developed and consolidated immunity to the effects of deep-sea diving. Like it or not, it's hard to say. But when sponge hunters got their hands on the soft helmeted diving suit invented in 1837 by August Siebe and stayed at depth longer than their ancestors, half of those who worked in the suit died within a year. It was only gradually, through trial and error over the years, that the Greeks were able to develop diving rules that determined the duration of stay under water, the safe speed of return to the surface and the permissible frequency of diving. The descendants of those "helmetheads" and now, by all accounts, can work the longest of their fellows in the profession on the seabed.

* (The depth record for a diver who does not use any underwater equipment is 73 m. It belongs to a crew rescue specialist from submarines Robert Croft. But this is a record, and not a working dive with some task at depth. Barely reaching the 73-meter mark, Croft immediately began to rise.- Approx. ed.)

But if, before the invention of the diving suit, the Greek sponge hunters enjoyed a reputation as peaceful and kind-hearted people, then, having started using the "helmet", they completely changed and turned into "a bunch of noisy drunkards. In the harbor, they only know that they get drunk in honor of the fact that returned alive, and are trying with the help of alcohol to gain courage for a new campaign" * .

* (The Japanese "ama" are described in detail in the book "Immersion Physiology and Japanese Ama" (Publication No. 1341 of the National Research Council of the National Academy of Sciences, Washington, 1965). The book includes a chapter on the pearl divers of the Tuamotu Islands by E. R. Cross. Much of the material on the Greek sponge hunters comes from an article by Peter Throckmorton in The Man Under the Sea, Chilton Books, 1965.)

From a purely theoretical standpoint, it is very difficult to imagine a diver going deeper than 30 m underwater. Already at this depth, as emphasized in a textbook for divers navy USA, a diver is subjected to a pressure of 4 atmospheres. His lungs, having a volume of about 6 liters on the surface, are compressed there to 1.5 liters, that is, almost to the so-called residual volume corresponding to a full exhalation. Further immersion may cause lung injury due to compression of the chest or pushing of the diaphragm into the chest cavity. At the same time, blood and lymph are squeezed out into the alveoli and bronchi, where there was residual air under less pressure. The native divers of the Pacific Islands are hardly aware of this, may this ignorance serve them well.

This external "contraction" is very dangerous, although resistance to it varies widely. But this is only one of the dangers that a soft-suited deep-sea diver faces. At high blood pressure in large quantities nitrogen begins to dissolve in the blood. And if a diver stays at depth for a long time, his blood and body tissues have time to be saturated with gas to the limit. When slowly rising to the surface, the dissolved gas has time to be released from the blood and tissues of the body through the lungs during normal breathing. But if the diver ascends quickly, the excess nitrogen will be released in the form of bubbles directly in the vessels and tissues of the body, as happens in a bottle of carbonated water when it is opened. These blisters cause excruciating pain and, in more acute cases, paralysis and death. Although sponge and pearl hunters encountered this decompression sickness in antiquity, it received its current common name "caisson sickness" in the 19th century, when it tragic consequences experienced by workers descending into the caissons, where, under increased pressure, bridge piers were installed and tunnels were dug under rivers. The only way to avoid decompression sickness is to gradually reduce the pressure so that the nitrogen dissolved in the blood is released without forming bubbles in the vessels and tissues of the body.

Many people believe that a diver who goes underwater without scuba gear or a soft suit with a helmet is not in danger of decompression sickness. He spends little time at the bottom, does not inhale compressed air, the remaining air in his lungs is squeezed out into the bronchi, from where gas does not enter the blood. All this is true when it comes to a single dive, but when a diver goes underwater several times in a row, an excess amount of nitrogen gradually accumulates in his blood. And at the end of a series of dives, a person should feel some signs of decompression sickness.

In fact, this is the case, and decompression sickness, under various names, is well known to professional divers, although they may not understand the essence of the phenomena that occur to them. As an example, I will cite a convincing experiment that a Danish Navy medical officer did on himself: having made several dives in a row to a depth of 20 m in a training pool, he felt the symptoms of decompression sickness * . There is only one way to avoid the accumulation of excess nitrogen in the blood: diving at long intervals, during which the normal concentration of nitrogen in the body is completely restored.

