home

Characteristics of the order monotreme oviparous (Monotremata). Oviparous mammal: description, features, reproduction and types. Order Monotremes or Oviparous. Characteristics and origin Types of monotremes

Oviparous - belong to the class mammals, subclass cloacal. Among all known vertebrates, monotremes are the most primitive mammals. The detachment received its name due to the presence of a special characteristic among its representatives. Oviparous animals have not yet adapted to viviparity and lay eggs to reproduce offspring, and after the babies are born, they feed them with milk.

Biologists believe that monotremes emerged from reptiles, as an offshoot from a group of mammals, even before the birth of marsupials and placentals.

The platypus is a representative oviparous species

Structure of the skeleton of the limbs, head, organs circulatory system, the breath of primal beasts and reptiles is similar. Fossils from the Mesozoic era have revealed remains of oviparous animals. Monotremes then inhabited the territory of Australia, and later occupied the South American expanses and Antarctica.

Today, the first beast can be found only in Australia and the islands located nearby.

Origin and diversity of mammals. Oviparous and true animals.

The ancestors of mammals are the reptiles of the Paleozoic. This fact confirms the similarity in the structure of reptiles and mammals, especially at the stages of embryogenesis.

In the Permian period, a group of theriodonts formed - the ancestors of modern mammals. Their teeth were placed in the recesses of the jaw. Most animals had a bony palate.

However, the environmental conditions that formed during the Mesozoic era contributed to the development of reptiles and they became the dominant group of animals. But the Mesozoic climate soon changed dramatically and reptiles were unable to adapt to new conditions, and mammals occupied the main niche of the animal world.

The class of mammals is divided into 2 subclasses:

Subclass Primordial or Monotreme;
subclass Real animals.

Real animals and monotremes share a number of characteristics: a hairy or spiny outer covering, mammary glands, and a hard palate. Also, primal beasts have common characteristics with reptiles and birds: the presence of a cloaca, laying eggs, and a similar skeletal structure.

Order Monotremes - general characteristics

Echidna is a representative of monotremes

Oviparous animals are not large sizes with a body flattened from top to bottom, short limbs with large claws and a leathery beak. They have small eyes and a short tail. Oviparous animals do not have a developed external auricle.

Only representatives of the duckbill family have teeth and they look like flat plates equipped with protrusions along the edges. The stomach is intended only for storing food; the intestines are responsible for digesting food. Salivary glands very developed, large in size, the stomach passes into the cecum, which, together with the urogenital sinus, flows into the cloaca.

First beasts do not have a real uterus and placenta. Reproduction by laying eggs, they contain little yolk, and the shell contains keratin. The mammary glands have many ducts that open on the ventral side in special glandular fields, since monotremes do not have nipples.

Body temperature can vary: it does not rise above 36°C, but with significant cold weather it can drop to 25°C. Echidnas and platypuses do not make sounds because they lack vocal cords. The lifespan of echidnas is about 30 years, platypuses - about 10. They inhabit forests, steppes with shrubs and are even found in mountainous areas (at an altitude of up to 2500m).

Representatives of oviparous species have poisonous glands. On the hind limbs there is a bone spur through which a poisonous secretion flows. The poison is potent, in many animals it provokes disruption of the functioning of vital organs, and it is also dangerous for humans - it causes severe pain and extensive swelling at the site of the lesion.

Catching and hunting for representatives of the detachment is prohibited, as they are listed in the Red Book due to the threat of extinction.

Platypus and Echidna

The platypus and echidna are oviparous mammals, the only representatives of the order.

A small animal about 30-40cm long (body), tail part up to 15cm, weighing 2kg. Males are always larger than females. It lives near bodies of water.

The five-fingered limbs are well adapted for digging the ground; on the coast, platypuses dig holes for themselves about 10 meters in length, arranging them for further life (one entrance is underwater, the other is a couple of meters above the water level). The head is equipped with a beak, like a duck’s (hence the name of the animal).

Platypuses stay in the water for 10 hours, where they obtain food: aquatic vegetation, worms, crustaceans and mollusks. Swimming membranes between the toes on the front paws (almost undeveloped on the hind limbs) allow the platypus to swim well and quickly. When the animal dives underwater, the eyes and ear openings close, but the platypus can navigate the water thanks to the sensitive nerve endings on its beak. It even has electroreception.

