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Rest, a state of reduced metabolic activity adopted by many organisms under conditions of environmental stress or, often as in, when such conditions may occur. There are several conditions in which organisms are not stressed. Some animals migrate long distances to avoid adverse situations; others reduce environmental stresses by changing their behavior and the habitats they occupy. For example, arctic lemmings may avoid harsh winter weather, limiting his life in winter to active actions under the snow cover.
Anatomy, morphology and ecology of reptiles
12. annual cycle reptile life
In reptiles, it is expressed in the alternation active period during the warm season and torpor (hibernation) during unfavorable periods (winter in temperate latitudes, summer drought in arid regions). Reproduction, growth and resettlement of young animals, the accumulation of fat reserves necessary for experiencing the period of stupor are timed to the first period. Annual biological cycles are clearly expressed in the inhabitants temperate latitudes, weaker in the subtropics and less noticeable in tropical regions. However, even there, while maintaining activity throughout the year, in each species, the breeding season is replaced by a time of sexual dormancy. Only some tropical and subtropical lizards can repeat oviposition in different months.
Another one used by some organisms to prevent stressful environmental conditions is the resting state, during which the organism maintains the amount available to it and makes few demands on the environment. Most of the major groups of animals and plants have representatives that can become dormant. Resting periods vary in length and degree of metabolic decline, ranging from only marginally less metabolism during intermittent short rest periods of deep sleep to more extreme contractions over longer periods of time.
Biological cycles can differ significantly not only in different types but also in individual populations of the same species. Green turtles - Chelonia mydas in the Caribbean Sea lay their eggs in May-October, on about. Ascension - in January-April, and in Ceylon - in July-November.
Timing of reproduction(oviposition and release of young from eggs) depend on local conditions and fall on optimal periods - favorable weather and good food opportunities. So, Central Asian tortoises - Testudo horsfieldi in Central Asia, leaving their wintering shelters in early spring, immediately start breeding and in May-June, even before the summer drought, the female manages to lay three clutches of 2-6 eggs each. Turtles hatch from them in August-October, which remain to winter in the ground and come to the surface only in the spring of next year. In the tropical regions of the Amazon and Orinoco, the river tartaruga shield-footed turtle - Podocnemis expansa breeds in the middle of the dry season. Round-headed lizards in Central Asia begin mating in autumn and some of the females go into wintering fertilized; mating resumes the following spring.
Amphibians and reptiles
From an evolutionary perspective, dormancy appears to have evolved independently of a wide range of living beings, and dormancy mechanisms vary depending on the morphological and physiological makeup of each organism. For many plants and animals, generation has become integral, allowing an organism to progress through critical ecological stages in its life cycle with minimal impact on the organism. When lakes, ponds or rivers dry up, for example, aquatic organisms that may enter a dormant period survive while others die.
Active period duration depends on temperature conditions, rainfall, availability of available food and the ability to endure adverse conditions. So, the common viper, Vipera berus, which penetrates far to the north, falls into a stupor later than other reptiles, and becomes active earlier in the spring. The viviparous lizard - Lacerta vivipara - is active in Southern Europe for about 9 months a year, in central Russia - about 5.5 months, and even less in the north. The duration of stupor in unfavorable periods is just as different. AT warm winters in the Caucasus and in the republics of Central Asia, some snakes and lizards (spinning muzzle, gyurza, efa, foot-and-mouth disease, roundheads) come out of winter shelters on warm days. Living in warm buildings, agamas and geckos in Central Asia do not fall into a stupor at all. In the same places, Central Asian turtles, whose food (juicy green vegetation) in deserts and semi-deserts often dries up already at the end of May, are active only in spring and early summer, sometimes no more than three months: before a summer drought, they fall into a stupor and wake up only the next in the spring - their summer hibernation turns into winter.
In addition, animals that can become dormant during the extreme cold of winter may expand their ranges in areas where animals unable to rest cannot live. The dormancy also ensures that these animals are free from competition during their periods of activity. Thus, dormancy is an adaptive mechanism that allows the body to satisfy environmental stresses and exploit ecological niches that would otherwise be untenable at certain times.
The inactive state that is induced in the body during periods of environmental stress can be caused by a number of variables. In general, since organisms generally exist within a relatively narrow temperature range, temperatures above or below the limits of this range may induce dormancy in some organisms. Changes in temperature also affect other environmental parameters such as the availability of food, water, and oxygen, thus providing additional incentives for rest. For example, in arctic regions, some animals become dormant during the winter months when food is less abundant.
hibernate reptiles in shelters - natural shelters, rodent burrows, own burrows (rarely). Many species of lizards and snakes hibernate alone, some - groups sometimes tens and hundreds. For example,
Cold blood does not warm.
