Characteristic features of monotremes. Oviparous mammal: description, features, reproduction and types
Following the discovery of the platypus came news of another creature with a beak, only now it is covered in spines. This is an echidna. For a long time, scientists argued about which class to classify these two creatures into. And they came to the conclusion that the platypus and echidna, egg-laying mammals, should be placed in a separate order. This is how the order Monotremes, or Cloacae, appeared.
The Amazing Platypus
A unique creature of its kind, leading night look life. The platypus is widespread only in Australia and Tasmania. The animal lives half in water, that is, it builds holes with access to water and land, and also feeds in water. The creature is small in size - up to 40 centimeters. It has, as already mentioned, a duck's nose, but at the same time it is soft and covered with skin. It just looks very similar to a duck. It also has a 15 cm tail, similar to that of a beaver. The paws are webbed, but they do not prevent the platypus from walking on the ground and digging holes well.
Since the animal’s genitourinary system and intestines exit into one opening, or cloaca, it was classified as separate species- Cloacal. It is interesting that the platypus, unlike ordinary mammals, swims with the help of its front legs, and the hind legs serve as a rudder. Among other things, let's pay attention to how it reproduces.
Platypus breeding
Interesting fact: before breeding, animals hibernate for 10 days, and only after that the mating season begins. It lasts almost all autumn, from August to November. Platypuses mate in water, and after a period of two weeks, the female lays an average of 2 eggs. Males do not participate in the future life of the offspring.
The female builds a special burrow (up to 15 meters long) with a nest at the end of the tunnel. Lines it with damp leaves and stems to maintain a certain humidity so that the eggs do not dry out. Interestingly, for protection she also builds a barrier wall 15 centimeters thick.
Only after preparatory work does she lay eggs in the nest. The platypus incubates eggs by curling up around them. After 10 days, babies are born, naked and blind, like all mammals. The female feeds the babies with milk, which flows from the pores directly along the fur into the grooves and accumulates in them. Babies lick the milk and feed in this way. Feeding lasts about 4 months, and then the babies learn to get food on their own. It is the method of reproduction that gives this species the name “oviparous mammal.”
Extraordinary echidna
The echidna is also an oviparous mammal. This is a land creature small sizes, reaching up to 40 centimeters. It also lives in Australia, Tasmania and the islands of New Guinea. In appearance, this animal is similar to a hedgehog, but with a long narrow beak not exceeding 7.5 centimeters. Interestingly, the echidna has no teeth, and it catches prey with the help of a long sticky tongue.
The echidna's body is covered on the back and sides with spines, which are formed from coarse wool. Wool covers the belly, head and paws of the animal. The echidna is fully adapted for a specific type of food. She feasts on termites, ants and small insects. She leads daytime look life, although it is not easy to detect. The fact is that she has a low body temperature, up to 32 degrees, and this does not allow her to tolerate a decrease or increase in temperature environment. In this case, the echidna becomes lethargic and rests under the trees or hibernates.
Echidna breeding method
The echidna is an oviparous mammal, but this was only proven in beginning of XXI century. Interesting mating games echidna There are up to 10 males per female. When she decides she is ready to mate, she lies down on her back. At the same time, the males dig a trench around her and begin to fight for primacy. The one who is stronger copulates with the female.
Pregnancy lasts up to 28 days and ends with the appearance of one egg, which the female moves into the brood fold. It is still not clear how the female moves the egg into the pouch, but after 10 days the baby appears. The cub comes into the world not fully formed.
Young
The birth of such a baby is very similar to the birth of marsupial cubs. They also undergo final development in their mother’s pouch and leave her as adults, ready for independent life. Interesting fact: marsupial mammals also common only in Australia.
How does a baby echidna appear? He is blind and naked, his hind limbs are not developed, his eyes are covered with a leathery film, and only his front paws have digits. It takes a baby 4 hours to get to milk. Interestingly, the mother has 100-150 pores in her pouch, which secrete milk through special hairs. The baby just needs to get to them.
The baby stays in the mother's pouch for about 2 months. He gains weight very quickly thanks to nutritious milk. Echidna milk is the only one that has a pink color due to large quantity it contains iron. Breastfeeding continues up to 6.5 months. Afterwards, the young animals learn to get food on their own.
Prochidna
The echidna is another oviparous mammal. This creature is much larger than its fellows. Habitat is the north of New Guinea and the islands of Indonesia. The size of the echidna is impressive, up to 80 centimeters, and its weight is up to 10 kilograms. It looks like an echidna, but the beak is much longer and the needles are much shorter. It lives in mountainous areas and feeds mostly on worms. The structure of the echidna’s oral cavity is interesting: its tongue has teeth, and with the help of it it is capable of not only chewing food, but, as has been noted, even turning over stones.
This species is the least studied, as it lives in the mountains. But at the same time, it was noticed that the animal does not lose mobility in any weather, does not hibernate, and is able to regulate its own body temperature. Reproduction of oviparous mammals, which includes the echidna, occurs in the same way as in the other two species. She hatches only one egg, which is placed in a pouch on her stomach, and feeds the baby with milk.
Comparative characteristics
Now let's look at the species of mammals that live on the Australian continent. So, what is the difference between oviparous, marsupial and placental mammals? To begin with, it must be said that all mammals feed their offspring with milk. But the birth of babies has huge differences.
Oviparous animals have one common feature. They lay eggs like birds and hatch them for a certain period of time. After the birth of the offspring, the mother’s body produces milk, which the babies feed on. It should be noted that the cubs do not suck milk, but lick it from the grooves on the female’s abdomen. The absence of nipples distinguishes oviparous mammals from other mammals.
Marsupial mammals have a brood pouch, hence their name. The pouch is located on the abdomen of females. The newborn baby, having reached it, finds the nipple and seems to hang on it. The fact is that babies are born unformed and spend several more months in their mother’s pouch until they are fully developed. It must be said that oviparous and marsupial mammals have similarities in this regard. Baby echidnas and proechidnas are also born underdeveloped and are placed in a kind of brood fold.
What about placental mammals? Their babies are born fully formed due to the presence of the placenta in the uterus. Due to it, the process of nutrition and development of the baby occurs. The bulk of animals are placental.
This is the diversity of species that exists on one continent.
Order Monotremes
Monotremes are rightly considered representatives special squad and even a subclass of mammals*.
* A separate subclass of oviparous mammals, or proto-beasts (Prototheria), in the modern fauna is represented only by the order of monotremes, known since the Early Cretaceous. Monotremes live only in Australia and the surrounding islands.
That monotremes actually feed their young with milk has long been established beyond any doubt; but only Gegenbaur's precise researches introduced us to the true nature of their mammary glands. Previously, they were not noticed for a long time and therefore, already at the beginning of this century, they were confident in the correctness of the indication made by the researcher who first discovered the platypus, namely, that the platypus lays eggs; Later this indication was considered a fable. But on September 2, 1884, Haacke informed the Royal South Australian Society in Adelaide that a few weeks earlier he had found an egg in a large, hitherto unknown pouch of a living female echidna, which he showed at the meeting. On the same day, a telegram was read in Montreal informing the members of the British Association assembled there that another researcher working at that time in Australia, Caldwell, was convinced that monotremes lay eggs. Gegenbaur proved in 1886 that the glands that deliver food to the young monotremes emerging from the eggs do not correspond in structure to the sebaceous glands, as in other mammals, but are modified sweat glands. If we add to this that during a significant period of its life the platypus has, although real teeth, very different from the teeth of all other living mammals, as Thomas discovered only in 1888, and that, in contrast to all other warm-blooded animals, the temperature of the blood monotremes does not exceed 28 degrees Celsius**, it will not seem strange if we separate them as the second main division of the class of mammals from the first, to which we must classify them as true mammals, marsupials and higher mammals, vertebrates.
