Distinctive features of marsupials. What animals are representatives of marsupial mammals

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"Marsupials" report

Marsupials belong to the subclass of mammals. Among them are herbivores and predators, omnivores and insectivorous animals, scavengers. Some live on the ground, others in trees, underground or near water. About 280 species of marsupials are known on the planet - the most famous of them are predatory marsupials, kangaroos, American opossums, bandicoots and possums. They are not related to placental mammals.

Where do marsupials live?

The distribution of marsupials is rather peculiar. Most of them live in Australia, Tasmania, New Zealand and New Guinea. In America, marsupial opossums are found.

Brief description of marsupials

There are many primitive features in their structure. The body of animals is covered with thick hair, and the subcutaneous glands produce dyes and substances. Body temperature depends on temperature environment. The teeth of marsupials immediately grow permanent. For marsupials, the presence of various adaptations to a particular habitat is characteristic - powerful claws for digging, strong paws for holding on trees, tenacious tail for climbing, strong hind legs for jumping. Their cubs are born underdeveloped, after which they actively develop in the mother's pouch on her belly. Brood bag is a special skin fold on the abdomen. At certain types she is absent. All representatives of marsupials have bones that support the stomach. They are located in the pelvic girdle. This distinguishes marsupials from other mammals. Also their distinguishing feature in that females have a double vagina and double uterus, and most males have a dilobed penis.

Reproduction of marsupials

Pregnancy is quite long short period, after which underdeveloped cubs up to 3 cm long are born. They are covered with pinkish transparent skin, the front legs are already formed with claws and a developed tail. It is born from a hole near the base of the tail and, wriggling like a lizard, with the help of strong muscles, moves into the mother's pouch. If the baby could not resist and fell - he dies. The cub, once in the bag, clings to the nipple, which clogs the mouth of the newborn and the milk goes directly into his mouth. The kids seem to hang on them. In the bag, it grows and develops. Rarely leaves her. When the animal can already get its own food, it leaves the female.

In animals without a pouch, babies grow on their mother's back. They are protected by her dense, warm fur. These include marsupial anteater and rat-like opossums.

Nutrition of marsupials

Marsupials feed on grasses, leaves and young shoots of trees, algae, and bark. Other species prefer various insects. Others are predators and scavengers: they eat invertebrates, birds, eggs, small mammals, animal carcasses. It all depends on the species.

• The largest marsupial is the red kangaroo. His height is higher than the height of a person, and his weight reaches 90 kg.
• The smallest marsupial is the wallaby, a small kangaroo.
• Kangaroos can live for several months without water.
• Some representatives have toxic substances in their saliva.
• Young marsupials are born no larger than a peanut. After they develop and grow in the mother's pouch.
• Kangaroo big ears. When they hear danger, they beat their paws on the ground to warn their relatives.
• Kangaroos know how to fight and can kill a person with their blow.

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Marsupials ( Marsupialia) are a group (infraclass) of mammals. Like most other mammalian species, they give birth to live young, but only on early stage development. In some species, such as bandicoots ( Peramelemorphia), the gestation period is as short as 12 days. Newborn baby marsupials crawl over the mother's body into a bag located on her stomach. Once inside the pouch, the baby attaches itself to the mother's nipple and feeds on milk until it is large enough to live in the outside world.

While large marsupials tend to give birth to a single young, smaller species are more likely to produce large litters.

Marsupials were common in many areas during and outnumbered placental mammals. Today, the only living marsupial in North America is the opossum.

Marsupials first appear in the record from during the Late Paleocene. They later appear in the fossil record from during the Oligocene, where they diversified during the early Miocene. The first large marsupials appeared during the Pliocene.

Distribution map modern marsupials/Wikipedia

Today, marsupials remain one of the dominant mammal groups in South America and Australia. In Australia, the lack of competition has led marsupials to be able to diversify and specialize. Today the continent is inhabited by insectivorous marsupials, carnivorous marsupials, and herbivorous marsupials. Most South American marsupial species are small and arboreal.