* (This experiment was carried out by the Danish officer P. Paulev. He reports his results in his article "Decompression sickness after several breath-hold dives," included in Publication No. 1341, referred to in the previous note.)

The tarawana of the pearl divers of the Paumotu Islands remains a mystery to us. Unlike bend sickness, it can manifest itself as a sudden and complete paralysis at a time when the diver is at a considerable depth. It is even more surprising that the victims of the tarawana do not feel pain. There is no doubt that tarawana is a form of decompression sickness, but we have not yet understood why it is so different from the usual form and what exactly causes it.

After the invention of scuba, the insidious effect of compressed nitrogen, called nitrogen poisoning, became widely known. However, in a narrow professional circle, this phenomenon has been known for 150 years. Divers wearing Ziebe's metal helmet were the first to experience nitrogen poisoning. Something strange began to happen to them. They began to feel an irresistible desire to catch fish with their hands, to embark on an intricate dance, and completely forgot about work. There were cases when a diver with his own hand cut the hoses supplying air to his helmet. For a very long time it was not possible to understand what was the matter here, and even now this phenomenon, which Captain Jacques-Yves Cousteau called the "call of the abyss", is far from being fully studied. But under this exciting name it has become known to millions of people, let this fame serve as a warning to careless and imprudent scuba divers.

Nitrogen poisoning awaits a scuba diver or a diver in a space suit with a helmet if he breathes atmospheric air at a depth of more than 30 m. Susceptibility to poisoning is individual character, so that some divers work calmly at a depth of 60 m, and some do not hear the "call of the abyss" even at a depth of 90 m. Only switching to breathing mixtures that do not contain nitrogen, such as helium-oxygen, can save a person from the dangers of nitrogen poisoning. It is now generally accepted that compressed nitrogen, dissolving in the blood, acts like alcohol or weak anesthetics and narcotic drugs. The higher the pressure, the stronger this effect is manifested, more and more reminiscent of the effect of "laughing gas" - nitrous oxide.

Simple divers who do not have either scuba gear or soft suits with helmets are apparently not in danger of nitrogen poisoning. At great depths, where there is a danger of such poisoning, they very rarely get there, they do not stay there for long, in addition, the supply of air in their blood and lungs is very limited. But it is possible that if one of them managed to hold his breath for a few minutes and dive to a depth of more than 60 m, as marine mammals do, such a daredevil would risk hearing the “call of the abyss”.

And, finally, about the last danger that awaits a diver on the seabed. The reserves of oxygen dissolved in his blood and body tissues are gradually depleted, and as soon as the concentration of carbon dioxide in the body reaches a certain value, the diver is at the mercy of the unconditioned exhalation-inhalation reflex. To save a person from this reflex can only be a passion for work or some kind of unexpected event, completely capturing his attention; only under these conditions does a person not feel anoxia - a lack of oxygen in the tissues of the body and does not feel irresistible desire repeat the breath.

So, anoxia due to a decrease in the oxygen concentration in the tissues of the body during a long stay at depth, "compression" of the body, decompression sickness in its various manifestations and nitrogen poisoning - this is a short list of the phenomena that, in our opinion, marine mammals must face, often committing deep diving. And since cetaceans and seals withstand long dives to considerable depths without any damage to themselves, it is clear that over millions of years of life in the water, these animals have developed some physiological and anatomical features that protect against all of these factors.

But cetaceans and pinnipeds are not the only divers in the animal kingdom. There are many diving birds, and there are semi-aquatic animals such as beavers, otters, water rats and hippopotamuses that spend a lot of time underwater. All of them dive shallow, but nevertheless their anatomy and physiology have undergone a number of changes that allow them to stay under water for a long time. And many important discoveries concerning the physiology of deep-diving animals have been made precisely through the study of small animals that are well known to you, often and for a long time at shallow depths.