* * The body temperature of the platypus is on average 32.2 degrees Celsius, and that of the echidna is 31.1 degrees. Representatives of the order still have imperfect thermoregulation mechanisms, and the temperature can fluctuate between 25-36 degrees.
Monotremes are similar to other mammals primarily in their outer coverings: the platypus has fur, and the echidna has spines; in other respects, and in appearance, they differ significantly from other known forms of this class. A horny beak, reminiscent of the beak of swimming birds, replaces their muzzle; The excretory ducts of the intestines, urinary and genital organs open together into the so-called cloaca. We find this formation again in birds, which monotremes resemble, except for eggs with a large yolk, also in the presence of an arch formed from clavicles fused together, and in the fact that their right ovary is partly underdeveloped. If in this way one cannot help but notice their relationship with birds, as well as with reptiles and amphibians, then they are connected with marsupials by the presence of marsupial bones in the pelvis.
Monotremes are small mammals with a dense body, somewhat flattened from top to bottom, very short legs, beak-shaped jaws covered with dry skin, small eyes, a short tail, legs spread outward with large claws; the male has a hollow spur on the heel, which is connected to a special gland. There is no external auricle at all; the teeth, which exist only in the platypus, consist of flat saucer-shaped plates, equipped with tubercles or grooves at the edges, which are adjacent to the jaws. On the skull, many sutures fuse very early; The costal cartilages also completely ossify. Salivary glands are large, the stomach is simple, the cecum is very short. There is no real uterus, as the oviducts open into the cloaca*.
* The stomach of unitemporal animals is devoid of digestive glands and serves only for storing food, like the crop of birds. The structure of the limbs is very similar to that of a reptile; when walking, the legs are not under the body, like in other animals, but are widely spaced apart, like in crocodiles or lizards.
In addition to the bones of one extinct echidna, the teeth of fossil animals were found, which are similar to the teeth of the platypus; Currently, this peculiar order is limited to two families - echidnas and platypuses.
Life of animals. - M.: State Publishing House of Geographical Literature. A. Brem. 1958.
See what “Order Monotremes” is in other dictionaries:
Monotremes (or oviparous) are the most primitive among modern mammals, which have preserved a number of archaic structural features inherited from reptiles (egg laying, the presence of a well-developed coracoid bone not connected to ... Biological encyclopedia
One of the subclasses of mammals are oviparous animals. In this article we will talk in detail about the representatives of this group, outline their characteristics and habitat.
general characteristics
Monotreme mammals have several names, such as oviparous or cloacal.
The name “cloacae” is associated with the peculiarities internal structure of these animals: the intestines and genitourinary system flow into the cloaca and do not exit through separate channels to the outside. This fact confirms that monotreme mammals combine the characteristics of reptiles, amphibians and birds. In addition, representatives of the subclass are the only mammals that reproduce by laying eggs. However, due to feeding their young with milk, oviparous animals are classified as mammals.
The stomach is similar to a bird's crop and plays the role of food storage. The digestion process itself occurs in the intestines. Representatives of the subclass do not have vocal cords and are voiceless.
Female echidnas and platypuses do not have nipples. Milk is secreted through the tubular mammary glands. The cubs lick it from the fur of the mother's belly.
Classification of monotremes
Modern oviparous mammals are divided into two families:
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- Platypus - platypus;
- Echidnas - Australian echidna and echidnas.
Ancient fossils of monotremes are quite rare. The few existing recorded Mesozoic indurations suggest that oviparous organisms originally evolved in Australia and were distributed in South America and Antarctica, which used to be a single continent. Nowadays, representatives of the subclass are found only in Australia, on the island of Tasmania and New Guinea.
Oviparous animals initially separated from other mammals and developed in parallel and independently of them. Platypuses appeared earlier than echidnas, which adapted to a terrestrial lifestyle.
Rice. 1. Classification of the order “Monotreme mammals”.
This animal seems to be assembled from parts of other animals:
- nose - duck beak;
- tail like a beaver;
- paws - webbed, similar to flippers, equipped with powerful claws, used for digging.
The animal hunts at night for small crustaceans and mollusks. They are helped to find prey by electroreceptors on their leathery beak, which pick up the smallest impulses during the movement of the prey.
During the day, platypuses sleep in a hole near a pond. Animals cannot tolerate loud sounds and noise, so they stay away from civilization, preferring the wild.
Rice. 2. Platypus.
Echidnas
Being a relative of the platypus, the echidna swims and dives well, but does not know how to hunt underwater. Distinctive feature of these animals is a brood pouch on the belly where the egg is placed. The echidna lives on the ground and feeds on termites and ants. The body is densely covered with long needles; in case of danger, it curls up into a ball, like a hedgehog.
General characteristics of the order monotremes oviparous (Monotremata). Description of the history of discovery and appearance of the platypus. Features of the animal's organ system and metabolism, nutrition and reproduction. Study of the echidna family (Tachyglossidae).
monotreme monotremata platypus echidna
Introduction
Conclusion
List of sources
Introduction
First beasts (lat. Prototheria) are a subclass of primitive mammals that combine the features of mammals and reptiles. In this subclass, there is a single infraclass, Cloacae, opposed to the infraclasses Placentals and Marsupials from the subclass Beasts. Modern views The first animals are formed by only one order - monotremes.
First beasts are a small group of species common in the Australian region. Based on a number of characteristics, the subclass of proto-beasts and the infraclass cloacal are considered the most archaic and primitive among the infraclasses of mammals.
Unlike other mammals, primal animals reproduce by laying eggs, but more than half of the development period of the embryo passes in the female genital tract. Thus, the laid eggs contain an already sufficiently developed embryo and we can talk not only about oviposition, but also about incomplete viviparity.
Females, instead of nipples, have areas of mammary glands from which the offspring licks milk. There are no fleshy lips (effective for sucking). Moreover, like birds and reptiles, they have only one passage.
There is fur, but homeothermy (maintaining body temperature at a constant level) is incomplete; body temperature varies between 22-37°C.
Monotremes (lat. Monotremata), or oviparous (also sometimes cloacal) are the only modern order of the infraclass cloacal.
The name is due to the fact that the intestines and urogenital sinus flow into the cloaca (similarly in amphibians, reptiles and birds), and do not exit through separate passages.
According to paleontologist K.Yu. Eskov, the fact that the appearance of the first dinosaurs and other archosaurs was at one time marked by the massive (although not complete) extinction of therapsids, the highest forms of which in their organization were very close to monotreme mammals and, according to some assumptions, may have had milk, deserves attention. glands and wool. Nowadays, all types of cloacal insects live in Australia, New Guinea and Tasmania. Most species of this subclass are extinct. Oviparous monotremes known from fossils Cretaceous period And Cenozoic era, are currently represented by five cloacal species in two families (platypuses and echidnas) and one single order (monotremes).
According to paleontologist K.Yu. Eskov deserves attention to the fact that the appearance of archosaurs (a group of reptiles to which dinosaurs belong) coincided with the massive, but not complete, extinction of therapsids, the highest forms of which in their organization were very close to monotreme mammals, and, according to some assumptions, perhaps , had mammary glands and hair.