The reproductive tract of female marsupials differs from placental mammals. They have two vaginas and two uteri, while placental mammals have one uterus and one vagina. Distinctive features Male marsupials also have genital organs - they have a bifurcated penis. The brain of marsupials is also unique, it is smaller than that of placental mammals, there is no corpus callosum and nerve pathways that connect the two hemispheres of the brain.

Marsupials are very diverse in appearance. Many species have long hind legs and elongated snouts. Most small view marsupials is the northern marsupial and the largest is the red kangaroo. To date, there are about 334 species of marsupial mammals, of which 70% of the species are found on the Australian continent (including Tasmania, New Guinea and nearby islands). The remaining 100 species are found in the Americas - mostly in South America, thirteen in Central America and one in North America, north of Mexico.

Classification

Marsupials are classified in the following taxonomic hierarchy:

⇒ ⇒ ⇒ ⇒ ⇒ ⇒ Marsupials

Marsupials are divided into two modern superorders and seven orders:

• Superorder American marsupials ( Ameridelphia) - there are about 100 species of marsupials living today. American marsupials are the older of the two contemporary bands, which means that the members of this group migrated to Australia and diversified. Superorder Ameridelphia subdivided into the following two divisions:
  • Possum Squad ( Didelphimorphia);
  • Caenoleste detachment ( Paucituberculata).

• Superorder Australian marsupials ( Australidelphia) - there are more than 200 species of Australian marsupials living today. Members of this group include Tasmanian devils, marsupial anteaters, bandicoots, wombats, marsupial moles, pygmy opossums, koalas, kangaroos, wallabies, and many other species. Australian marsupials are divided into five orders:
  • Detachment Microbiota ( Microbiotheria), found in South America;
  • Squad Marsupial moles ( Notoryctemorphia);
  • Order Predatory marsupials ( Dasyuromorphia);
  • Bandicoot Squad ( Peramelemorphia);
  • Detachment Dicissus marsupials ( Diprotodontia), includes most modern species marsupials.

Marsupials, with the exception of American possums, are common on the Australian mainland, New Guinea and nearby islands. About 200 species from 9 families belong to this order. Among the marsupials there are insectivorous, predatory and herbivorous forms. They also differ greatly in size. The length of their body, including the length of the tail, can range from 10 cm (Kimberley marsupial mouse) to 3 m (large gray kangaroo).

Marsupials are more complexly organized animals than monotremes. Their body temperature is higher (on average + 36 °). All marsupials give birth to live young and feed them with milk. However, compared with the higher mammals, they have many ancient, primitive structural features that sharply distinguish them from other animals.

First feature marsupials- the presence of the so-called marsupial bones (special bones of the pelvis, which are developed in both females and males). Most marsupials have a pouch for carrying young, but not all have it to the same degree; there are species in which the bag is missing. Most primitive insectivorous marsupials do not have a “finished” bag - a pocket, but only a small fold that limits the milky field. This is the case, for example, with numerous marsupial mice, or mouse species. The yellow-footed marsupial mouse - one of the most archaic marsupials - has only a slight uplift of the skin, like a border around the milky field; the fat-tailed marsupial mouse close to it has two lateral folds of skin, which grow somewhat after the birth of cubs; finally, the baby mouse has something that looks like a bag that opens back towards the tail. In kangaroos, the bag of which is more perfect, it opens forward, towards the head, like an apron pocket.

Second salient feature marsupials- this is a special structure of the lower jaw, the lower (posterior) ends of which are bent inward. The coracoid bone in marsupials is fused with the scapula, as in higher mammals - this distinguishes them from monotremes.

The structure of the dental system is an important classification feature of the order of marsupials. On this basis, the entire detachment is divided into 2 suborders: multi-incisor and two-incisor. The number of incisors is especially large in primitive insectivorous and predatory forms, which have 5 incisors in each half of the jaw at the top and 4 incisors at the bottom. Herbivorous forms, in contrast, have no more than one incisor on each side of the lower jaw; their fangs are absent or underdeveloped, and their molars have blunt tubercles.

The structure of the mammary glands of marsupials is characteristic; they have nipples to which newly born cubs are attached. The mammary ducts open at the edge of the nipples, as in monkeys and humans, and not into an internal reservoir, as in most mammals.