Whoever is not allowed to maintain body temperature, in winter there is only one thing left - to freeze, fall asleep, become numb in order to wait out adverse living conditions. All cold-blooded animals do this: mollusks, crustaceans, spiders, insects, fish, amphibians and reptiles. With the onset of winter, they fall into hibernation, called cold stupor. The most they can do is to take care of a shelter where the temperature would not fall below 0 °C. otherwise, tissue cells are irreversibly injured by ice crystals formed during freezing. Crayfish, completely unaware of what a violent reaction in people causes their peaceful winter rookeries, burrow into the silt at the bottom of the reservoirs. Males usually hibernate in groups in deep pits at the bottom, while females singly in burrows. True, this cannot be called loneliness, because females glue from 50 to 500 pieces of fertilized eggs to their short legs, from which crustaceans the size of an ant hatch in early summer. If the silt freezes, the crayfish do not die and come to life when thawed. They are not afraid of a long stay without water, gradually replacing it in their gills with air with a characteristic sound (that is why they say that crayfish taken out of the water whisper, as if saying goodbye to each other). In the same place, pond snails spend the winter in the silt. Land snails, after accumulating the necessary nutrients, dig burrows, where several winterers could “take a nap” together deep underground at a temperature of 7–8 ° C. Having clogged the shelter well, they descend to the bottom and lie down with the opening of the shell upwards, which, however, is also tightened with a mucous substance. With a significant cold snap, the snails burrow even deeper, forming new films and air chambers that play the role of an excellent insulator. All metabolic processes abruptly, within a month, fade in order to reach the minimum at which the animal falls almost into a state of suspended animation with barely perceptible vital functions. and so from October to early April.
Cold blood does not warm
In desert biomes, on the other hand, the summer months, which can be periods of reduced food availability, intense heat, or extreme dryness, stimulate some desert organisms to become dormant. Lack of water during summer periods of drought or winter periods freezing, and annual changes in light duration and intensity, especially at high latitudes, are other environmental factors that can induce dormant states. Under natural conditions, most of the environmental variables that affect dormancy are interrelated in a cyclic pattern that is either circadian or annual.
The onset of the winter season catches insects at different stages of their development: in the form of eggs, larvae, pupae, or already adults. Each species has developed its own approach - at what stage is it better to “sleep off”. For example, ladybug and the malarial mosquito hibernate only as an adult, and aphids in eggshells. But there are those for whom any form of hibernation is good. Here are at least house flies - they hibernate both in the form of larvae, and in the form of pupae (in warm dung heaps), and in adulthood. The duration of sleep is also different: the peacock butterfly stays in a state of suspended animation for five and a half months at a temperature of about 6 ° C, and the silkworm needs a month more at 8.6 ° C.
Fluctuations in the main daily variables - light and temperature - can cause rhythmic changes in the body's metabolic activity; annual fluctuations in temperature and photoperiod can affect the availability of food and water. Oxygen and carbon dioxide concentrations do not typically change on a cyclical basis, but as a result of habitat selection, such as burrowing in mud, seeking dens, or other similar activities in which the body's metabolic reactions can change oxygen and carbon dioxide concentrations in the environment.
Even with the appearance of the first signs of a cold snap, insects find comfortable shelters under stones, tree bark, fallen leaves, in the soil, where a moderately low and uniform temperature remains after a snowfall. At 0 °C, their metabolism is greatly slowed down: respiration is suppressed, the rate of oxidative processes decreases by 10–15 times. To survive this, wintering is preceded by a certain preparation: fat reserves are accumulated (they reach 18% of body weight), the body is dehydrated as much as possible (in the larva of the gall midge, the water content drops from 65 to 20%). Some types of insects can tolerate very low temperatures, such as caterpillars of the meadow moth, which retain the spark of life down to minus 30 °C! But this is rather an exception, and not everyone can do this. Bees, for example, do not fall into long hibernation, the stock of accumulated fat does not exceed 1.5-2%. But still, at a temperature of 0 to 6 ° C, they become numb and can stay in this state for 7-8 days. At lower temperatures they die. Unfortunately for many lower animals, nature has not provided them with a tracking mechanism, and with an unsuccessful choice of a wintering place, stupor often turns into its logical continuation.
Trees of the world: fact or fiction? In an attempt to determine the relative influence of environmental factors on rest, they were experimentally modified. Research shows that an organism, once it has adapted to a sequence of cyclical rhythms, tends to maintain its adaptive behavior even if the environmental stimulus that originally caused the behavior is no longer present. For example, the Arctic terrestrial squirrel, when brought into the lab, provided with sufficient food and water, and exposed to constant temperature and light, has a periodic, innate behavioral pattern that operates independently of environmental cues.