Fossil remains of representatives of the order Monotremes are known only from Australia. The most ancient finds date back to the Pleistocene and do not differ significantly from modern forms. There are two possible theories to explain the origin of monotremes. According to one of them, monotremes developed independently and in complete isolation from other mammals, starting from the early period of the emergence of mammals, possibly from their reptile-like ancestors. According to another theory, the group of monotremes separated from the ancient marsupials and acquired their features through specialization, retaining a number of characteristics characteristic of marsupials, and underwent degeneration and, perhaps, to a certain extent, a return to the forms of their ancestors (reversion). The first theory seems more plausible. Significant differences in morphology between echidnas and platypus arose over a relatively short period of time - starting in the Upper Eocene.
1. Characteristics of the order monotreme oviparous (Monotremata)
Monotremes are a small group of the most primitive living mammals. Females lay 1 or 2, rarely 3 eggs (characteristically have a high yolk content, the main mass of which is located at one of the poles of the egg). The hatching of the young from the eggs occurs with the help of a special egg “tooth” formed on a small ovoid bone. Young animals hatched from eggs and are fed milk. During the breeding season, a brood pouch may form on the female’s belly, in which the laid egg matures.
The sizes of monotremes are small: body length 30-80 cm. They have a heavy build, short plantigrade limbs, specialized for digging or swimming. The head is small, with an elongated “beak” covered with a cornea. The eyes are small, the external ears are barely noticeable or absent altogether. The body is covered with coarse hair and spines or soft, thick fur. Vibrissae are absent. In the heel region of the hind limbs there is a horny spur, especially strongly developed in males. The spur is pierced by a canal - a special duct connected to the so-called tibia gland, the function of which is not entirely clear. Apparently it has some significance in reproduction. There is also an assumption (unconvincing) that the secretion of the shin gland is poisonous and the spur serves as a weapon of defense. The mammary glands are tubular. There are no real nipples and the excretory ducts of the glands open separately from each other on the two glandular fields of the female’s abdomen.
The average body temperature is lower than that of other mammals (the platypus averages 32.2°C, the echidna - 31.1°C). Body temperature can vary between 25° and 36°C. The bladder, into which the ureters empty, opens into the cloaca. The oviducts empty into the cloaca separately (there is neither a vagina nor a uterus). The testes are located in the abdominal cavity. The penis is attached to the ventral wall of the cloaca and serves only to remove sperm.
The skull is flattened. The facial region is elongated. The cartilaginous skull and the relationship of bones in the roof of the skull are to a certain extent similar to those of reptiles. Roof of the skull with anterior and posterior frontal bones; the presence of these bones in the roof of the skull is a unique occurrence among mammals. The tympanic bone has the appearance of a flattened ring that does not fuse with the skull. The bony auditory canal is absent. The malleus and incus in the middle ear are fused together and have a long process (processus folii). The lacrimal bone is absent. The zygomatic bone is greatly reduced in size or absent. Only monotremes among all mammals have a prevomer. The premaxillary bone has a process similar to that of reptiles (processus ascendus); this is the only case among mammals. The articular fossa for the lower jaw is formed by the squamosal bone. The lower jaw has only two weakly defined processes - the coronoid and the angular.
Only young animals have teeth or are completely absent. The shape of the teeth to a certain extent resembles the shape of the teeth of the Mesozoic Microleptidae. The skeleton of the forelimb girdle is characterized by a coracoid (coracoideum) and a procoracoid (procoracoideum) that are unique among mammals. The presence of these bones reveals the similarity of the shoulder girdle of monotremes with the shoulder girdle of reptiles. Sternum with large episternum. The collarbone is very large. Blade without ridge. The humerus is short and powerful. The ulna is significantly longer than the radius. The wrist is short and wide. The fore and hind limbs are five-fingered. The fingers end in claws. In the pelvic girdle of males and females there are so-called marsupial bones (ossa marsupialia), articulated with the pubis. Their function is unclear. The symphysis of the pelvic bones is greatly elongated. Proximal fibula with a large flattened process (peronecranon).
The spinal column consists of 7 cervical, 15-17 thoracic, 2-3 lumbar, 2 sacral, 0-2 coccygeal and 11-20 caudal vertebrae (Fig. 1).
Rice. 1. Platypus skeleton
The entire body is covered with a highly developed layer of subcutaneous muscles (rap-niculus carnosus). Only in the area of the head, tail, limbs, cloaca and mammary glands, the subcutaneous muscles are not developed. The lower jaw has a musculus detrahens attached to it inside; this is the only case in mammals. The larynx is primitive and does not have vocal cords.
The brain is generally large, has the structural features of a mammal, but retains a number of reptilian characteristics. Large hemispheres with numerous, sometimes few, grooves. The structure of the cerebral cortex is primitive. The olfactory lobes are very large. The cerebellum is only partially covered by the cerebral hemispheres. The corpus callosum is absent; it is presented only in the form of commissura dorsalis. The sense of smell is highly developed. The Jacobson organ is well developed. The structure of the hearing organs is primitive. Eyes with or without nictitating membrane. The sclera has cartilage. The choroid is thin. Musculus dilatatorius and Musculus ciliaris are absent. The retina has no blood vessels.
The brain of platypuses is devoid of grooves and convolutions and, in terms of functional organization, resembles the brain of an echidna. Motor and sensory projections do not overlap throughout, while visual and auditory projections in the occipital pole of the cortex overlap with each other and partially with the somatic projection. This organization of the platypus neocortex, approaching the cortical plate of reptiles, allows it to be considered even more primitive in comparison with echidnas.
Consequently, the brain of monotremes still retains many features of the brain of reptiles and at the same time differs from the latter in the general plan of structure characteristic of mammals.
Salivary glands are small or large. The stomach is simple, without digestive glands, which is the only case in mammals. Its function appears to be to store food, similar to that of the crop of birds. The digestive tract is divided into small and large intestines, and there is a cecum. The intestines open into the cloaca, which is present in both sexes. The liver is multilobular, with a gall bladder. The heart of monotremes has a structure characteristic of mammals, but it also retains some reptile-like features, such as, for example, the fact that the right atrioventricular foramen is equipped with only one valve.
Monotremes live in forests different types, in the steppes overgrown with bushes, on the plains and in the mountains, rising to 2.5 thousand m above sea level. They lead a semi-aquatic (platypus) or terrestrial (echidnas) lifestyle; twilight and nocturnal activity; feed on insects and aquatic invertebrates. Life expectancy is up to 30 years. Distributed in Australia, Tasmania, New Guinea.
In comparison with all other modern mammals, modern monotremes are most similar to reptiles in their characteristics. They, however, are not the ancestors of marsupials or placental mammals, but represent a separate specialized branch in the evolution of mammals. Fossil remains of representatives of the order Monotremes are known only from Australia. The most ancient finds date back to the Pleistocene and do not differ significantly from modern forms. There are two possible theories to explain the origin of monotremes. According to one of them, monotremes developed independently and in complete isolation from other mammals, starting from the early period of the emergence of mammals, possibly from their reptile-like ancestors. According to another theory, the group of monotremes separated from the ancient marsupials and acquired their features through specialization, retaining a number of characteristics characteristic of marsupials, and underwent degeneration and, perhaps, to a certain extent, a return to the forms of their ancestors (reversion). The first theory seems more plausible. Significant differences in morphology between echidnas and platypus arose over a relatively short period of time - starting in the Upper Eocene. Echidnas are secondarily terrestrial mammals that separated from the ancient aquatic platypuses.