However, the main difference between marsupials and all other mammals is the features of their reproduction. The process of reproduction of marsupials, the observation of which is very difficult, has only recently been fully elucidated.

The cubs in the mother's pouch are at first so small and underdeveloped that the first observers had a question: would they not be born directly in the pouch? F. Pelsart, a Dutch navigator, in 1629 first described a marsupial. He, like many later naturalists, thought that the young of marsupials are born right in the bag, "from the nipples"; according to these ideas, the cub grows on the nipple, like an apple on a tree branch. It seemed incredible that a half-formed embryo, hanging inertly on the nipple, could climb into the pouch on its own if it was born outside of it. However, already in 1806, the zoologist Barton, who studied the North American opossum, found that the newborn can move around the mother's body, get into the bag and attach to the nipple. For Australian animals this was confirmed in 1830 by the surgeon Colley. Despite these observations, the famous English anatomist R. Owen in 1833 returned to the already expressed idea that the mother carries the newborn into the bag. According to Owen, she takes the cub with her lips and, holding the opening of the bag with her paws, puts it inside. The authority of Owen for more than half a century fixed this incorrect point of view in science.

The embryo in marsupials begins to develop in the uterus. However, it is almost not connected with the walls of the uterus and to a large extent is only a “yolk sac”, the contents of which are quickly depleted. Long before the embryo is fully formed, it has nothing to eat, and its "premature" birth becomes a necessity. The duration of pregnancy is very short, especially in primitive forms (for example, in an opossum or in marsupial cats from 8 to 14 days, in a koala it reaches 35, and in a kangaroo - 38-40 days).

The newborn is very small. Its dimensions do not exceed 25 mm in a large gray kangaroo - the largest representative of the detachment; in primitive insectivores and predators, it is even smaller - about 7 mm. The weight of the newborn is from 0.6 to 5.5 g.

The degree of development of the embryo at the time of birth is somewhat different, but usually the cub is almost devoid of hair. The hind limbs are poorly developed, bent and closed by the tail. On the contrary, the mouth is wide open, and the front legs are well developed, claws are clearly visible on them. The forelimbs and mouth are the organs that a newborn marsupial will need first.

No matter how underdeveloped the marsupial cub may be, it cannot be said that it is weak and lacks energy. If you separate him from his mother, he can live for about two days.

Kangaroo rats and some possums have only one baby; koalas and bandicoots sometimes have twins. Most insectivorous and predatory marsupials have much more babies: 6-8 and even up to 24. Usually the number of babies corresponds to the number of mother's nipples to which they must attach. But often there are more cubs, for example, in marsupial cats, in which there are only three pairs of nipples for 24 cubs. In this case, only the first 6 cubs attached can survive. There are also opposite cases: in some bandicoots, which have 4 pairs of nipples, the number of cubs does not exceed one or two.

To attach to the nipple, the newborn must enter the mother's pouch, where protection, warmth, and food await. How does this movement take place? Let's trace it on the example of a kangaroo.

A newborn kangaroo, blind and underdeveloped, very soon chooses the right direction and begins to crawl straight to the bag. It moves with the help of front paws with claws, wriggling like a worm, and turning its head around. The space in which he crawls is covered with wool; this, on the one hand, hinders him, but, on the other hand, helps: he clings tightly to the wool, and it is very difficult to shake him off. Sometimes the calf makes a mistake in direction: it crawls to the mother's thigh or chest and turns back, searching until it finds a bag, searching continuously and tirelessly. Finding the bag, he immediately climbs inside, finds the nipple and attaches to it. Between the moment of birth and the time when the cub is attached to the nipple, in large kangaroos, it usually takes from 5 to 30 minutes. Attached to the nipple, the cub loses all its energy; he again for a long time becomes an inert, helpless embryo.

What does the mother do while her cub is looking for a bag? Does she help him in this difficult moment? Observations on this are still incomplete, and opinions are rather contradictory. During the time it takes for the newborn to reach the pouch, the mother takes a position and does not move. Kangaroos usually sit on the tail passing between the hind legs and pointing forward, or lying on their side. The mother holds her head as if she is watching the cub all the time. Often she licks it - immediately after birth or during the movement to the bag. Sometimes she licks her hair towards the bag, as if helping the cub to move in the right direction.

