Let amphibians not be the most attractive and cute creatures. They're not kittens to please everyone. But among them there are also the most interesting rare individuals that can captivate anyone with their truly extravagant appearance. Let's get acquainted with this strange class of animals (these are neither on land nor on water - neither yours nor ours) and learn more about the most outstanding representatives.

Traits of amphibians: duplicity as a gift

Amphibians, also known as amphibians (translated from Greek means “one that lives double life") are those groups of animals that can live both on land and in water. Therefore, they stand out from all other living beings and have a number of advantages.

The main external sign of an amphibian is “nakedness” (they are devoid of fur or any other heat-insulating coverings). It is believed that the ancestors of amphibians were lobe-finned fish. But they themselves gave life to reptiles.

Types of amphibians: with or without a tail?

Scientists distinguish three types of amphibians based on the presence and development of the tail and paws.

Tailless amphibians

They have a short body, a poorly defined neck, developed legs (the hind legs are larger and more massive than the front ones: they are used for moving by jumping), and of course they do not have a tail. This species includes toads, frogs, tree frogs, spadefoots, toads and others. This is the largest order, which numbers about five thousand different species.

Tailed amphibians

They have a long body that ends in a strong, developed tail, but their legs are short and weak (although there are exceptions). Among the representatives of this order, the most noticeable are newts and salamanders. In total, the group numbers about five hundred species. And just some species of salamanders stand out from the general background - they can run rapidly and even jump.

Legless (aka worms)

They differ in that they have neither a tail nor paws - the animals are unlucky, they seem completely helpless! Moreover, they also look very unattractive - these amphibians look like nasty worms. And with scientific point vision have the most primitive structure of their kind.

Not only hypocrites, but also opportunists

Animals belonging to the class of amphibians are surprisingly tenacious - they live on all continents of the globe, except Antarctica. They are opportunists: very salty waters, arid territories and serious cold - they don’t mind any difficulties! If you climb into the Himalayas, you will meet an amphibian in the mountain heights.

And if you are carried into the desert or beyond the Arctic Circle (you never know what will happen for fun), then they are here too, just like underground.

True, these are rather exceptional options. The most fertile environment for amphibians is humid, warm and nourishing (where it is easy for amphibian animals to find edible prey) tropical countries.

Amphibians: the immortal snow queen

One of the rarest amphibians is the Siberian salamander. It has a unique cold resistance, which allows this amphibian to exist, in principle, in conditions not typical for its class - in the harsh north of Russia (the territory from the Urals to Kamchatka). And these are temperatures reaching 30-35 degrees below zero, and permafrost...

It is noteworthy that these creatures can survive even in ice for several years at a time. After geologists found such seemingly frozen to death individuals, they thawed, warmed up and returned to vigorous life. How can you come back to life after an icy death? The fact is that during frost, the water in the cells of this amphibian turns into glycerol, which protects them from certain death.

Rare amphibians: a frog that doesn't croak

But in the lowlands of the British mountains there lives a peculiar frog called the chicken frog. In addition to the fact that it belongs to the largest frog species in the world (reaches 21 centimeters), its meat also has an exceptional taste.

Actually, this is why the green amphibian of peculiar beauty was named that way. True, only criminally wealthy gourmets can now afford such a delicacy, because it is under the protection of the country as a species on the verge of extinction.

Fish that walks

Either a fish or a reptile - a very strange creature! Another unique member of the amphibian class with terrifying names is the water monster, the walking fish, and in science, the axolotl. He, too, can boast of unconventional beauty and strange qualities of survival.

The most remarkable of them is that these amphibians reach sexual maturity without entering the adult stage, but remaining a larva, sometimes even for life. They, as befits amphibians, can live both on land and in water. But often they do not “work” on the development of lungs, like other amphibians, but live in water spaces, but without the scales that fish rely on.

Take it for yourself and tell your friends!