2. Platypus family (Ornithorhynchidae)
The platypus was discovered in the 18th century. during the colonization of New South Wales. A list of the colony's animals published in 1802 mentions "an amphibian animal of the genus of moles. Its most curious quality is that it has a duck's beak instead of an ordinary mouth, allowing it to feed in the mud like birds."
The first platypus skin was sent to England in 1797. Its appearance gave rise to fierce debate among the scientific community. At first, the skin was considered the product of some taxidermist who had sewn a duck's beak to the skin of an animal similar to a beaver. George Shaw managed to dispel this suspicion, who examined the parcel and came to the conclusion that it was not a fake (for this, Shaw even cut the skin in search of stitches). The question arose as to which group of animals the platypus belongs to. After he received his scientific name, the first animals were brought to England, and it turned out that the female platypus does not have visible mammary glands, but this animal, like birds, has a cloaca. For a quarter of a century, scientists could not decide where to classify the platypus - to mammals, birds, reptiles, or even to a separate class, until in 1824 the German biologist Meckel discovered that the platypus still has mammary glands and the female feeds her young with milk. The fact that the platypus lays eggs was proven only in 1884.
The zoological name for this strange animal was given in 1799 by the English naturalist George Shaw - Platypus anatinus, from ancient Greek. rlbfet (wide, flat) and rpet (paw) and lat. anatinus, "duck". In 1800, Johann-Friedrich Blumenbach, in order to avoid homonymy with the genus of bark beetles Platypus, changed the generic name to Ornithorhynchus, from the ancient Greek. ?snyt "bird", ?egchpt "beak". Aboriginal Australians knew the platypus by many names, including mallangong, boondaburra and tambreet. Early European settlers called it duckbill, duckmole, and watermole. Currently in English language the name platypus is used.
Appearance
The body length of the platypus is 30-40 cm, the tail is 10-15 cm, and it weighs up to 2 kg. Males are about a third larger than females. The body of the platypus is squat, short-legged; the tail is flattened, similar to the tail of a beaver, but covered with hair, which noticeably thins with age. In the tail of the platypus, like the Tasmanian devil, reserves of fat are deposited. Its fur is thick, soft, usually dark brown on the back and reddish or gray on the belly. The head is round. In front, the facial section is extended into a flat beak about 65 mm long and 50 mm wide (Fig. 2). The beak is not hard like that of birds, but soft, covered with elastic bare skin, which is stretched over two thin, long, arched bones.
The oral cavity is expanded into cheek pouches, in which food is stored during feeding. Down at the base of the beak, males have a specific gland that produces a secretion with a musky odor. Young platypuses have 8 teeth, but they are fragile and quickly wear out, giving way to keratinized plates.
The platypus has five-fingered feet, adapted for both swimming and digging. The swimming membrane on the front paws protrudes in front of the toes, but can bend in such a way that the claws are exposed, turning the swimming limb into a digging limb. The membranes on the hind legs are much less developed; For swimming, the platypus does not use its hind legs, like other semi-aquatic animals, but its front legs. The hind legs act as a rudder in the water, and the tail serves as a stabilizer. The gait of the platypus on land is more reminiscent of the gait of a reptile - it places its legs on the sides of the body.
Its nasal openings open on the upper side of its beak. There are no auricles. The eyes and ear openings are located in grooves on the sides of the head. When an animal dives, the edges of these grooves, like the valves of the nostrils, close, so that under water its vision, hearing, and smell are ineffective. However, the skin of the beak is rich in nerve endings, and this provides the platypus not only with a highly developed sense of touch, but also with the ability to electrolocate. Electroreceptors in the beak can detect weak electrical fields, which arise, for example, when the muscles of crustaceans contract, which helps the platypus in searching for prey. Looking for it, the platypus continuously moves its head from side to side during underwater hunting.
Organ systems
The platypus is the only mammal with developed electroreception. Electroreceptors have also been found in the echidna, but its use of electroreception is unlikely to play a role important role in search of prey.
Features of metabolism
The platypus has a remarkably low metabolism compared to other mammals; his normal body temperature is only 32°C. However, at the same time, he is excellent at regulating body temperature. Thus, being in water at 5°C, the platypus can maintain normal temperature body by increasing the metabolic rate by more than 3 times.
Platypus poison
The platypus is one of the few venomous mammals (along with some shrews and sawtooths, which have toxic saliva).
Young platypuses of both sexes have rudiments of horn spurs on their hind legs. In females, by the age of one year, they fall off, while in males they continue to grow, reaching 1.2-1.5 cm in length by the time of puberty. Each spur is connected by a duct to the femoral gland, which during the mating season produces a complex "cocktail" of poisons. Males use spurs during mating fights. Platypus venom can kill dingoes or other small animals. For humans, it is generally not fatal, but it causes very severe pain, and swelling develops at the injection site, which gradually spreads to the entire limb. Pain (hyperalgesia) can last for many days or even months.
Other oviparous - echidnas - also have rudimentary spurs on their hind legs, but they are not developed and are not poisonous.
Reproductive system
The reproductive system of the male platypus is normal for mammals, except that his testicles are located inside the body, near the kidneys, and there is also a bifurcated (many-headed) penis, common in most primitive mammals of the monotreme order (platypus, echidna) and marsupial order (possum, koala and others).
The female reproductive system differs from that of placental animals. Its paired ovaries are similar to those of a bird or reptile; Only the left one functions; the right one is underdeveloped and does not produce eggs.
Determination of gender
In 2004, scientists from the Australian National University in Canberra discovered that the platypus has 10 sex chromosomes, rather than two (XY) like most mammals. Accordingly, the combination XXXXXXXXXXX produces a female and XYXYXYXYXY produces a male. All sex chromosomes are linked into a single complex, which behaves as a single unit in meiosis. Therefore, males produce sperm with chains XXXXX and YYYYY. When sperm XXXXX fertilizes an egg, female platypuses are born, if sperm YYYYY, male platypuses are born. Although the platypus chromosome X1 has 11 genes that are found on all X chromosomes in mammals, and chromosome X5 has a gene called DMRT1 found on the Z chromosome in birds, being a key sex-determining gene in birds, overall genomic studies have shown that five sex The X chromosome of the platypus is homologous to the Z chromosome of birds. The platypus does not have the SRY gene (a key gene for sex determination in mammals); it is characterized by incomplete dosage compensation, recently described in birds. Apparently, the mechanism for determining the sex of the platypus is similar to that of its reptilian ancestors.
Lifestyle and nutrition
The platypus is a secretive, nocturnal, semi-aquatic animal that inhabits the banks of small rivers and standing ponds in eastern Australia over a wide range from the cold plateaus of Tasmania and the Australian Alps to the rainforests of coastal Queensland. In the north, its range reaches the Cape York Peninsula (Cooktown). Less is known about the distribution of the platypus inland. It appears to have completely disappeared from South Australia (except Kangaroo Island) and most of the Murray-Darling River basin. The reason for this was probably water pollution, to which the platypus is very sensitive. It prefers a water temperature of 25-29.9°C; V brackish water does not occur.