If the cub gets lost and cannot find the bag for a long time, the mother begins to worry, scratch and fidget, while she can injure and even kill the cub. In general, the mother is more of a witness to the energetic activity of the newborn than his assistant.

Initially, the nipple has an elongated shape. When a cub is attached to it, a thickening develops at its end, apparently associated with the release of milk; this helps the baby stay on the nipple, which he squeezes with his mouth all the time. It is very difficult to separate it from the nipple without tearing its mouth or damaging the glands.

The baby passively receives milk, the amount of which is regulated by the mother with the help of contractions of the muscles of the milky field. For example, in a koala, the mother supplies the cub with milk for 5 minutes every 2 hours. So that he does not choke on this stream of milk, there is a special device respiratory tract: air passes directly from the nostrils into the lungs, since the palatine bones at this time are not yet fully formed, and the epiglottic cartilage continues forward to the nasal cavity.

Protected and supplied with food, the cub grows rapidly. The hind legs develop, usually becoming longer than the front ones; the eyes open, and after a few weeks the immobility is replaced by conscious activity. The baby begins to break away from the nipple and stick its head out of the bag. The first time he wants to get out, he is not allowed to go by his mother, who can control the size of the outlet of the bag. Different types marsupials spend a different period in the bag - from several weeks to several months. The stay of the cub in the bag ends as soon as it becomes able to feed not on milk, but on other food.

The mother usually looks for a nest or a lair in advance, where the children live under her supervision for the first time.

The order of marsupials (Marsupialia) is divided into 2 suborders: multi-cutting(Polyprotodontia) and two-blade(Diprotodontia). The former include more primitive insectivorous and predatory individuals, the latter - herbivorous marsupials. An intermediate position between the multi-incisors and the two-incisors is occupied by a little-studied group of coenolests, which some zoologists consider to be a separate suborder. The coenolest group includes one family and three genera. These are small animals that resemble American opossums and are found in South America.

Animal life: in 6 volumes. - M.: Enlightenment. Edited by professors N.A. Gladkov, A.V. Mikheev. 1970 .

Order marsupials

In the class of mammals, the order of marsupials, more than others, can attract our attention. Under the name of marsupials, we unite a significant number of diverse families of mammals, which, with the exception of the bag, the method of reproduction and the genital organs, have very little in common with each other. They could rather be considered as detachments of a special subclass of mammals*.

* Within the class of mammals, marsupials and placentals constitute a subclass of animals (Theria), opposed to a subclass of first animals (Prototheria).

When studying the animals belonging to this region, the thought arises that we are dealing with a group that flourished especially at a time when huge clumsy amphibians, flying lizards and sea ​​monsters like an ichthyosaur. Very strong arguments suggest that marsupials are only slightly modified descendants of past mammals. geological periods. A more detailed study of marsupials and their comparison with other mammals reveal that their appearance is very diverse and they often resemble representatives of other orders; but it is no less striking that their organization is more imperfect than those animals to which they resemble. If you do not pay attention to the bag, then the marsupial wolf in appearance undoubtedly resembles a dog, marsupial marten - with a civet, marsupial mouse - with a shrew, a wombat - with a rodent, just like a marsupial squirrel resembles a flying squirrel, and the kangaroo appears to have the head of a ruminant. However, the dental system internal structure these marsupials show fundamental differences from the representatives of higher orders compared with them, and this does not allow them to be connected.
If we compare a marsupial with a predator or rodent, it becomes clear even to the most impenetrable eye that it is in every respect less developed and less perfect than a similar predator or rodent. This backwardness of the marsupial is manifested either in the form of the whole body, or in the structure of individual organs, or in the dental system. Our eye, accustomed to other forms of animals, always lacks something when looking at a marsupial. Their dental system, in comparison with the dental systems of the corresponding predators and rodents, turns out to be more imperfect and meager. The jaws of a predatory marsupial are equipped with a sufficient number of teeth, and their order is the same as that of predators. But they are less developed, or misplaced, or much duller, sometimes worse in color, less white and clean than the teeth of a real predator of later times. Thus, we can quite reasonably accept that we are dealing with imperfect, still insufficiently developed beings*.