The pioneer in the field of physiology of immersion in water is the French biologist Paul Baer. Baer was interested in a wide range of issues, and among them - the definition of differences between purely terrestrial and diving animals. About a hundred years ago Baer published an account of his experiments with ducks, beavers and muskrats. Comparing a duck, which spends part of its time under water, with a chicken, which is a purely terrestrial animal, Baer noted that when forcibly immersed in water, the duck calms down for several minutes, and the chicken immediately begins to fight furiously and dies faster than the duck. After discovering that the body of a duck contains about twice as much blood as a body of a chicken, Baer concluded that the duck stores twice as much oxygen as the chicken, and this explains the ability of ducks to stay under water for a long time. Proving his hypothesis, Baer did the following experiment: after releasing some of the blood from a duck, he equalized the blood volumes of duck and chicken and made sure that both birds die under water at the same time.

Later studies have shown that the difference in the duration of immersion of different animals significantly exceeds the difference in blood volumes. Consequently, the ability to stay under water for a long time depends not only on the volume of blood, but also on other features, both anatomical and physiological. In particular, it turned out that when an animal is immersed in water, the frequency of contractions of its heart muscle decreases. This slowing of the heart - bradycardia - leads to a decrease in the supply of oxygen to muscle tissues. Unlike the heart and brain, muscles can work anaerobically (that is, without oxygen consumption) for some time due to their own supply, which is restored as soon as the animal returns to the surface. And, finally, it was found that in diving animals the respiratory center is insensitive to an increase in the concentration of carbon dioxide in the blood. This leads, firstly, to a more complete use of oxygen reserves, and secondly, to inhibition of the exhalation-inhalation reflex.

The physiological mechanisms that regulate the activity of the organism under water, as a rule, begin to act from the moment of immersion (although, for example, it is enough for a duck to take a posture that precedes a dive). All of them belong to unconditioned reflexes and, according to the observations of Lawrence Irving (whom I quoted at the beginning of the chapter), are inherent not only in diving animals, although these mechanisms are much more developed in them. Bradycardia on immersion in water occurs, for example, in all terrestrial animals, and in some people it is noted even in cases where they simply immerse their face in water. Interestingly, in fish, bradycardia manifests itself in the reverse order - it occurs when the fish is taken out of the water *.

* (Paul Baer's experiments with ducks and small diving mammals are described in his book Lectures on the Comparative Physiology of Respiration, published in Paris in 1870. More recent work in this field can be read in the following reviews: Breath of Diving Mammals by Lawrence Irving (see Physiological Reviews, vol. 19, pp. 489-491, 1939); P. F. Scholander, Animals in the Aquatic Habitat: Diving Mammals and Birds (see Habitat Adaptation, published by the American Physiological Society, Washington, 1964); X. T. Andersen" Physiological adaptation in diving vertebrates" (see Physiological Reviews, vol. 46, pp. 212-243, 1966).)

Laboratory experiments with small animals have largely clarified the physiological phenomena that occur in the body during immersion, but we still do not understand everything, because we are deprived of the opportunity to directly study these animals in vivo. The physiological characteristics of cetaceans can only be guessed based on the results of studies on the decks of whaling ships. Calculations of the metabolic rate of cetaceans are largely approximate or based on assumptions. Even about how deep whales dive, there is no consensus. Some believe that whales dive very deep, while others, while pointing out that we do not know how deep a whale can dive, nevertheless take the liberty of asserting that there are no special physiological problems during prolonged diving.

An example of how contradictory opinions on this subject can be found in the discussion under the general heading "Do whales reach great depths?", which was raised in the English magazine Nature in 1935. The discussion was started by reader R. B. Gray. Gray claimed that a harpooned whale dived straight down and surfaced near the dive site. Therefore, Gray continued, the depth to which the animal dived can be judged by the length of the given harpoon line. An adult bowhead whale chooses in such cases from 1280 to 1460 m of tench, a bowhead whale that has not yet reached maturity - from 730 to 1100 m, and calves - half as much. An adult male bottlenose whale (species not specified) chooses 1300 m of tench, females and calves - half as much. Gray believed that these are the depths that the whales reach.

The well-known English cetologist Dr. F. D. Ommani disagreed with Gray's assertions. According to Ommani, the coincidence of the places of descent and ascent cannot indicate that the wounded whale is diving vertically, and, therefore, the length of the etched line does not mean anything. Moreover, Ommani pointed out, the animal's behavior under these conditions cannot be considered natural. In conclusion, Ommani opined that in normal conditions whales dive no deeper than 360 m. "It is incredible," he wrote, "that an animal could withstand more pressure."