Platypuses carry their young for a month and produce from one to three eggs. First, the female incubates them for 10 days, and then feeds them with milk for about 4 months, and at the age of 5 months, the platypuses, already capable of independent life, leave the hole.

Oviparous mammals also include echidna, found in forests, similar in appearance to a hedgehog. To obtain food, the echidna digs the ground with powerful claws and, with the help of a long and sticky tongue, obtains the necessary food (termites, ants).

The body is covered with spines, which protect it from predators; when danger approaches, the echidna curls up into a ball and becomes inaccessible to enemies. The female weighs approximately 5 kg, and lays an egg weighing 2 g. The echidna hides the egg in a pouch formed by a leathery fold in the abdominal area and carries it, warming it with its warmth, for two weeks. A newborn calf is born with a weight of 0.5 g and continues to live in the mother’s pouch, where it is fed with milk.

After 1.5 months, the echidna leaves the pouch, but continues to live in the hole under the protection of its mother. After 7-8 months, the baby is able to find food on his own and differs from an adult only in size.

Amazing organisms that lay eggs and feed their young with milk are monotreme mammals. In our article we will look at the systematics and features of the life activity of this class of animals.

General characteristics of the class Mammals

The class Mammals, or Animals, includes the most highly organized representatives of the Chordata type. Their characteristic feature is the presence of mammary glands in females, the secretion of which they feed their young. The external features of their structure include the location of the limbs under the body, the presence of hair and various derivatives of the skin: nails, claws, horns, hooves.

Most mammals are also characterized by the presence of seven cervical vertebrae, a diaphragm, exclusively atmospheric breathing, a four-chambered heart, and the presence of a cortex in the brain.

Monotremes, marsupials, insectivores: the origin of Mammals

Mammals have significant species diversity. Platypus, kangaroo, mole, dolphin, whale, monkey, man - all these are representatives of this class. All of them originated from ancient reptiles. Proof of this fact is the similarity of their embryonic development, the presence of a cloaca and crow bones in some representatives, and the laying of eggs.

As a result of evolutionary processes and further divergence, orders of mammals arose: monotremes, marsupials, insectivores. The origin of mammals, as well as their subsequent development, has led to the fact that at present this class occupies a dominant position in the system of the animal world. Its representatives have mastered both land-air and aquatic habitats.

Subclass of the Prime Beast

This subclass of Mammals includes a single order called Monotremes. They received this name due to the presence of a cloaca. This is one hole into which the ducts of the reproductive, digestive and urinary systems open. All reproduce by laying eggs.

How can animals with such features be members of the class Mammals? The answer is simple. They have mammary glands that open directly onto the surface of the body, since monotremes do not have nipples. Newborns lick it directly from the skin.

Primitive structural features inherited from reptiles are the absence of cortex and convolutions in the brain, as well as teeth, the function of which is performed by horny plates. In addition, their body temperature fluctuates within certain limits depending on its changes in the environment from +25 to +36 degrees. Such warm-bloodedness can be considered quite relative.

Oviposition of monotremes cannot be called real. It is often called an incomplete viviparity. The fact is that the eggs do not immediately come out of the animal’s genital ducts, but linger there for a certain time. During this period, the embryo develops by half. After emerging from the cloaca, monotremes incubate their eggs or carry them in a special leathery pouch.

Monotreme mammals: fossil species

Paleontological finds of monotremes are quite few. They belong to the Miocene, Upper and Middle Pleistocene eras. The oldest fossil of these animals is 123 million years old. Scientists have concluded that the fossil remains are practically no different from modern species. Monotreme mammals, whose representatives are endemic, live only in Australia and the adjacent islands: New Zealand, Guinea, Tasmania.

Echidnas

The primal beast is one that is represented by only a few species. The echidna is a monotreme mammal. Due to the fact that its body is covered with long, hard spines, this animal looks like a hedgehog. In case of danger, the echidna curls up into a ball, thus protecting itself from enemies. The body of the animal is about 80 cm long, its front part is elongated and forms a small proboscis. Echidnas are nocturnal predators. During the day they rest, and at dusk they go hunting. Therefore, their vision is poorly developed, which is compensated by an excellent sense of smell. Echidnas have burrowing limbs. Using them and their sticky tongue, they hunt for invertebrates in the soil. Females usually lay one egg, which they incubate in skin fold.

Prochidna

These are also representatives of the class Mammals, order Monotremes. They differ from their closest relatives, echidnas, by a more elongated proboscis, as well as the presence of three fingers instead of five. Their needles are shorter, most of them are hidden in the fur. But the limbs, on the contrary, are longer. Prochidnas are endemic to the island of New Guinea.