* Marsupials evolved in a relatively limited space of three southern continents. In "greenhouse" conditions, marsupials did not need to constantly complicate their behavioral reactions and skills. The brain of marsupials practically did not change, remained small and simply arranged. This is the reason for the "primitiveness" and "stupidity" of modern marsupials emphasized by Brehm. When the "real beasts" invaded southern continents during the late Caenozoic faunal exchange. the marsupials did not hold their positions and now exist as relics only where the placentals occupying the corresponding niche have not penetrated.

In general, very little can be said about the body structure of marsupials in general. The various members of this order are more distinct from each other than the members of any other order. You can specify some general features of the skeleton. The skull is for the most part conically elongated; the braincase, compared with the facial part and with the nasal cavity, is smaller than in the animals we have already spoken about; individual bones do not fuse as early and closely as those of those. The vertebral column usually consists of 7 cervical vertebrae, 12-15 rib-bearing vertebrae, 4-6 lumbar, 2-7 sacral and various numbers of caudal, since the tail is either completely invisible from the outside or underdeveloped, it reaches extremely large sizes. The clavicle, with the exception of a few species, always exists; the structure of the fore and hind limbs, on the contrary, is very diverse. The brain is characterized by insignificant development: the cerebral hemispheres are almost completely flat, which does not speak in favor of marsupials and explains their rather insignificant degree of development. mental capacity. The stomach in species that feed on meat, insects and fruits is simple and rounded, in others it is markedly elongated; the intestine can also represent a very diverse structure. The teeth of marsupials are similar in only one respect to the teeth of more developed mammals: they are partly replaceable. In all other respects, they differ very significantly. Most marsupials are especially distinguished by a significant number of teeth. The fangs, which are very large in meat-eating animals, are poorly developed in plant-eating animals, and in many they are completely absent. The number of incisors is usually not the same in both jaws; false-rooted with two roots; true molars are sharp-tuberous or equipped with folds of enamel various shapes. All representatives of the order have the same structure of the genital organs and the presence of the bones of the bags. In the female, they strengthen the abdominal wall and protect the young in the pouch from the pressure of the mother's abdominal viscera. The pouch contains the mammary glands, to which babies born prematurely are sucked. The pouch may represent a real pocket, or be underdeveloped, forming two leathery folds, or even be in its infancy. Cubs are born in such a state as none of the higher mammals. They are small, naked, blind and have only rudimentary limbs. After birth, they stick to one of the nipples, which usually look like a long conical wart and soon grow noticeably. Then they develop rapidly, leave the nipple at times and crawl out of the bag.
From the day of conception until the cub can stick its head out of the bag, it takes about 7 months for a gigantic kangaroo; from this time until he leaves the bag for the first time, about 9 weeks more, and for the same time the young kangaroo then lives partly in the bag, partly outside. The number of cubs can be very significant*.

* The size of the cubs at birth does not exceed 0.5-3 cm. In one litter there can be from one to 25 (a record among mammals!) newborns.

As already noted, marsupials currently inhabit Australia and some of the adjacent islands, as well as South and North America. In America, there are only representatives of one family, mainly in its southern part **.

* * The variety of life forms of marsupials in South America during most of the Cenozoic was almost as good as that in Australia. In addition to the possums and coenolests that have survived to this day, there lived large predators and small herbivorous analogues of rodents. Most of the marsupials of the continent did not survive the placental invasion; but when the land connection between the North and South America, then some opossums re-colonized North and Central America.