The platypus lives along the banks of reservoirs. Its shelter is a short straight hole (up to 10 m long), with two entrances and an internal chamber. One entrance is underwater, the other is located 1.2-3.6 m above the water level, under tree roots or in thickets.
The platypus is an excellent swimmer and diver, remaining underwater for up to 5 minutes. He spends up to 10 hours a day in water, since he needs to eat up to a quarter of his own weight in food per day. The platypus is active at night and at dusk. It feeds on small aquatic animals, stirring up the silt at the bottom of the reservoir with its beak and catching living creatures that have risen. They observed how the platypus, while feeding, turns over stones with its claws or with the help of its beak. It eats crustaceans, worms, insect larvae; less often tadpoles, mollusks and aquatic vegetation. Having collected food in its cheek pouches, the platypus rises to the surface and, lying on the water, grinds it with its horny jaws.
In nature, the platypus' enemies are few in number. Occasionally, he is attacked by a monitor lizard, a python, and a leopard seal swimming into the rivers.
Reproduction
Every year, platypuses go into a 5-10 day period. hibernation, after which they begin the breeding season. It lasts from August to November. Mating occurs in water. The male bites the female’s tail, and the animals swim in a circle for some time, after which mating occurs (in addition, 4 more variants of the courtship ritual have been recorded). The male covers several females; Platypuses do not form permanent pairs.
After mating, the female digs a brood hole. Unlike a regular burrow, it is longer and ends with a nesting chamber. A nest of stems and leaves is built inside; The female wears the material with her tail pressed to her stomach. Then she seals the corridor with one or more earthen plugs 15-20 cm thick to protect the hole from predators and floods. The female makes plugs with the help of her tail, which she uses like a mason uses a trowel. The inside of the nest is always moist, which prevents the eggs from drying out. The male does not take part in building the burrow and raising the young.
2 weeks after mating, the female lays 1-3 (usually 2) eggs. Platypus eggs are similar to reptile eggs - they are round, small (11 mm in diameter) and covered with an off-white leathery shell. After laying, the eggs stick together with an adhesive substance that covers them on the outside. Incubation lasts up to 10 days; During incubation, the female rarely leaves the burrow and usually lies curled up around the eggs.
Platypus cubs are born naked and blind, approximately 2.5 cm long. The female, lying on her back, moves them to her belly. She doesn't have a pouch. The mother feeds the cubs with milk, which comes out through the enlarged pores on her stomach. Milk flows down the mother's fur, accumulating in special grooves, and the cubs lick it off. The mother leaves the offspring only for short time to feed and dry the hide; leaving, she clogs the entrance with soil. The eyes of the cubs open at 11 weeks. Milk feeding lasts up to 4 months; at 17 weeks, the cubs begin to leave the hole to hunt. Young platypuses reach sexual maturity at the age of 1 year.
The lifespan of platypuses in nature is unknown; in captivity, they live an average of 10 years.
Population status and protection
Platypuses were previously hunted for their valuable fur, but at the beginning of the 20th century. hunting them was prohibited. Currently, their population is considered relatively stable, although due to water pollution and habitat degradation, the platypus' range is becoming increasingly patchy. It was also caused some damage by the rabbits brought by the colonists, who, by digging holes, disturbed the platypuses, forcing them to leave their habitable places.
Australians have created a special system of nature reserves and “sanctuaries” where platypuses can feel safe. Among them, the most famous are Healesville Nature Reserve in Victoria and West Burleigh in Queensland.
Evolution of the platypus
Monotremes are the surviving members of one of the earliest mammalian lineages. The age of the oldest monotreme discovered in Australia is 110 million years (Steropodon). It was a small, rodent-like animal that was nocturnal and, most likely, did not lay eggs, but gave birth to severely underdeveloped cubs. A fossilized tooth from another fossil platypus (Obdurodon), found in 1991 in Patagonia (Argentina), indicates that the platypus' ancestors most likely came to Australia from South America when these continents were part of the Gondwana supercontinent. The closest ancestors of the modern platypus appeared about 4.5 million years ago, while the earliest fossil specimen of Ornithorhynchus anatinus itself dates back to the Pleistocene. Fossil platypuses resembled modern ones, but were smaller in size.
In May 2008, it was announced that the platypus genome had been deciphered.
3. Echidna family (Tachyglossidae)
European scientists first learned about the echidna in 1792, when a member of the Royal Zoological Society in London, George Shaw (the same one who described the platypus a few years later), wrote a description of this animal, mistakenly classifying it as an anteater. The fact is that this amazing nosy creature was caught on an anthill. The scientist did not have any other information about the biology of the animal. Ten years later, Shaw's compatriot, anatomist Edward Home, discovered one common feature in the echidna and the platypus - both of these animals have only one hole at the back leading to the cloaca. And the intestines, ureters, and genital tracts open into it. Based on this feature, the order of monotremes (Monotremata) was identified.
Appearance
Echidnas look like a small porcupine, as they are covered with coarse hair and quills. The maximum body length is approximately 30 cm (Fig. 3). Their lips are beak-shaped. The echidna's limbs are short and quite strong, with large claws, thanks to which they can dig well. The echidna has no teeth and a small mouth. The basis of the diet is termites and ants, which echidnas catch with their long sticky tongue, as well as other small invertebrates, which echidnas crush in their mouths, pressing their tongues to the roof of their mouth.
The echidna's head is covered with coarse hair; The neck is short, almost invisible from the outside. The ears are not visible. The echidna's muzzle is elongated into a narrow "beak" 75 mm long, straight or slightly curved. It is an adaptation to searching for prey in narrow crevices and burrows, from where the echidna reaches it with its long sticky tongue. The mouth opening at the end of the beak is toothless and very small; it does not open wider than 5 mm. Like the platypus, the echidna's "beak" is richly innervated. Its skin contains both mechanoreceptors and special electroreceptor cells; with their help, the echidna detects weak fluctuations in the electric field that occur during the movement of small animals. No such electrolocation organ has been found in any mammal, other than the echidna and the platypus.
Muscular system
The echidna's musculature is quite peculiar. Thus, a special muscle panniculus carnosus, located under the skin and covering the entire body, allows the echidna to curl into a ball when in danger, hiding its stomach and exposing its spines. The echidna's muzzle and tongue muscles are highly specialized. Her tongue can protrude 18 cm from her mouth (its full length reaches 25 cm). It is covered with mucus to which ants and termites stick. Protrusion of the tongue is ensured by contraction of the orbicularis muscles, which change its shape and push it forward, and two geniohyoid muscles, which are attached to the root of the tongue and lower jaw. The protruding tongue becomes stiffer due to the rapid flow of blood. Its retraction is ensured by two longitudinal muscles. The tongue is capable of moving at high speed - up to 100 movements per minute.
Nervous system
In echidnas poor vision However, the sense of smell and hearing are well developed. Their ears are sensitive to low-frequency sounds, which allows them to hear termites and ants under the soil. The echidna's brain is better developed than that of the platypus and has more convolutions.
Until recently, it was believed that the echidna was the only mammal that does not dream. However, in February 2000, scientists from the University of Tasmania found that the sleeping echidna goes through a phase of paradoxical sleep, but it depends on the ambient temperature. At 25°C, the echidna exhibited a GFD phase, but as the temperature increased or decreased, it shortened or disappeared.