Oddities of black fish.
Some species of fish react in a peculiar way to a sudden drop in water temperature - they fall into a state of shock. After a brief phase of arousal, they stop breathing, swim, and look dead. It is enough, however, that the water warms up, and they quickly come to life. Cooling turned out to be detrimental to fish, leading to the formation of ice crystals in the blood and tissues, damaging the walls of blood vessels. They can return to life only if the freezing extended only to superficial tissues. At the same time, the fish lives for some time due to the oxygen reserves in the swim bladder (the assumption that frozen fish breathe with gills turned out to be untenable).
Dormancy in protozoa and invertebrates
Other animals will often react as if they were subjected to cyclic changes in their home environment after they were removed from their natural habitats. 
Many parasitic and free-living protozoa exhibit a dormant stage by shedding a protective shell. The stimulus for formation in free-living protozoa may be a change in temperature, pollution, or a lack of food or water. the protozoan, which causes avoidance of environmental extremes, has two kinds of cysts.
One of the most cold-adapted fish - the so-called black fish - lives in the rivers, lakes and peat bogs of Chukotka and Alaska. The harsh climate allows her to revive only for a short time. summer period which she uses for reproduction. During the rest of the year, the fish burrow and freeze into the silt. If the temperature of the fluids in the body does not fall below -0.3 °C, then when they are slowly defrosted, they come to life. If the blood freezes, the fish die. The local population uses this fish as dog food. It is said that if a dog swallows a frozen fish whole, then soon after that it defrosts in the stomach and begins to strongly irritate its walls. in such cases, the dog usually regurgitates the fish, and if it falls into the water, it immediately swims away imperturbably.
Apparently, one is formed only to avoid stressful conditions; the other is formed for the same reason, but also involves asexual reproduction, resulting in a cyst that can contain up to 32 daughter organisms that occur under the right environmental conditions.
Free living protozoa form cysts around themselves and avoid extreme environmental conditions, but cysts are part of the life cycle of parasitic protozoa. The causative agent is found in the intestines of infected individuals, in whom it forms cysts that pass out into the faeces. When food or water containing cysts enters another person, the amoeba is released from the cysts and infects the new host. Without enteral action, which allows the body to live in a dormant state in an unfavorable environment, amoebic dysentery could be much easier to control.
From freshwater fish, carp, ruff, perch, catfish and others fall into hibernation in November. When the water temperature drops below 8-10 °C, these fish move to the deeper parts of the reservoir, the so-called wintering pits, burrow in large groups in the silt and remain in a state of stupor throughout the winter. at this time, in carp, the heartbeat slows down instead of the normal 25–30 beats per minute to 2–3, and breathing to 3–4 breaths per minute. Sturgeon, sterlet and beluga have an interesting adaptation - when severe cold sets in, their body is enveloped in mucus, which protects them from the adverse effects of the environment, and they hibernate. Some species of herbivorous fish (grass carp, silver carp) also hibernate in groups, covered with a thick layer of mucus. Some marine fish also endure severe cold in a sleepy state. In autumn, herring approaches the coast of the Arctic Ocean in order to fall asleep at the bottom of some small bay. Even the Black Sea anchovy moves to the southern regions - the shores of Georgia and the neighboring coast of Asia Minor, at this time the fish is weakly active and does not eat food.
However, protected by the cyst wall, the inactive contents of the cyst may survive for several weeks. They are also resistant to certain chemicals. Dormant cysts form during the life cycles of invertebrate parasites such as. The cyst stage of this organism develops in the muscles of the fish; if the fish is eaten raw or undercooked, the intercepted chance is passed on to the new host. The specific stage that causes trichinosis is found in the muscle cells of pigs; it is also an invertebrate parasite in which the dormant stage is an integral part of the life cycle.
salamander from eternal ice.
Amphibians prepare for the winter in advance, accumulating reserves of nutrients in the summer. And in autumn, when the daytime temperature drops to 8-12 ° C, and the night temperature drops to 3-5 ° C, they go to the places of future wintering, sometimes overcoming several kilometers. One part of them hibernates under water, the other - on land. Lake, grass, nimble, long-legged frogs hibernate under water. They gather in groups of 10–20 pieces (sometimes up to 100) of different sex and age, and sometimes of different types, and burrow into silt or underwater depressions. With such a group wintering, the metabolic rate of frogs is almost 40% lower than that of wintering alone. During hibernation frogs breathe only through the skin, the pulse slows down, but still, although extremely slowly, amphibians grow and their germ cells mature. Moreover, their sleep is not deep, and under adverse conditions they can move to another place in the same reservoir. The main thing is that this happens on time, because the most significant danger for them lies in the lack of oxygen. During very severe winters, even the mass death of amphibians occurs, especially when the reservoirs in which they winter freeze to the very bottom. Therefore, they prefer fast-flowing rivers and streams, channels, canals and lakes with rivers flowing into them, that is, they choose water bodies rich in oxygen. during hibernation in amphibians, the diameter of the blood vessels in the skin through which they breathe sharply increases.