The diet of these monotremes is based on earthworms and beetles. Like echidnas, they catch them with a sticky long tongue, on which there are numerous small hooks.

Platypus

This animal seems to have borrowed its body parts from other representatives of this kingdom. The platypus is adapted to a semi-aquatic lifestyle. Its body is covered with dense thick hair. It is very tough and practically waterproof. This animal has the beak of a duck and the tail of a beaver. The fingers have swimming membranes and sharp claws. In males, horny spurs develop on the hind limbs, into which the ducts of the poisonous glands open. For humans, their secretion is not fatal, but can cause severe swelling, first of a certain area, and then of the entire limb.

This mammal hunts well in water. But it builds nests and burrows exclusively on land. This is not a harmless lie. It swims at considerable speed, and grabs prey almost at lightning speed - within 30 seconds. Therefore, aquatic animals have very little chance of escaping from a predator. Thanks to its valuable fur, the number of platypus has decreased significantly. At the moment, hunting them is prohibited.

Subclass Real animals

Monotreme mammals are primarily characterized by the presence of a cloaca. Real animals have separate openings for the digestive, reproductive and urinary systems. This subclass includes marsupials and placental mammals.

Order Marsupials

Representatives of this systematic unit have a leather pouch on their belly. Some monotreme mammals also have this structural feature. But in marsupials, the ducts of the mammary glands open into it. Most of these animals live in Australia, but the opossum is also found in North America.

The most famous representative of the order Marsupials is the kangaroo. This large mammal, which moves by jumping. Their length can reach up to 1.5 m. Thanks to their well-developed hind limbs and tail, they move very quickly. Kangaroos can reach speeds of up to 50 km/h. These herbivores are often attacked by various predators. They defend themselves with their hind limbs, supported by their tail.

Lives in southern Australia marsupial bear, which is also called the koala. This cute animal sits motionless in the trees all day. And at night it goes to active image life. The koala's diet consists of leaves and young shoots of eucalyptus. These animals are quite voracious. They can eat up to a kilogram of food per day. Koala meat is inedible, but the fur is of great value to humans. For this reason, this species was practically on the verge of extinction. At this time, this animal is listed in the International Red Book.

Marsupials have mastered several habitats. Most of them are terrestrial animals. Some live in trees. These are the koala and the marsupial flying squirrel. Some species live underground. These include the opossum.

Placental Mammals

And marsupials are dioecious animals with internal fertilization. The placental representatives of this class have the most progressive structural features. They are most widespread in nature. During embryonic development, a baby's place or placenta is formed. This is the organ that provides communication between the embryo and the mother’s body. The gestation period of placentals ranges from 11 days in mouse-like rodents to 24 months.

This group of mammals is represented by a large number of orders. Thus, representatives of insectivores are hedgehogs, moles, muskrats, shrews, and shrews. Their common feature is not only the nature of the food, but also the appearance. The anterior section of the head of insectivores is elongated and forms a short proboscis, on which there are sensitive hairs.

Placentals have mastered all habitats except the organismic one. Chiropterans are capable of flight due to the presence of a fold of skin between the fingers, which serves as their wing. Pinnipeds most They spend their lives in water, and Cetaceans live there constantly. Terrestrial placentals include Rodents, Lagomorphs, Pairs and Odd-toeds, Carnivores and Primates. The man represents the last squad.

Mammals - monotremes, marsupials and placentals feed their young with milk. Each of the listed superclasses has its own characteristic features. In monotremes, the cloaca is preserved; in marsupials, a skin fold is formed, in which the newborn develops for a certain period. All of them are endemic to Australia. Marsupials and monotremes do not have a placenta. Thanks to the presence of an organ that connects the body of mother and child during intrauterine development, completely viable individuals are born. Therefore, placentals are the most highly organized representatives of the class.

Lesson type - combined

Methods: partially search, problem presentation, reproductive, explanatory and illustrative.

Target: mastering the ability to apply biological knowledge in practical activities, use information about modern achievements in the field of biology; work with biological devices, instruments, reference books; conduct observations of biological objects;

Tasks:

Educational: formation cognitive culture, mastered in the process of educational activities, and aesthetic culture as the ability to have an emotional and value-based attitude towards objects of living nature.