Various types of marsupials also have little in common in their way of life: some of them are predators, others feed on plants; many live on the ground, others in the trees, some at times even in the water; most are nocturnal animals, some, however, are active during the day. Of the carnivores, many dexterously run and climb; of those that feed on plants, some are fast and hardy in running. However, it is impossible not to notice that even the most perfect marsupials are far from achieving the mobility of more developed mammals. The kangaroo is inferior to the deer or antelope, and the wombat to even the most clumsy rodent. The same applies to the mental abilities of marsupials; and in this respect they cannot be compared with other beasts. They have only external senses, perhaps at the same level as other mammals; their comprehension, on the contrary, is always negligible. Each marsupial, in comparison with the approximately corresponding higher mammal, is a stupid creature, not amenable to either training or education. It is impossible to raise a dog from a marsupial wolf, which has almost a human mind. The imperfection, rudeness and clumsiness of marsupials is especially clearly revealed in their manners and habits.
The food of the marsupials the highest degree varied. All species that correspond to predators chase other animals, eat shellfish, fish and other prey thrown up by the sea, or carrion of land animals; smaller species prey on birds, insects, and worms. Herbivores feed on fruits, leaves, herbs, and roots, which they pluck or pluck. Predatory marsupials sometimes cause harm and annoyance, chasing herds, climbing into chicken coops at night and causing other troubles. Europeans exterminate marsupials as quickly as possible, without any specific purpose, but only to satisfy an unbridled passion for hunting. At the same time, the meat and skin of only a few species are used, and the rest are not needed for anything.

Life of animals. - M.: State publishing house of geographical literature. A. Brem. 1958

See what the "Marsupial Squad" is in other dictionaries:

Marsupials, with the exception of American possums, are common on the Australian mainland, New Guinea and nearby islands. About 200 species from 9 families belong to this order. Among the marsupials there are insectivores, ... ... Biological Encyclopedia

Systematicbelonging

Kingdom: Animals
Type of: chordates
Subtype: Vertebrates
Class: mammals
Infraclass: marsupials

Features of the external structure

With the exception of American opossums and coenolests, common, on the Australian mainland, New Guinea and nearby islands.
About 250 species belong to this order.. Among the marsupials there are insectivorous, carnivorous and herbivorous forms.. Very differentthey are in size.
The length of their body, including the length of the tail, can range from 10 cm(marsupialmouse Kimberly) up to 3 m (large gray kangaroo).Marsupials are more difficult
organized animals than monotremes. Their body temperature is higher (on average - 36 °).

The tail of most marsupials is well developed, in climbing forms (some opossums and possums) it can be prehensile.
The limbs are usually five-fingered. Most often, the 1st and 5th fingers are reduced. In a number of forms (kangaroo, etc.), the 2nd and 3rd fingers grow together along the entire length. In many climbing forms (koala, couscous, etc.), the first one or two fingers are opposed to the rest. In burrowing forms (badgers, moles), the claws on the forelimbs are greatly enlarged. In jumping forms (jerboa, kangaroo), the hind limbs are elongated, the forelimbs are shortened, and the tail is long. The hairline is dense, often soft, sometimes bristly. Vibrissae are well developed on the muzzle and limbs. In a number of tree forms, the prehensile tail is completely or only at the end devoid of hair. The coloration is usually monophonic, patronizing, less often spotted (martens) or striped (marsupial wolf).
A characteristic feature of marsupials is the presence of so-called marsupial bones (special bones of the pelvis, which are developed in both females and males). Most marsupials have a pouch for carrying young, but not all have it to the same degree; there are species in which the bag is missing. Most primitive insectivorous marsupials do not have a “finished” bag - a pocket, but only a small fold that limits the milky field.

Features of the internal structure

The second characteristic feature of marsupials is the special structure of the lower jaw, the lower (posterior) ends of which are bent inward. The coracoid bone in marsupials is fused with the scapula, as in higher mammals - this distinguishes them from monotremes. The structure of the dental system is an important classification feature of the order of marsupials. On this basis, the entire detachment is divided into 2 suborders: multi-incisor and two-incisor. The number of incisors is especially large in primitive insectivorous and predatory forms, which have 5 incisors in each half of the jaw at the top and 4 incisors at the bottom. Herbivorous forms, in contrast, have no more than one incisor on each side of the lower jaw; their fangs are absent or underdeveloped, and their molars have blunt tubercles. The structure of the mammary glands of marsupials is characteristic; they have nipples to which newly born cubs are attached.