When undercooked pork is eaten, the cyst wall is dissolved by digestive juices, and the worm is able to make its way into the tissues of the new host. The cyst-like forms found in many other invertebrate groups are inactive stages that persist during environmental stress. All freshwater and some marine species survive in the cold or drought by forming an adult sponge in the body. These structures, which are surrounded by a resistant coating, are released when the sponge dies and disintegrates.
When conditions are right, the cell mass emerges from the coating and forms a new sponge. They are microscopic aquatic animals that produce winters with thick and resistant coatings similar to protozoan cysts; eggs can remain dormant for a long time. They can survive drought or freeze and can be dispersed by wind or carried by animals. Thus, the cyst serves not only for the survival of the egg in adverse conditions, but also for dispersal. Some freshwater bryozoans develop disc-shaped buds or buds surrounded by a hard, chitinous shell.
Green and gray toads, common tree frogs, spadefoots, yellow-bellied toads, and salamanders spend the winter on land. They winter in large groups at the foot of cliffs, in rock crevices and between tree roots, in burrows dug by other animals, under a thick layer of leaves and moss. Some species can even burrow into the ground.
Tritons of different species hibernate both on land and under water. The former usually settle under rotten stumps and trunks of fallen trees, and if they do not find such comfortable apartments, they are satisfied with cracks in the soil. Of particular interest are Siberian newts - salamanders that live on a vast territory from Kamchatka and Sakhalin to the Urals. It is the only tailed amphibian north of the Arctic Circle. Even at 0 °C, it can still move, and some individuals of the salamander endure cooling (naturally, in a state of torpor) down to -37 °C. Geologists and builders have found newts frozen into excavated ice blocks. It often happened that newts thawed and released into heated water came to life, ate the food offered to them - flies, spiders, aquarium fish. in 1956, a mining team in the Magadan region found a triton at a depth of 14 meters. When they returned to the tent and lit the stove, the frozen animal gradually thawed and began to stir. His life lasted as long as 12 hours. At the same time, they hurried to declare this event a big sensation: a fossil newt was allegedly found, which, having been in a state of suspended animation for two million years, came to life again. In fact, the newt turned out to be not a fossil, but a modern one. But the question of how long the life of frozen amphibians can be preserved has remained a matter of controversy. The Siberian salamander found another time in Chukotka in a piece of eternal ice was subjected to radioisotope research. Kyiv scientists came to the conclusion that its age is in the range from 75 to 105 years, while the control amphibians were many times younger.
Among them, basically, they remain inactive during the day, with a soft head and foot, brought out in a shell. During periods of drought or cold, they withdraw into their shells and secrete a membrane of mucus and lime that closes the opening of the shell and resists drying out. on the other hand, they break out into the ground and secrete a mucous membrane around them for protection during periods of adverse environmental conditions. Among many freshwater forms, dormant cyst-like stages develop that resist desiccation and allow the species to survive adverse periods.
Almost all types of reptiles of the northern latitudes hibernate in winter. in the northernmost regions, it lasts 7–8 months. Further south, their hibernation is shorter. Lizards burrow into the soil, arranging holes for themselves on steep, dry slopes that are not threatened by flooding. on a nice sunny day, they wake up for a few hours to bask in the sun and hunt, and hide again, falling into a stupor. Land turtles climb half a meter deep into the soil, into natural shelters or holes of moles, foxes, rodents, covering themselves with peat, moss and wet leaves. It happens that they sometimes wake up for a whole week. Bog turtles spend the winter burrowing into the silt of ponds. Snakes don't like the cold. Even in summer, if you put a snake in the refrigerator for several hours, you can treat it like a piece of string. Therefore, snakes choose winter apartments carefully and choose for a long time. Usually these are underground caves and voids formed around large old stumps with rotten roots, or cracks in the rocks. in such shelters a large number of snakes gather even various kinds, forming huge balls. they sometimes have from several tens to hundreds of snakes, which has led to the erroneous opinion that snakes gather in balls to keep warm. Meanwhile, the temperature of the snakes during hibernation is almost the same as the ambient temperature, and they gather together simply from the lack of suitable shelters - some "dormitories" have been used for decades.