Educational: development of cognitive motives aimed at obtaining new knowledge about living nature; cognitive qualities of a person associated with mastering the fundamentals of scientific knowledge, mastering methods of studying nature, and developing intellectual skills;

Educational: orientation in the system of moral norms and values: recognition of the high value of life in all its manifestations, the health of one’s own and other people; environmental consciousness; nurturing love for nature;

Personal: understanding of responsibility for the quality of acquired knowledge; understanding the value of adequately assessing one’s own achievements and capabilities;

Cognitive: ability to analyze and evaluate the impact of environmental factors, risk factors on health, the consequences of human activities in ecosystems, the impact of one’s own actions on living organisms and ecosystems; focus on continuous development and self-development; the ability to work with various sources of information, transform it from one form to another, compare and analyze information, draw conclusions, prepare messages and presentations.

Regulatory: the ability to organize independent completion of tasks, evaluate the correctness of work, and reflect on one’s activities.

Communicative: the formation of communicative competence in communication and cooperation with peers, understanding the characteristics of gender socialization in adolescence, socially useful, educational and research, creative and other types of activities.

Technologies : Health conservation, problem-based, developmental education, group activities

Types of activities (content elements, control)

Formation in students of activity abilities and abilities to structure and systematize the subject content being studied: collective work - study of text and illustrative material, compilation of a table “Systematic groups of multicellular organisms” with the advisory assistance of student experts, followed by self-test; pair or group performance of laboratory work with the advisory assistance of a teacher, followed by mutual testing; independent work on the studied material.

Planned results

Subject

understand the meaning of biological terms;

describe the structural features and basic life processes of animals of different systematic groups; compare the structural features of protozoa and multicellular animals;

recognize organs and organ systems of animals of different systematic groups; compare and explain reasons for similarities and differences;

establish the relationship between the structural features of organs and the functions they perform;

give examples of animals of different systematic groups;

distinguish the main systematic groups protozoa and multicellular animals;

characterize the directions of evolution of the animal world; provide evidence of the evolution of the animal world;

Metasubject UUD

Cognitive:

work with different sources of information, analyze and evaluate information, transform it from one form to another;

draw up theses, various types of plans (simple, complex, etc.), structure educational material, give definitions of concepts;

carry out observations, perform elementary experiments and explain the results obtained;

compare and classify, independently choosing criteria for the specified logical operations;

build logical reasoning, including establishing cause-and-effect relationships;

create schematic models highlighting the essential characteristics of objects;

identify possible sources of necessary information, search for information, analyze and evaluate its reliability;

Regulatory:

organize and plan your educational activities - determine the purpose of the work, the sequence of actions, set tasks, predict the results of the work;

independently put forward options for solving assigned tasks, anticipate the final results of the work, choose the means to achieve the goal;

work according to plan, compare your actions with the goal and, if necessary, correct mistakes yourself;

master the basics of self-control and self-assessment for making decisions and making informed choices in educational, cognitive and educational and practical activities;

Communicative:

listen and engage in dialogue, participate in collective discussion of problems;

integrate and build productive interactions with peers and adults;

adequately use verbal means for discussion and argumentation of one’s position, compare different points of view, argue one’s point of view, defend one’s position.

Personal UUD

Formation and development of cognitive interest in the study of biology and the history of the development of knowledge about nature

Techniques: analysis, synthesis, inference, translation of information from one type to another, generalization.

Basic Concepts

Diversity of mammals, division into orders; general characteristics of units, the relationship between lifestyle and external structure. The importance of mammals in nature and human life, the protection of mammals.

During the classes

Updating knowledge ( concentration when learning new material)

Choose the correct answer option in your opinion.

1. What is the common characteristic of all vertebrates?

presence of a spine

habitat in the air-terrestrial environment

multicellularity

2. How is the vertebrate brain protected?

sink

shell

skull

3. How many types of vertebrates are there?

4. Which one special body breathing in fish?

leather

5. What are the respiratory organs of amphibians?

lungs and skin

6. Which vertebrates first appeared on earth?

Reptiles

Amphibians

7. How do reptiles reproduce?

give birth to babies

lay eggs

lay eggs

8. Which one distinctive feature birds?

live in the air-terrestrial environment

body covered with feathers

only they lay eggs

9. Which group of vertebrates is the most organized on earth?

mammals

10. How do mammals differ from other vertebrates?

feed the young with milk

breathe with their lungs

warm-blooded

Learning new material(teacher's story with elements of conversation)

Monotreme mammals: general characteristics, features and origin .