Gray objected to Ommani. He quoted the words of the famous whaler William Scoresby Jr., who emphasized that the length of the harpoon line that the whaler keeps ready is determined precisely by the depth at the fishing site and only in very deep places the length of the selected line depends on the size and strength of the animal being caught. According to Gray, these words of Scoresby indicate that the wounded whale is making a vertical dive. Claiming that a wounded whale during a dive only reaches its usual depths, Gray argues as follows: “If a harpooned whale went deeper than nature allows it, it would receive serious internal injuries that would deprive it of strength and mobility, and between to which the same Scoresby writes: “Often a whale that emerged from a wound looked full of strength.” As an additional argument, Gray cited stories of cases when the whale makes such a deep vertical dive that the line breaks, but the whale does not die at all, crushed by excessive pressure. , but goes free and can even recover from a wound: animals fell into the hands of the whalers, in the bodies of which the hunters found old harpoons * .

* (See Nature, Volume 135, pp. 34-35, 429-430 and 656-657, 1935.)

I don't know if these arguments convinced Dr. Ommani. I think the controversy has been going on for some time.

A great contribution to the study of diving birds and mammals was made by the Norwegian scientist Per F. Scholander. His first work on the subject, published in 1940, is still unique in its depth and breadth of coverage. Since the works of Scholander have helped us in many ways in our research, I consider it necessary to briefly describe the results achieved by the Norwegian scientist. According to data received from whalers, and according to our own observations of the duration of the dive of whales of the most different types Sholander found that the bottlenose whale (2 hours) and sperm whale (about an hour) are able to stay under water for the longest time. He noted that before diving, the whale takes several rapid strong breaths, accompanied by fountains of steam from the blowhole. Having surfaced, the whale rests the longer, the longer the dive was, and again starts up fountains. After examining the muscle tissue of the bottlenose whale and the sperm whale, Scholander found that they contain a very large amount of oxygen - almost half of the total oxygen supply in the body. Thus, Scholander partly confirmed the previously stated conjecture that during the period of being under water, the supply of oxygen to muscle tissues is sharply reduced, and the so-called retia mirabilis ("wonderful network"), a special system of blood vessels developed in cetaceans, supplies blood to the bypassing the muscles, supplying only the heart and brain with oxygen.

Scholander began his investigation of the question of whether marine mammals suffer from decompression sickness by directly measuring the depths that animals reach. As already mentioned, at that time these depths were estimated only presumably, and the estimates of different scientists differed greatly from each other. Ommani, for example, called the figure 40 m, other scientists - 90 m. It was known that the sperm whale got entangled in the cable at a depth of 275 m. 502 m.

The ingenious Scholander constructed a simple depth gauge by filling a glass capillary tube with colored water and sealing it at one end. After the water dried, a deposited layer of paint remained on the inner walls of the tube. When immersed in water, the tube was partially filled from the open end, the paint on the walls of the filled part was dissolved and washed off, and by the ratio of the lengths of the painted and unpainted parts of the tube, it was possible to calculate at what depth the device had been. The tubes, calibrated in the laboratory, were fastened with a light harness to the bodies of a common havoc and several seals. A fishing line 180 m long with a float at the end was tied to the harness. The animal was allowed to dive free several times, and then it was caught again and the equipment was removed. The greatest diving depth of the common harbor porpoise was 20 m, and the six-month-old gray seal reached the 76-meter mark during the first dive.

Scholander repeated these measurements while hunting fin whales, attaching tubes to harpoons and agreeing with the whalers that they should not restrict the movements of wounded animals by pulling the harpoon line (which they usually do). Almost all harpooned animals dived and were still alive when they returned to the surface. Fin whale diving on the nai great depth- 365 m, then dragged a whaling ship behind him for half an hour before he was finished off. But one slightly wounded whale, which went to a depth of 230 m, surfaced, lay on its side, released several fountains and died. Whalers claimed that such cases happened more than once. It was impossible to say with all certainty that this fin whale died from decompression sickness, but Scholander considered this reason to be quite probable. As to whether a sperm whale entangled in a cable and a fin whale that had broken its vertebrae would have experienced decompression sickness had they returned alive to the surface (which was discussed earlier), Scholander could not say anything.