Many insects undergo periods of decreased metabolic activity called diapause. Diapause, which can occur at any stage of the life cycle—egg, nymph, larva, pupa, or adult, is usually characterized by cessation of growth in immature stages and cessation of sexual activity in adults. In some insects, this is a reaction to adverse environmental conditions; in others, such as certain moths and butterflies, diapause is a necessary stage in the life cycle. The 17-year larval and pupal periods of the cicada are examples of diapause.
How do animals manage to stay alive frozen? Just as when cold weather sets in, antifreeze is added to the radiator of cars, which freezes at minus 37 ° C, antifreeze proteins are formed in the body fluids of some cold-blooded animals in winter, which, when ice crystals appear in the body, bind to them and block further crystallization of water. in many fish, terrestrial arthropods, including spiders and mites, the effectiveness of antifreeze proteins is so great that it prevents the formation of ice even at minus 15 ° C. In addition to special proteins in the body of some cold-blooded creatures, antifreeze carbohydrates are also produced, which further reduce the point of maximum hypothermia. For example, in the tissues of many insects, the carbohydrate-antifreeze glycerol accumulates in winter, which successfully prevents freezing. in the caterpillars of the gall-forming butterfly, by the middle of winter, glycerol makes up 19% of the whole body, allowing them to supercool to minus 30 °C. And the hairy caterpillars of the arctic butterfly in the frozen state spend up to 10 months a year at minus 50 ° C and more! Originally adapted to low water temperatures, some fish living in the northern part of the Atlantic Ocean and in the Arctic waters - they change the composition of the blood. with a decrease in water temperature in autumn, salts accumulate in their blood in such a concentration that is characteristic of sea water, which enhances the cryoprotective effect, making it difficult for the blood to freeze. Relatively recently, special antifreeze proteins were found in the blood of these fish, lowering the freezing point of the solution to an even greater extent than salts.
This form of dormancy is especially common among insects living in arid desert regions, where during the dry and hot summers, insects usually hide in the soil at a suitable depth or under any available protective objects. Insects may be eggs, larvae, nymphs, pupae, or adults; because they can withstand very low temperatures, some of these forms will die if winter temperatures are within their normal range. Even rather fragile forms such as mosquitoes and butterflies survive in sheltered, relatively dry outdoor areas.
If a very severe wintering is ahead, then in the fall, cold-blooded animals (especially insects) accumulate cryogenic protectors protecting against ice, which increase the strength of cell membranes and prevent the so-called osmotic stress, when water from the cells tends to flow out into the extracellular environment with ice , reducing the volume of the cells and making them vulnerable to ice crystals piercing the shriveled cell walls. Cryoprotectors also serve as metabolic inhibitors. in a frog, for example, as soon as ice begins to form on the surface of the skin, the cryoprotectant glucose is rapidly synthesized from animal liver starch. as a result, after eight hours, all organs are saturated with it, metabolism slows down to a minimum, and energy consumption is limited. The record for this kind of use of cryoprotectants belongs to turtles - their metabolism drops to a level that ensures survival without oxygen consumption (!) throughout the winter. Moreover, at high concentrations of glucose in the body, there are no phenomena inherent in a person with a high content of glucose in the blood - diabetes mellitus and aging. The frost resistance of cold-blooded animals has always aroused the keen interest of scientists.
The annual life cycle of reptiles
Some butterflies even survive the winter in low scrub where they can be completely covered in snow and ice for three or four months. Other insects prepare for winter by building nests or cocoons; others seek suitable hiding places. Among some insect species, diapause lasts only until favorable environmental conditions appear, after which the insect resumes its normal activities. In other species, favorable environmental conditions do not disrupt diapause; some other stimulus is needed, such as cold or food.
Some species of higher plants also fall into an anabiotic state. The record in this regard belongs to the armored plant found in the prairies of the American continent. Placed in a herbarium, this plant withstood as much as 11 years in a dried state without losing its viability. The question inevitably arises: what helps plants to endure severe dehydration and fall into a state of suspended animation, in which the metabolism is so slow that it is practically almost zero? According to scientists, during dehydration in plants capable of falling into an anabiotic state, the respiration process is not disturbed, which retains its so-called energy usefulness. When dehydrated, plants continue to produce energy-rich compounds such as ATP (adenosine triphosphate). The energy generated in the process of respiration until these plants are almost completely dry is transferred to almost all cellular structures and all cellular contents, which, when dehydrated, passes into a jelly-like state, and the cells can remain viable for years.
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