Amazing organisms that lay eggs and feed their young with milk are monotreme mammals. In our article we will look at the systematics and features of the life activity of this class of animals. general characteristics class Mammals.

Most mammals are also characterized by the presence of seven cervical vertebrae, a diaphragm, exclusively atmospheric breathing, a four-chambered heart, and the presence of a cortex in the brain

Subclass of the Prime Beast. This subclass of Mammals includes a single order called Monotremes. They received this name due to the presence of a cloaca. This is one hole into which the ducts of the reproductive, digestive and urinary systems open. All these animals reproduce by laying eggs. How can animals with such features be members of the class Mammals? The answer is simple. They have mammary glands that open directly onto the surface of the body, since monotremes do not have nipples. Newborns lick it directly from the skin. Primitive structural features inherited from reptiles are the absence of cortex and convolutions in the brain, as well as teeth, the function of which is performed by horny plates. In addition, their body temperature fluctuates within certain limits depending on its changes in the environment from +25 to +36 degrees. Such warm-bloodedness can be considered quite relative. Oviposition of monotremes cannot be called real. It is often called an incomplete viviparity. The fact is that the eggs do not immediately come out of the animal’s genital ducts, but linger there for a certain time. During this period, the embryo develops by half. After emerging from the cloaca, monotremes incubate their eggs or carry them in a special leathery pouch.

Monotreme mammals: fossil species Paleontological finds of monotremes are quite few in number. They belong to the Miocene, Upper and Middle Pleistocene eras. The oldest fossil of these animals is 123 million years old. Scientists have concluded that the fossil remains are practically no different from modern species. Monotreme mammals, whose representatives are endemic, live only in Australia and the adjacent islands: New Zealand, Guinea, Tasmania.

Echidna Prime Beasts- represented by only a few species. The echidna is a monotreme mammal. Due to the fact that its body is covered with long, hard spines, this animal looks like a hedgehog. In case of danger, the echidna curls up into a ball, thus protecting itself from enemies. The body of the animal is about 80 cm long, its front part is elongated and forms a small proboscis. Echidnas are nocturnal predators. During the day they rest, and at dusk they go hunting. Therefore, their vision is poorly developed, which is compensated by an excellent sense of smell. Echidnas have burrowing limbs. Using them and their sticky tongue, they hunt for invertebrates in the soil. Females usually lay one egg, which is incubated in a fold of skin.

Prochidna These are also representatives of the class Mammals, order Monotremes. They differ from their closest relatives, echidnas, by a more elongated proboscis, as well as the presence of three fingers instead of five. Their needles are shorter, most of them are hidden in the fur. But the limbs, on the contrary, are longer. Prochidnas are endemic to the island of New Guinea. The diet of these monotremes is based on earthworms and beetles. Like echidnas, they catch them with a sticky long tongue, on which there are numerous small hooks.

Platypus. This animal seems to have borrowed its body parts from other representatives of this kingdom. The platypus is adapted to a semi-aquatic lifestyle. Its body is covered with dense thick hair. It is very tough and practically waterproof. This animal has the beak of a duck and the tail of a beaver. The fingers have swimming membranes and sharp claws. In males, horny spurs develop on the hind limbs, into which the ducts of the poisonous glands open. For humans, their secretion is not fatal, but can cause severe swelling, first of a certain area, and then of the entire limb.

It’s not for nothing that the platypus is sometimes called “God’s joke.” According to legend, at the end of the creation of the world, the Creator had unused parts from various animals. From these he created the platypus. It's not just Australian endemic. This is one of the symbols of the continent, the image of which is found even on the coins of this state. This mammal hunts well in water. But it builds nests and burrows exclusively on land. It swims at considerable speed, and grabs prey almost at lightning speed - within 30 seconds. Therefore, aquatic animals have very little chance of escaping from a predator. Thanks to its valuable fur, the number of platypus has decreased significantly. At the moment, hunting them is prohibited.

V.V. Latyushin, E. A. Lamekhova. Biology. 7th grade. Workbook to the textbook V.V. Latyushina, V.A. Shapkina “Biology. Animals. 7th grade". - M.: Bustard.

Zakharova N. Yu. Control and testing work in biology: to the textbook by V.V. Latyushin and V.A. Shapkin “Biology. Animals. 7th grade” / N. Yu. Zakharova. 2nd ed. - M.: Publishing house "Exam"

Presentation hosting

It 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 tropical rainforests of coastal Queensland. In the north, its range reaches the Cape York Peninsula (Cooktown).