Having gained an idea of ​​the depths that cetaceans and pinnipeds of different species reach, Scholander made a comparative study of their lungs and found that the greater the depth of a given species of animal, the smaller the volume of their lungs in relation to body size. Therefore, Scholander reasoned, the deeper an animal dives, the less oxygen it carries in its lungs. The pattern found was confirmed by the observation that seals exhale before diving, or at the very initial stage of diving. This means that the diving animal protects itself from excessive dissolution of gases in the blood under pressure by taking the minimum amount of air with it. This is what saves the animal from decompression sickness during a quick return to the surface. In addition, during a deep dive, the lungs are compressed to a residual volume and air is squeezed out of them into thick-walled cartilaginous bronchi, where there is practically no gas exchange with blood. From all this it followed that the greatest danger from the point of view of decompression damage is not a deep-sea dive with a quick return to the surface, but a long stay at a relatively shallow depth, where the lungs do not shrink to a residual volume under water pressure. - that the sperm whale and the bottlenose whale, diving, strive to cover the first two hundred meters as quickly as possible precisely in order to avoid the danger of a decompression defeat three times back" * .

* (The work of P. F. Scholander " Experimental studies respiratory function of diving mammals and birds" appeared in 1940 in Norwegian (see Hvalradets Skrifter, no. 22, Oslo).)

All doubts about how deep sperm whales can reach of their own free will disappeared in 1957 after the publication of a report on 14 cases when sperm whales became entangled in submarine cables. In six cases, the cables lay at depths from 900 to 1100 m. The number of these cases is too large to admit that a sinking, agonizing animal was entangled in the cable, although it is not clear exactly how these unfortunate incidents occur. So far, only one more or less plausible explanation has been proposed: the sperm whale, pursuing prey at the very bottom, rapidly rushes forward with its mouth wide open, lower jaw set aside at a large angle; from the whole course, catching the cable with its lower jaw, it somersaults (this happens with dolphins that fall into the net) and at the same time can be hopelessly entangled *.

* (See B. S. Khizn's article "On Whales Entangled in Deep Sea Cables" in Deep Sea Research, Volume 4, pp. 105-115, 1957.)

At the beginning of the chapter, I mentioned that the Weddell seal can hold its breath for 43 minutes and dive to 600 m. The lifestyle and immediate habitat of this animal prompted scientists to take a closer look at the Weddell seal, a large agile animal that weighs up to 450 kg. Living in Antarctic waters, he often finds himself in situations where a whole group of animals has to breathe through a single hole in the ice. Dr. J. L. Coyman used this feature to record the depth and duration of dives of the Weddell seal. Appropriate sensors were attached to adult seals and the animals were released into a single outlet within a radius of 1.5 km. The seals could return only to the same vent, where all the devices were removed from them. Koyman managed to obtain data not only on the depth and total duration of the dive, but also on the rate of descent and ascent. It turned out that when diving to a depth of 300 m or more, the seals descend and return at a faster rate than during shallow dives. Of course, they could do this, wanting to stay longer at depth, but one should not forget about Scholander's conclusions. Perhaps, diving to great depths, the Weddell seal instinctively strives to quickly pass the danger zone, staying in which threatens him with decompression sickness. And it is quite possible that he slowly returns to the surface after shallow dives for exactly the same reason that a diver who has completed a long work on the seabed is in no hurry to return to the top.

* (For further details on the work of J. L. Coyman, see his article "An Analysis of the Diving Behavior and Physiology of the Weddell Seal" in Biology of the Antarctic Seas (American Geophysical Union Publication No. 1579, 1967).)

By the time our work began, that is, by 1960, the general picture of the interaction of various biological mechanisms, triggered during deep diving, was very incomplete, and in some ways contradictory.

Sam Houston Ridgway, the first veterinarian of our pets, became very interested in all these questions. We met him when he was an officer at Oxnard Air Force Base, next door to us. There were no veterinarians in the naval units, and when our dolphins fell ill, we naturally turned to the office of Captain Ridgway for help, especially since in this case we were not hindered by the question of the cost of treatment. After completing his military service, Ridgway joined us at the station as a civilian, and he was entrusted with the care of the health of animals.