Lifestyle and nutrition
This is a terrestrial animal, although if necessary it is capable of swimming and crossing fairly large bodies of water. The echidna is found in any landscape that provides it with enough food - from moist forests to dry bush and even deserts. It is found in mountainous areas, where there is snow part of the year, on agricultural lands, and even in the suburbs of the capital. The echidna is active mainly during the day, but hot weather forces it to switch to a nocturnal lifestyle. The echidna is poorly adapted to heat, since it does not have sweat glands, and its body temperature is very low - 30-32°C. When it's hot or cold weather she becomes lethargic; when it gets very cold, it goes into hibernation for up to 4 months. Subcutaneous fat reserves allow her to fast for a month or more if necessary.
The echidna feeds on ants, termites, and less often other insects, small mollusks and worms. She digs up anthills and termite mounds, digs with her nose into the forest floor, strips the bark from fallen rotten trees, moves and turns over stones. Having discovered insects, the echidna throws out its long sticky tongue, to which the prey sticks. The echidna has no teeth, but at the root of the tongue there are keratin teeth that rub against the comb palate and thus grind food. In addition, the echidna, like birds, swallows earth, sand and small pebbles, which complete the grinding of food in the stomach.
The echidna leads a solitary lifestyle (except during the mating season). This is not a territorial animal - echidnas that meet simply ignore each other; it does not make permanent burrows and nests. The echidna rests in any convenient place - under roots, stones, in hollows fallen trees. The echidna runs poorly. Its main defense is thorns; the disturbed echidna curls up into a ball, like a hedgehog, and if it has time, it partially buries itself in the ground, exposing its back to the enemy with its needles raised. It is very difficult to pull an echidna out of a dug hole, since it strongly rests on its paws and spines. Predators that hunt echidnas include Tasmanian devils, as well as cats, foxes and dogs introduced by people. People rarely pursue it, since the skin of the echidna is not valuable, and the meat is not particularly tasty. The sounds that an alarmed echidna makes resemble a quiet grunt.
Echidnas are home to one of the largest fleas, Bradiopsylla echidnae, which reaches a length of 4 mm.
Reproduction
Echidnas live so secretly that their features marital behavior and breeding data were only published in 2003, after 12 years of field observations. It turned out that during the courtship period, which lasts from May to September (in different parts range, the time of its onset varies), these animals keep in groups consisting of a female and several males. Both females and males at this time emit a strong musky odor, allowing them to find each other. The group feeds and rests together; When crossing, echidnas follow in single file, forming a “train” or caravan. The female walks ahead, followed by males, of which there may be 7-10. Courtship lasts up to 4 weeks. When the female is ready to mate, she lies down, and the males begin to circle around her, throwing lumps of earth aside. After some time, a real trench with a depth of 18-25 cm is formed around the female. The males violently push each other, pushing them out of the trench, until only one winning male remains inside the ring. If there was only one male, the trench is straight. Mating (on the side) lasts about an hour.
Pregnancy lasts 21-28 days. The female builds a brood burrow, a warm, dry chamber often dug under an empty anthill, termite mound, or even under a pile of garden debris near human habitation. Typically, a clutch contains one leathery egg with a diameter of 13-17 mm and weighing only 1.5 g.
For a long time, it remained a mystery how the echidna moves the egg from the cloaca to the brood pouch - its mouth is too small for this, and its paws are clumsy.
Presumably, when putting it aside, the echidna deftly curls up into a ball; in this case, the skin on the abdomen forms a fold that secretes sticky liquid. When frozen, she glues the egg that has rolled out onto her stomach and at the same time gives the bag its shape (Fig. 4).
Brood pouch of a female echidna
After 10 days, a tiny baby hatches: it is 15 mm long and weighs only 0.4-0.5 g. Upon hatching, it breaks the shell of the egg with the help of a horny bump on the nose, an analogue of the egg tooth of birds and reptiles. The eyes of a newborn echidna are hidden under the skin, and the hind legs are practically undeveloped. But the front paws already have well-defined toes. With their help, in about 4 hours a newborn moves from the back of the pouch to the front, where there is a special area of skin called the milk field, or areola. In this area, 100-150 pores of the mammary glands open; each pore is equipped with a modified hair. When the cub squeezes these hairs with his mouth, milk enters his stomach. The high iron content gives echidna milk its pink color.
Young echidnas grow very quickly, increasing their weight by 800-1000 times in just two months, that is, up to 400 g. The cub remains in the mother's pouch for 50-55 days - until the age when it develops spines. After this, the mother leaves him in the shelter and until the age of 5-6 months comes to feed him once every 5-10 days. In total, milk feeding lasts 200 days. Between 180 and 240 days of life, the young echidna leaves the burrow and begins to lead independent life. Sexual maturity occurs at 2-3 years. The echidna reproduces only once every two years or less; according to some data - once every 3-7 years. But its low reproduction rate is compensated by its long life expectancy. In nature, the echidna lives up to 16 years; The recorded longevity record at the zoo is 45 years.
Population status and protection
Echidnas tolerate captivity well, but do not reproduce. Get offspring Australian echidna succeeded in only five zoos, but in none of the cases did the young live to adulthood.
Conclusion
Since 1798, disputes between zoologists in England, France and Germany have not subsided. There was some debate as to where these “one-hole animals,” or, in scientific terms, monotremes, should be placed in the taxonomy. This special subclass of mammals consists of only two families - echidnas and platypuses, representatives of which are found only in Eastern Australia, New Guinea and Tasmania. Even the fossil remains of their extinct ancestors have never been discovered anywhere else.
The names of these animals, which, with the light hand of the British, came into use in all countries, with scientific point the views are incorrect: the echidna is quite known species eels, and therefore it would be more correct to call it a duck-billed hedgehog; The British call the platypus platypus, while in everything scientific world It is known that one species of beetle was named this way back in 1793. The Germans often call the platypus and echidna sewer animals, which is especially tactless because it suggests some supposed uncleanliness of these animals or their affinity for sewers. Meanwhile, this name means only one thing: in these animals, the intestines and genitourinary canal do not open outward with independent openings (as in other mammals), but, like in reptiles and birds, they flow into the so-called cloaca, which communicates with the outside environment through one opening. So an unappetizing name should under no circumstances scare anyone away or make them think of latrines. On the contrary, these animals are very clean: if they settle near human habitation, they do not live in polluted rivers, but only in reservoirs with clean drinking water.
Today, neither platypuses nor echidnas are considered endangered or endangered. These animals have almost no natural enemies; only a carpet python, a fox or marsupial devil. Some platypuses die in the tops of fishermen: they swim there, but no longer find a way out, so they cannot go up for the necessary portion of air and suffocate. Until now, it has not been possible to convince fishermen to use tops with a hole at the top.
However, since 1905, platypuses have been under the full protection of the Australian state and have since reproduced quite successfully. They are found up to an altitude of 1650 meters above sea level. Most of them are in Tasmania. There, platypuses are found even in the suburbs of the capital, Hobart. Zoologist Sharland believes that intricate labyrinths of platypuses with nesting chambers can be found even under the streets of the suburbs. But one should not think that it is so easy for any strolling summer resident to see a platypus - one must not forget that this is a very cautious animal, leading a predominantly nocturnal lifestyle.
List of sources
1. Bram A.E. Animal life: In 3 vols. T. 1: Mammals. - M.: TERRA, 1992. - 524 p.
2. Gilyarov M.S. etc. Biological encyclopedic Dictionary, M., ed. Soviet Encyclopedia, 1989.
3. Klevezal G.A. Principles and methods for determining the age of mammals, M.: Partnership scientific. ed. KMK, 2007. - 283 p.