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. Fat reserves are deposited in the tail of the platypus. 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. 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.

Young platypuses of both sexes have the rudiments of horny spurs on their hind legs. In females, by the age of one year they fall off, but 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 produces a complex “cocktail” of poisons during the mating season. 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.

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.

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 babies are born naked and blind, approximately 2.5 cm long. When hatching from the egg, they pierce the shell with an egg tooth, which falls off immediately after leaving the egg. The female, lying on her back, moves them to her belly. She does not have a brood 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 a short time to feed and dry the skin; leaving, she clogs the entrance with soil. The cubs' eyes open at 11 weeks. Breastfeeding continues 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 the wild is unknown; in captivity they live an average of 10 years.

Bruina's echidna
Western Long-beaked Echidna
(Zaglossus bruijni)

The habitat of the echidna is the highlands of the northwestern part of New Guinea and the islands of Salawati and Waigeo (Indonesia). Habitat Its habitat is moist montane forests, although it is sometimes found in alpine meadows at altitudes of up to 4000 m above sea level.

Body length up to 77 cm and weight 5-10 kg. The most well-fed individuals weigh more than 16 kg. The tail is rudimentary, 5-7 cm in length. The limbs are higher than those of echidnas, with developed muscles and powerful claws. Males have horny spurs on the inner surface of their hind legs, similar to those of the platypus, but not poisonous. The hind limbs of the echidna are five-fingered, the front three-fingered. The beak (rostrum) of the prochidna occupies 2/3 of the length of the head and is strongly curved downwards; at its end there are nostrils and a small mouth. Small ears are visible on the head. The tongue of the echidna is very long (up to 30 cm) and covered with sharp spines that compensate for the lack of teeth. The body of the echidna is covered with coarse fur of a dark brown or black color; Short spines grow on the back and sides, almost hidden by fur. The color of the needles varies from almost white to black, length 3-5 cm.

The echidna's diet consists almost entirely of earthworms, which it searches for by digging its beak in the ground. Having caught a large worm, the echidna steps on it with its front paw, captures the tip of the worm in its mouth and, actively helping itself with its tongue, pulls it inside. In this case, the worm is impaled on the sharp spines of the tongue. Less commonly, echidnas eat termites, insect larvae, and possibly ants.

The echidna needs its beak not only to search for food. It turned out that this is an additional tenacious limb, allowing the animal to overcome obstacles or turn over stones as a lever. She moves rather slowly, with her head lowered to the ground. If a stone or log gets in the way of an echidna, it prefers to climb over it rather than go around it; a lake or puddle - swim across. If the echidna is frightened, it hides or crouches, tucking its beak under itself and exposing its spines.

Prochidnas are heterothermic animals; their temperature, depending on the ambient temperature, can vary from 36 to 25 °C. At the same time, echidnas continue to remain active and only under the most unfavorable conditions do they hibernate.

The breeding season for echidnas begins in July. After mating, the female lays one egg, which she places in her pouch. After about ten days, the egg hatches into a baby, which the female feeds with milk for up to 6 months.

The longest life expectancy recorded for an individual living at the London Zoo was 30 years and 8 months.

Barton's echidna
Eastern Long-beaked Echidna
(Zaglossus bartoni)

Distributed in the mountains of central and eastern New Guinea. It lives in tropical forests at an altitude of about 4100 m above sea level.

Body weight is 5-10 kg, body length is from 60 to 100 cm. Unlike other representatives of the genus, it has 5 claws on the forelimbs.

The genus (Zaglossus) also includes Attenborough's echidna (Zaglossus attenboroughi). This species is only known from a single specimen, which was found during the Dutch colonial period in 1961. Since then, no other copies have been found.

Australian echidna
Short-beaked Echidna
(Tachyglossus aculeatus)

It lives in Australia, Tasmania, New Guinea and the islands in Bass Strait.

The Australian echidna is smaller than the echidna: its usual length is 30-45 cm, weight from 2.5 to 5 kg. The Tasmanian subspecies is somewhat larger - up to 53 cm. 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.

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 rain 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 night look life. The echidna is poorly adapted to heat, since it does not have sweat glands, and its body temperature is very low - 30-32 °C. In hot or cold weather it becomes lethargic; when it gets very cold, it goes into hibernation for up to 4 months. Reserves subcutaneous fat allow her to fast for a month or more if necessary.