Sam is a man of inexhaustible energy, all-encompassing curiosity, inventive mind and tenacious grip. He spent whole days at the station, usually stopping by on weekends to check on the condition of the animals and, if necessary, prescribe a course of treatment, and devoted his evenings to writing reports. In three years he achieved international fame as a specialist in the treatment of marine mammals, and two more years was enough for him to become a famous physiologist.

Sam's first work was devoted to comparing the characteristics of the blood of three various kinds dolphins. These were: the white-winged porpoise, discussed in Chapter 3, the Atlantic bottlenose dolphin, which lives in shallow coastal waters (it can reach speeds of up to 37 km / h, but has never been considered the fastest swimmer among cetaceans), and the Pacific white-sided dolphin, or leg, - an animal that lives on the high seas, like "white-winged porpoise, inferior to it in swimming speed and, probably, in diving depth. In other words, in some respects, legs could be considered intermediate between bottle-nosed dolphins and white-winged sea ​​pig.

An important part of the work was to determine the ability of the blood to store oxygen. The supply of oxygen in the body depends on the concentration of red blood cells and the total volume of blood. Before that, no one had tried to measure the total amount of blood in a live cetacean. By making such measurements on other animals, the researcher simply measured the amount of blood that flowed from the dying animal, while getting underestimated and inaccurate results.

Sam used a recently developed harmless method based on the introduction of a small dose (radioactive iodine) into the blood of a living organism. 10 minutes after the injection (it is assumed that during this time the blood will completely circulate and the iodine will be evenly distributed in it), a small sample of blood is taken from the animal and its radioactivity is determined.The degree of iodine concentration determines the total volume of blood.The number of red blood cells is measured by a standard laboratory method.

The results for all three species were strikingly dissimilar. The ratio of the amount of blood to the body weight of the white-winged porpoise was twice that of the Atlantic bottlenose dolphin. Legs took place exactly in the middle. Even greater differences were found in the ability of the blood to be saturated with oxygen. In the white-winged porpoise, this ability was three times greater than in the bottlenose dolphin. The relative weight of the heart in the white-winged porpoise turned out to be 1.4 times greater than in the Atlantic bottlenose dolphin (measurements were made on animals that died for one reason or another). The data obtained agreed very well with what was or was believed to be known about the ecology and behavior of animals of all three species. This explains why white-winged porpoises can swim faster and dive deeper than bottlenose dolphins *.

* (See S. H. Ridgway and D. J. Johnston, "Blood Oxygen Capacity and Ecology of the Three Genera of Dolphins," Science, vol. 151, pp. 456-458, 1966.)

As noted earlier, in the early studies of the physiology of diving, animals were forcibly submerged in water. It is difficult to expect a dolphin or seal tied to a board and lowered under the water against their will to behave in exactly the same way as if they were diving of their own free will. Moreover, during such experiments, animals happened to die, although they were not forced to do anything that would go beyond their capabilities.

Successfully teaching dolphins to dive on the high seas allowed Sam Ridgway to conduct a unique experience with Tuffy. First, Sam decided to find out how deep Tuffy could dive. And secondly, he decided to analyze the composition of the air exhaled by Tuffy in three different situations: a) immediately after ascent from great depth, b) after holding air in the lungs for a time equal to the time of deep-sea diving (provided that the dolphin does not leave the surface) and c) after the dolphin has covered the distance from one diver to another at a depth of 20 m (that is, at a shallow depth) in a time equal to the time of deep-sea diving. At the end of each experiment, Tuffy had to dive under an inverted funnel and exhale air into it, after which the air samples taken were delivered to the laboratory. As you can see, the dolphin had to work and very thoroughly.

By this time, Tuffy was already diving deeper than 180 m. He learned to swim underwater from one diver to another by calling a buzzer or other acoustic device. Chief Bill Skrons had to teach the dolphin, on command, to hold his breath for a certain period in the "lying on the surface" position, and then work out the final spectacular trick - exhaling under an inverted funnel. Dolphin perfectly understood what they wanted from him, and, according to Skrons, he mastered new system exhale for 10 minutes.