4. Lopatin I.K. Zoogeography. - Minsk: Higher School. 1989. - 318 p. ISBN 5-339-00144-X
5. Pavlinov I.Ya. Systematics of modern mammals. - M.: From Moscow University. 2003. - 297 p. ISSN 0134-8647
6. Pavlinov I.Ya., Kruskop S.V., Varshavsky A.A. and etc. Terrestrial mammals Russia. - M.: From KMK. 2002. - 298s. ISBN 5-87317-094-0
7. http://www.zooclub.ru/wild/perv/2.shtml
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Subclass of the First Beast (Prototheria)
Order Monotremes, or Oviparous (Monotremata) (E. V. Rogachev)
Monotremes (or oviparous) are the most primitive among modern mammals, retaining a number of archaic structural features inherited from reptiles (laying eggs, the presence of a well-developed coracoid bone not connected to the scapula, some details of the articulation of the skull bones, etc.). The development of their so-called marsupial bones (small pelvic bones) is also considered as a heritage of reptiles.
The presence of distinct coracoid bones distinguishes monotremes from marsupials and other mammals, in which this bone has become a simple outgrowth of the scapula. At the same time, hair and mammary glands are two interrelated characteristics characteristic of mammals. However, the mammary glands of oviparous animals are primitive and similar in structure to the sweat glands, while the mammary glands of marsupials and higher mammals are grape-shaped and similar to the sebaceous glands.
Quite a few similarities between monotremes and birds are adaptive rather than genetic. The laying of eggs by these animals brings monotremes closer to reptiles than to birds. However, in the egg, the yolk of monotremes is much less developed than that of birds. The keratinized egg shell is composed of keratin and also resembles the shell of reptile eggs. Birds are also reminiscent of such structural features as some reduction of the right ovary, the presence of pockets in the digestive tract resembling a bird's crop, and the absence of an external ear. However, these similarities are rather adaptive in nature and do not give the right to talk about any direct relationship between monotremes and birds.
Adult oviparous animals have no teeth. In 1888, milk teeth were discovered in a baby platypus, which disappear in an adult animal; these teeth are varied in structure, like those of higher mammals, and the two largest teeth on each jaw have the location and appearance of molars. In terms of body temperature, monotremes occupy an intermediate position between poikilotherms (reptiles) and true warm-blooded animals (mammals and birds). The body temperature of the echidna fluctuates around 30°, and that of the platypus - about 25°. But these are only average numbers: they change depending on the temperature external environment. Thus, the body temperature of an echidna increases by 4-6° when the environmental temperature changes from +5° to +30° C.
Currently, the order of monotremes has 5 living representatives belonging to two families: the platypus and 4 species of echidnas. All of them are distributed only in Australia, New Guinea and Tasmania (Map 1).
Family Platypuses (Ornithorhynchidae)
The only representative of the family is platypus(Ornithorhynchus anatinus) - was discovered at the very end of the 18th century. during the colonization period of New South Wales. In a list of animals of this colony published in 1802, the platypus was first mentioned as “an amphibian animal of the genus of moles... Its most curious quality is that it has a duck’s beak instead of an ordinary mouth, allowing it to feed in the mud like birds. ..". It was also noted that this animal digs a hole for itself with its claws. In 1799 Shaw and Nodder gave it a zoological name. European colonists called it "platypus", "duck mole", "water mole". Currently, Australians call it "platypus" (Fig. 14).
The very first scientific description of the platypus marked the beginning of fierce debate. It seemed paradoxical that a furry mammal could have a duck's beak and webbed feet. The first platypus skins brought to Europe were considered a fake, the product of skilled eastern taxidermists who deceived gullible European sailors. When this suspicion dissipated, the question arose as to which group of animals to classify him in. The "secrets" of the platypus continued to be revealed: in 1824, Meckel discovered that the platypus has glands that secrete milk. It was suspected that this animal laid eggs, but this was proven only in 1884.
The platypus is a brown-furred animal, about 65 cm long, including the length of its flattened tail, similar to that of a beaver. The head ends in the famous "duck beak", which is actually just an extended beak-shaped snout covered with a special kind of skin rich in nerves. This “beak” of the platypus is a tactile organ that also serves for obtaining food.
The platypus's head is round and smooth, and there is no external ear. The front feet are heavily webbed, but the membrane, which serves the animal when swimming, folds when the platypus walks on land or if it needs claws for digging holes. The membranes on the hind legs are much less developed. The main role in digging and swimming is played by the front legs, the hind legs have great importance when moving on land.
The platypus usually spends about two hours a day in water. He feeds twice: early in the morning and in the evening twilight. He spends most of his time in his hole, on land.
The platypus feeds on small aquatic animals. It stirs up the silt at the bottom of the reservoir with its beak and catches insects, crustaceans, worms and mollusks. Underwater he feels free, if, of course, there is an opportunity to catch his breath on the surface from time to time. Diving and rummaging in the mud, he is guided mainly by touch; His ears and eyes are protected by fur. On land, the platypus, in addition to touch, is guided by sight and hearing (Fig. 15).
Platypus burrows are located outside the water, including the entrance, located somewhere under the overhanging shore at a height of 1.2-3.6 m above water level. Only an exceptionally high flood can flood the entrance to such a hole. An ordinary hole is a semicircular cave dug under the roots of trees, with two or more entrances.
Every year, the platypus enters a short winter hibernation, after which it begins the breeding season. Males and females meet in the water. The male grabs the female's tail with his beak, and both animals swim in a circle for some time, after which mating occurs.
When the time comes for the female to lay eggs, she digs a special hole. First, he digs a gallery in the slope of the bank with a length of 4.5 to 6 m, at a depth of approximately 40 cm below the soil surface. At the end of this gallery, the female digs out the nesting chamber. In the water, the female searches for material for the nest, which she then brings into the hole with the help of her tenacious tail. She builds a nest from aquatic plants, willow twigs or eucalyptus leaves. Material too hard expectant mother grinds thoroughly. Then she clogs the entrance to the corridor with one or more earthen plugs, each 15-20 cm; It makes plugs with the help of its tail, which it uses like a mason's spatula. Traces of this work can always be seen on the tail of female platypus, which in its upper part is shabby and hairless. Thus, the female seals herself in a dark shelter inaccessible to predators. Even a person could not reveal the secret of her nesting shelter for a long time. Having completed this painstaking and complex work, the female lays eggs.
The first time a platypus laid eggs was observed in 1884 by Caldwell in Queensland. She was then traced to Healesville Game Reserve in Victoria. These eggs are small (less than 2 cm in diameter), round, surrounded by a dirty white shell, consisting not of lime, like in birds, but of a soft, elastic horn-like substance, so that they can easily become deformed. Usually there are two eggs in a nest, sometimes one, three or even four.
The duration of incubation may vary. Famous expert Australian animals David Flay found that incubation in the platypus does not exceed 10 days, and can last only a week, provided that the mother is in the nest. During incubation, the female lies, bending in a special way, and holds the eggs on her body.
The mammary glands of the platypus, discovered by Meckel in 1824, do not have a nipple and open outward with simple enlarged pores. From them, milk flows down the mother's fur, and the cubs lick it off. They grow quickly. During their feeding, the mother also feeds heavily; There is a known case where a nursing female ate earthworms and crustaceans overnight in quantities almost equal to her own weight.