It feeds on ants, termites, and less commonly 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.

Echidnas live so secretly that their features mating 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 (the time of its onset varies in different parts of the range), 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 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. Freezing, she glues the egg that has rolled out onto her stomach and at the same time gives the bag its shape.

After 10 days, a tiny baby hatches - it is 15 mm long and weighs only 0.4-0.5 g. When hatching, the puggle 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 baby squeezes these hairs with its mouth, milk enters its 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.

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 species of primitive animals form 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 are known from Cretaceous fossils 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 were very close in their organization 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 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. Symphysis pelvic bones 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 its inner side; 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 according to plan 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 of various types, in steppes overgrown with bushes, on plains and in mountains, rising up 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 it received its 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.

Organ systems

Platypus - only mammal, having developed electroreception. Electroreceptors have also been found in the echidna, but its use of electroreception is unlikely to play an important role in searching for 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 body temperature for several hours by increasing its metabolic rate by more than 3 times.

Platypus poison

The platypus is one of the few venomous mammals (along with some shrews and gaptooths, which have toxic saliva).

Other oviparous animals - 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 common for mammals, except that the testicles are located inside the body, near the kidneys, and there is also a forked (multi-headed) penis, common in most primitive mammals of the monotreme order (platypus, echidna) and marsupial order (opossum, 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; not found in brackish water.

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 enter a 5-10-day winter hibernation, after which they enter 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.

Platypus cubs are born naked and blind, approximately 2.5 cm long. The female, lying on her back, moves them to her belly. She does not have a brood 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 a short time to feed and dry the skin; leaving, she clogs the entrance with soil. The cubs' eyes 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 the wild is unknown; in captivity they live an average of 10 years.

Population status and conservation

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 those continents formed part of the supercontinent Gondwanaland. 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 big-nosed 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 able to move with high speed- up to 100 movements per minute.

Nervous system

Echidnas have poor eyesight, but their 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 large quantity 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 wet 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. In hot or cold weather it 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 for 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 the hollows of 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 the peculiarities of their mating behavior and reproduction were published only in 2003, after 12 years of field observations. It turned out that during the courtship period, which lasts from May to September (the time of its onset varies in different parts of the range), 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 an 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 conservation

Echidnas tolerate captivity well, but do not reproduce. It was possible to obtain offspring of the Australian echidna only in 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 a fairly well-known species of eel, and therefore it would be more correct to call it a duck-billed hedgehog; The British call the platypus platypus, while throughout the scientific world it is known that this was the name given to one species of beetle 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. - 298 p. ISBN 5-87317-094-0

7. http://www.zooclub.ru/wild/perv/2.shtml

What else to read

Abstract: History of the development of hygiene 1. The development of hygiene in primitive and slave societies. The emergence and development of hygiene has a centuries-old history...

Formation of estimated liabilities and reserves for vacations As in 1s 8 Hello, dear blog readers. Lately, in my consulting work, I have quite often...

Puff khinkal in a pressure cooker Puff DAGESTAN KHINKAL Puff khinkal is often prepared in Dagestan. A very tasty, but high-calorie, masculine dish....

Characteristics of the order monotreme oviparous (Monotremata). Oviparous mammal: description, features, reproduction and types. Order Monotremes or Oviparous. Characteristics and origin Types of monotremes

Origin and diversity of mammals. Oviparous and true animals.

Order Monotremes - general characteristics

Platypus and Echidna

General characteristics of the class Mammals

Monotremes, marsupials, insectivores: the origin of Mammals

Subclass of the Prime Beast

Monotreme mammals: fossil species

Echidnas

Prochidna

Platypus

Subclass Real animals

Order Marsupials

Placental Mammals

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).

Similar documents

What else to read

THE LAST NOTES

Characteristics of the order monotreme oviparous (Monotremata). Oviparous mammal: description, features, reproduction and types. Order Monotremes or Oviparous. Characteristics and origin Types of monotremes

Origin and diversity of mammals. Oviparous and true animals.

Order Monotremes - general characteristics

Platypus and Echidna

General characteristics of the class Mammals

Monotremes, marsupials, insectivores: the origin of Mammals

Subclass of the Prime Beast

Monotreme mammals: fossil species

Echidnas

Prochidna

Platypus

Subclass Real animals

Order Marsupials

Placental Mammals

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).

Similar documents

What else to read

THE LAST NOTES

Categories