Read also on our website:

show more

Amphibians, or amphibians, are the first terrestrial vertebrates that still retain significant connections with aquatic environment. Descended from lobe-fins in the Devonian. The only modern lobe-finned fish that is closest to the hypothetical ancestor is the coelacanth. In most species, eggs (spawn) lack dense shells and can only develop in water. The larvae hatching from eggs lead an aquatic lifestyle and only then undergo metamorphosis (transformation), during which the characteristics of adults leading a terrestrial lifestyle are formed.

Adult amphibians are characterized by paired limbs with articulated joints. The skull articulates movably with the cervical vertebra by two occipital condyles. The palatoquadrate cartilage fuses with the braincase (autostyle skull), and the upper element of the hyoid arch - the pendulum - turns into the bone of the middle ear - the stapes. The pelvic girdle is attached to the transverse processes of the sacral vertebra. Spine 4 sections (cervical - 1 vertebra, trunk, sacral - one vertebra, caudal - in tailless animals all vertebrae are fused into the urostyle. Two circles of blood circulation are formed, not completely separated: in the heart there are two atria, but one ventricle. The cerebellum is small. The eyes have movable eyelids are the main sensory organ. The middle ear appears (one auditory ossicle - the column and the tympanic membrane). The lateral line organs in adults usually disappear. The forebrain enlarges and is divided into two hemispheres; in its roof there are clusters of nerve cells. The average level of metabolism of amphibians is noticeable above the level of the fish, a mobile muscular tongue appears and salivary glands. Skin is permeable to water and gases; bare skin has a large number of multicellular mucous glands. There are lungs (ventilation due to changes in the volume of the oropharyngeal cavity), but the oropharyngeal cavity and integument are involved in breathing. A second circle of blood circulation appears, and mixed blood appears in the heart. The heart has three main chambers and five sections (venous sinus, two atria, ventricle, conus arteriosus. The excretory organs are the trunk (mesonephric) kidneys and skin. Body temperature depends on the ambient temperature and only slightly exceeds the latter (poikilothermia).

Orders of amphibians

The appearance of tailless amphibians is determined by the compactness of the body, which was achieved by the virtual disappearance of the neck and tail. All the caudal vertebrae grew together into one bone - the urostyle, and the total number of vertebrae decreased, which began to be firmly connected to each other. In most species, the length of the forelimbs is 30 - 61% of the hind limbs. The compactness of the body contributed to the acquisition of a jumping type of movement. In the jump of tailless amphibians, three phases are distinguished: rebound, “flight” and landing, the first and last of which last only 0.1 seconds.