Taffy's place of work was 8 km from the station. Usually he "saddle" the wave, diverging from under the propeller of the boat Skrons, and most of the way he "ride a hare". Arriving at the place, Skrons lowered the training device to the prescribed depth, turned on the buzzer, Tuffy dived, pushed the rod with his nose, the sound turned off, the dolphin returned without floating up, exhaled air under the funnel, and then jumped to the surface for a reward and fresh air.

From the behavior of the dolphin and its echolocation clicks, it was clear that Tuffy had been continuously monitoring its location since the device was immersed in water. It is possible that the dolphin could judge the depth at which the device hovered by the intensity of the signal coming to the surface. Be that as it may, the dolphin always knew to what depth he was to dive, and before diving to 150-180 m, he hyperventilated his lungs, making 3-4 quick breaths. Since he was hyperventilating even when such a deep dive was the first dive of the day, it can be argued that he really knew where he was going to be sent and his behavior was not related to the expended energy during the previous dive. When the dolphin had to hold air in its lungs while remaining on the surface, it did not hyperventilate because it could not know in advance how long it would be told not to breathe.

In total, Tuffy made 370 deep-sea dives. The total length of the cable, to the end of which the control device was suspended, was 300 m, the dolphin reached this depth and returned back in 3 minutes 45 seconds. During one lesson - 60 minutes - he dived 9 times to a depth of 200-300 m at intervals of 3-5 minutes. Staying on the surface, Tuffy kept air in the Lungs for an average of 4 minutes. The record delay time was 4 minutes 45 seconds*.

* (Peg, who took a similar course of study, could hold her breath even for 6 minutes. - Approx. ed.)

Laboratory analyzes of the gas mixture exhaled by Tuffy fully confirmed Scholander's hypothesis. They showed that the largest number Oxygen Tuffy consumes during flights from one diver to another at shallow depths. The mixture exhaled by the dolphin after this exercise contained only 2% of the normal oxygen content in normal atmospheric air- the level at which a person would have lost consciousness long ago. Lying on the surface and not breathing, Tuffy consumed less oxygen from the supply available in his body. But the dolphin spent the least amount of oxygen during a deep-sea dive. The maximum concentration of carbon dioxide in the exhaled mixture was observed after holding the breath on the surface, and the minimum - after deep-sea diving, although it required a much greater effort from the animal.

The data obtained allow us to state that when diving deeper than 90 m, the oxygen stored in the lungs by the dolphin diffuses into the blood very slowly. Probably the same thing happens with nitrogen. So Scholander is right: Tuffy was threatened with decompression failure not during a rapid ascent from a great depth, but after a long stay at a relatively shallow depth.

Divers observed the effect of pressure on Tuffy's chest even at a depth of 20 meters. To see what a dolphin looks like at a depth of 300 m, Sam fitted an underwater camera to the control device, and Taffy took a picture of himself at the moment when he turned off the buzzer. The picture clearly shows that the dolphin's chest has the ability to significantly decrease in volume without any harm to the animal.

As is often the case, the experiments performed did not so much answer questions as raised new ones. It is not clear how Tuffy could have been active at such a low level of oxygen supply that Sam registered. According to Ridgway's calculations, the stored oxygen barely had to be enough to maintain cardiac activity. But how did the brain cope, the action of which in an oxygen-free regime is impossible to imagine? Nevertheless, there were no signs of oxygen deficiency in Taffy's behavior *.

* (The experiments with Tuffy are described in the article "Breathing and Deep Diving of the Bottlenose Dolphin" by C. H. Ridgway, B. L. Scrons, and John Canwisher (Science, vol. 166, pp. 1651-1654, 1969).)

We have been able to teach sea ​​lion dive on command to a depth of 230 m, and a grind to a depth of 500. As in the case of Tuffy, we cannot say that this is the limit for them. Moreover, we witnessed how the pilot whale, on its own initiative, dived to 610 m.

Thus, the work of our specialists has replenished the stock of knowledge about how deep marine mammals can dive and how long they can stay under water. And now we have the right to say that trained cetaceans and pinnipeds can deliver scientific information to humans from 500-meter depths in the open sea. Moreover, information that cannot be obtained by any of the methods known to us.