The cubs are blind for 11 weeks, then their eyes open, but they continue to remain in the hole for another 6 weeks. These young, which feed only on milk, have teeth; As the animal grows, the milk teeth disappear and are replaced by simple horny plates. Only after 4 months do young platypuses go out on their first short excursion into the water, where they begin to clumsily search for food. Transfer from dairy nutrition progresses towards adulthood gradually. Platypuses are well tamed and live up to 10 years of age in captivity.
Platypuses are found in Queensland, New South Wales, Victoria, parts of South Australia and Tasmania. They are currently most abundant in Tasmania (Map 1).
The platypus is little picky about the composition of the water in which it searches for food. It tolerates both cold and clear waters mountain streams of the Australian Blue Mountains, both warm and muddy waters rivers and lakes of Queensland.
Quaternary remains of the platypus have been found in southern Queensland. Fossil platypuses resembled modern ones, but were smaller in size.
Before human migration to Australia, the platypus' enemies were few in number. Occasionally he was attacked only monitor lizard(Varanus varius), python(Python variegatus) and a seal swimming into the river leopard seal. The rabbits brought by the colonists created a dangerous situation for him. By burrowing, rabbits disturbed the platypus everywhere, and in many areas it disappeared, giving way to their territory. European settlers also pursued the platypus for its pelt. Many animals fell into traps set along the banks of the rivers for rabbits, and into the tops of fishermen.
Wherever people destroyed or disturbed the platypus, the surviving animals left these places. Where the man did not bother him, the platypus perfectly endured the neighborhood with him. To ensure the existence of the platypus, the Australians created a system of nature reserves and “refuges”, among which the most famous are Healesville Nature Reserve in Victoria and West Burleigh Nature Reserve in Queensland.
The platypus is an easily excitable, nervous animal. According to D. Fley, the sound of a voice or footsteps, some unusual noise or vibration, is enough for the platypus to be out of balance for many days, or even weeks. Therefore, for a long time it was not possible to transport platypuses to zoos in other countries. In 1922, the first platypus ever seen in other countries arrived at the New York Zoo; here he lived only 49 days; Every day for an hour it was shown to the public. Transportation became possible thanks to G. Burrell, who invented an artificial dwelling for the platypus, consisting of a reservoir of water (reservoir), a sloping labyrinth imitating a hole with rubber “soil,” and a supply of worms to feed the animal. To show the animal to the public, the wire cover of the living chamber of the platypus burrow was dislodged.
Platypuses were brought to the same zoo in New York twice: in 1947 and 1958. These transportations were organized by D. Flay. In 1947, three platypuses were transported to New York by sea; one of them died after 6 months, and the other two lived in the zoo for 10 years. In 1958, three more platypuses were flown to New York.
Echidna family (Tachyglossidae)
The second family of the monotreme order includes echidnas, covered with quills, like porcupines, but reminiscent of anteaters in their feeding type. The size of these animals usually does not exceed 40 cm. The body is covered with needles, the length of which can reach 6 cm. The color of the needles varies from white to black. Under the needles the body is covered with short brown hair. The echidna has a thin, pointed snout 5 cm, ending in a narrow mouth. Longer tufts of hair are usually developed around the ears. The tail is almost not expressed, there is only something like a projection from behind, covered with needles (Table 2).
There are currently 2 genera of echidnas: the echidna itself(genus Tachyglossus) living in Australia, and New Guinea echidnas(genus Proechidna). In the genus Tachyglossus, 2 species are distinguished: Australian echidna(T. aculeatus), one of the subspecies of which is endemic to New Guinea, and Tasmanian echidna(T. se~ tosus), distinguished by its larger size and thick hair, from which sparse and short needles protrude. The difference in the fur of these animals is probably due to the colder and humid climate Tasmania.
The echidna is found in Australia, in the eastern half of the continent and on its western tip, in Tasmania and New Guinea. The Tasmanian echidna is found in Tasmania and several islands in the Bass Strait.
The discovery of the echidna early in the colonization of New South Wales did not immediately receive the attention it deserved. In 1792, Shaw and Nodder described the Australian echidna and named it Echidna aculeata. In the same year, a Tasmanian species was discovered, described by Geoffroy as Echidna setosa. The echidna is a purely terrestrial animal. It lives in dry bush (brush thickets), preferring rocky areas. She doesn't dig holes. Its main defense is needles. When disturbed, the echidna curls up into a ball, like a hedgehog. With the help of its claws, it can partially burrow into loose soil; burying the front part of the body, she exposes the enemy only to needles directed backwards. During the day, hiding in the voids under roots, stones or in hollows, the echidna rests. At night she goes in search of insects. In cold weather, she remains in her den, falling into a short hibernation, like our hedgehogs. Subcutaneous fat reserves allow her to fast for a month or more if necessary.
The echidna's brain is more developed than that of the platypus. She has very fine hearing, but poor eyesight: she sees only the closest objects. During its excursions, mostly at night, this animal is guided mainly by its sense of smell.
Echidna feeds on ants, termites and other insects, and sometimes other small animals (earthworms, etc.). She destroys anthills, moves stones, pushing them with her paws, even rather heavy ones, under which worms and insects hide.
The strength of the echidna's muscles is amazing for an animal of such a small size. There is a story about a zoologist who locked an echidna in his kitchen for the night. The next morning he was very surprised to see that the echidna had moved all the furniture in the kitchen.
Having found an insect, the echidna throws out its thin, long and sticky tongue, to which the prey sticks.
The echidna has no teeth at all stages of its development, but on the back of its tongue there are horny teeth that rub against the pectinate palate and grind the caught insects. With the help of the tongue, the echidna swallows not only insects, but also earth and detritus, which, getting into the stomach, complete the grinding of food, similar to how it happens in the stomach of birds.
Like the platypus, the echidna incubates the eggs and feeds the young with milk. A single egg is placed in a primitive pouch, which is formed by the breeding season (Fig. 16). How the egg gets into the bag is still unknown. G. Burrell proved that the echidna cannot do this with the help of its paws, and put forward another hypothesis: its body is flexible enough so that, by bending, the female can lay an egg directly into the abdominal pouch. One way or another, the egg is “hatched” in this pouch, where it hatches into a baby. To get out of the egg, the baby breaks the shell using a horny bump on its nose.
Then he sticks his head into the hairy sac where the mammary glands open, and licks the milky secretions from the hairs of this sac. The baby stays in the pouch for quite a long time until its quills begin to develop. Then the mother leaves him in some shelter, but for some time she visits him and feeds him milk.
The echidna tolerates captivity well if it has protection from excess sun, from which it suffers greatly. She happily drinks milk, eats eggs and other food that can fit in her narrow, tube-like mouth. Her favorite treat is raw eggs, the shells of which have a hole punched into them where the echidna can stick her tongue. Some echidnas lived up to 27 years in captivity.
Aborigines, who loved to feast on echidna fat, often hunted it, and in Queensland they even specially trained dingoes to hunt echidnas.
Prochidna(genus Proechidna) are found in New Guinea. From Australian echidnas they are distinguished by a longer and curved snout (“beak”) and high three-fingered limbs, as well as small external ears (Fig. 17). Two now extinct species of echidna are known from the Quaternary, but this group is unknown from older deposits. The origin of echidnas is as mysterious as that of the platypus.