The ducts of the mammary glands open at the edge of the nipples, as in monkeys and humans, and not into the internal reservoir, as in most mammals.

AT circulatory system Cuvier ducts are present. The vagina and uterus are double. The typical placenta (with the exception of badgers) does not develop.

All parts of the spine are developed normally. Everyone has a clavicle (except S. badgers).

reproduction feature. Exceptional Feature

However, the main difference between marsupials and all other mammals is the features of their reproduction. The process of reproduction of marsupials, the observation of which is very difficult, has only recently been fully elucidated.

AT In 1806, the zoologist Barton, who studied the North American opossum, found that the newborn can move around the mother's body, climb into the bag and attach to the nipple. The authority of the zoologist for more than half a century has fixed this incorrect point of view in science.

The embryo in marsupials begins to develop in the uterus. However, it is almost not connected with the walls of the uterus and to a large extent is only a “yolk sac”, the contents of which are quickly depleted. Long before the embryo is fully formed, it has nothing to eat, and its "premature" birthbecomes a necessity.

The duration of pregnancy in marsupials is very short, especially in primitive forms. The newborn is very small. The weight of the newborn is from 0.6 to 5.5 g. The degree of development of the embryo at the time of birth is somewhat different, but usually the cub is almost devoid of hair. The hind limbs are poorly developed, bent and closed by the tail. On the contrary, the mouth is wide open, and the front legs are well developed, claws are clearly visible on them. The forelimbs and mouth are the organs that a newborn marsupial will need first.

No matter how underdeveloped the marsupial cub may be, it cannot be said that it is weak and lacks energy. If you separate him from his mother, he can live for about two days. Kangaroo rats and some possums have only one baby; koalas and bandicoots sometimes have twins. Most insectivorous and predatory marsupials have much more babies: 6-8 and even up to 24. Usually the number of babies corresponds to the number of mother's nipples to which they must attach. But often there are more cubs, for example, in marsupial cats, in which there are only three pairs of nipples for 24 cubs. In this case, only the first 6 cubs attached can survive. There are also opposite cases: in some bandicoots, which have 4 pairs of nipples, the number of cubs does not exceed one or two. To attach to the nipple, the newborn marsupial must get into the mother's pouch, where protection, warmth and food await it.

Let's trace the movement on the example of a kangaroo. A newborn kangaroo is underdeveloped, very soon chooses the right direction and begins to crawl straight to the bag. It moves with the help of front paws with claws, wriggling like a worm, and turning its head around. The space in which he crawls is covered with wool; this, on the one hand, hinders him, but, on the other hand, helps: he clings tightly to the wool, and it is very difficult to shake him off. Finding the bag, he immediately climbs inside, finds the nipple and attaches to it. Between the moment of birth and the time when the cub is attached to the nipple, marsupials usually have 5 to 30 minutes. Attached to the nipple, the cub loses all its energy; he again for a long time becomes an inert, helpless embryo. During the time it takes for the newborn to reach the pouch, the mother takes a position and does not move. Kangaroos usually sit on the tail passing between the hind legs and pointing forward, or lying on their side. The mother holds her head as if she is watching the cub all the time. Often she licks it - immediately after birth or during the movement to the bag. Sometimes she licks her hair towards the bag, as if helping the cub to move in the right direction. If the cub gets lost and cannot findWith umku, the mother begins to worry, itch and spin, while she can injure and even kill the cub.

Initially, the nipple of marsupials has an elongated shape. When a cub is attached to it, a thickening develops at its end, apparently associated with the release of milk; this helps the baby stay on the nipple, which he squeezes with his mouth all the time. It is very difficult to separate it from the nipple without tearing its mouth or damaging the glands. The baby of marsupials passively receives milk, the amount of which is regulated by the mother with the help of muscle contractions of the milky field. For example, in a koala, the mother supplies the cub with milk for 5 minutes every 2 hours. So that he does not choke on this stream of milk, there is a special arrangement of the respiratory tract: air passes directly from the nostrils to the lungs, since the palatine bones at this time have not yet been fully formed, and the epiglottic cartilage continues forward to the nasal cavity.