Tailless squad. Photo: Brian Gratwicke

The rebound is associated with the elongation of the toes of the hind limb, the stretching of the two bones of the foot (tibidae and fibulare) with the formation of another (additional) lever - the tarsus or “secondary tibia”, the fusion of the tibia and fibula (tibula and filula) into a single tibia (crus) . To more effectively use the forces that allow one to lift off the ground, the points of their application are moved closer to each other (the pelvis narrows) and to the animal’s center of gravity (the iliac bones lengthen). Flight maneuverability is largely determined by the ability to make an “asymmetrical rebound” as a result of early lifting of one of the limbs from the ground, which allows you to change the direction of movement. The main load when landing in tailless amphibians falls on the humerus and ulna (radius and ulna), which are fused to give them strength. In order not to slip when touching the wet ground, articular tubercles have arisen on the lower surface of the paws, between the phalanges of the fingers, in many species of tailless amphibians. The ease of landing is associated with the relative shortening and reduction of the phalanges of the fingers on the forelimb compared to the hindlimb. All these transformations led to a fairly efficient method of transportation. Toads and frogs spend less than 2% of energy to overcome air resistance in “flight”. Modifications of the hind limb were also successful when moving in an aquatic environment. Strong lever legs, between the phalanges of which a swimming membrane is stretched, used as a rowing surface, allow rapid movement in the water column, with which most species do not lose contact due to cutaneous respiration. Movement in the water corresponds to the breaststroke style, but without the participation of the forelimbs. Tailless amphibians with shorter legs (toads, for example) move along the land surface at a walking pace. A number of changes occur in the skull of tailless amphibians, for example, the frontal and parietal bones fuse into one frontoparietal. The gill arches are transformed into the hyoid apparatus. In addition to the inner ear, the middle ear also appears, closed by the eardrum or, less commonly, by the skin. The circulatory system is characterized by the disappearance of the third arterial arch and the connection between the aortic arch, carotid and pulmonary arteries. If the ratio of the length of the capillaries of the skin to that of the lungs in the crested newt is 3:1, then even in moisture-loving tailless amphibians (spadefoots and toads) it changes to 1:1, in frogs - 1:2, and in relatively dry-loving toads it is already 1:3. At the same time, pulmonary respiration is not so perfect that cutaneous respiration can be abandoned, so saving moisture remains an important problem. It is partly solved by an aquatic (15% of species) or semi-aquatic way of life, partly by the significant development of subcutaneous lymphatic cavities (sacs) - reservoirs in which unfavorable conditions Water reserves may accumulate. Lymphatic lacunae occupy almost the entire subcutaneous space and only in a few bridges between the bags the skin is connected to the muscles by strips of connective tissue. U land species(for example, in toads) moisture loss reduces compaction and partial keratinization of the skin. All this made it possible to significantly increase survival rate during the development of various ecological niches of the land habitat. Adaptive behavior plays a huge role in water metabolism. Some amphibians choose wetter habitats. Other, relatively terrestrial forms chose for their life activities the cool twilight-night time, when more humidified air reduces moisture loss (aquatic frogs are active around the clock). Cloudy weather allows terrestrial species to hunt in daytime. They usually use places with high humidity as shelters (depressions between roots, under moss, hollows, rodent holes, etc.). The development of new environmental conditions, the peculiarities of activity and life on the land surface required the transformation of the nervous system and sensory organs. The brain of tailless amphibians is somewhat larger than the brain of tailed amphibians, they have an enlarged eyeball, the number of photoreceptor cells reaches 400 - 680 thousand, and their cones, unlike those of tailed amphibians, contain oil drops. Enlargement and shift of the eyes top surface head flattened in the dorso-ventral (dorso-ventral) direction allowed tailless amphibians to increase the total field of vision to 360? (with a significant angle of binocular vision, which made it possible for them to quite accurately determine the distance to a moving small food object. The eye of tailless amphibians sends partially processed information to the brain, from special ganglion clusters - retinal nerve cells (detectors). Five types of such have been identified in frogs detectors: dark field detector (responsible for reacting to a moving small object in a dark field), straight edge detector (helps to avoid obstacles), fast moving contrast object detector, darkness detector (responsible to slow changes in illumination) and darkening detector (assessing the nature of illumination) Only four types of detectors have been identified in toads, and grass frog(Rana temporaria) and bullfrog (Rana catesbiana) direction detectors were also discovered. Many tailless amphibians are good at distinguishing between blue, green and yellow colors. Based on the study of the mechanisms of their vision in tailless amphibians, special photographic devices have been created that make it possible to recognize small objects. Tailless amphibians have in effective ways perceive and produce sounds in both water and air environments. They can receive sound vibrations in the range from 30 to 15,000 Hz. In the laryngeal-tracheal system, tailless amphibians have vocal cords that produce species-specific sounds, the volume of which is amplified by throat sacs or external resonators - skin cavities in the corners of the mouth of males of some species that swell when croaking. Vocal reactions (so-called “songs”) of tailless amphibians play an important role in social communication and serve reproduction. Unlike tailed amphibians, a number of tailless amphibians are characterized by a “mating fast,” that is, a cessation of feeding during the breeding season. Fertilization in Anura is external (external). Only a few species have internal fertilization. Some tropical forms are characterized by viviparity (more precisely, ovoviviparity). However, in most cases, the eggs are laid in the water and fertilized by the male at the time of mating. Moreover, many males have nuptial calluses - rough, keratinized swellings of the skin on the forelimbs. The clutches have a variety of shapes (in the form of single eggs, cords of different lengths and thicknesses, lumps, etc.). The clumping of eggs into conglomerates makes it difficult for small predators to eat them, and the spherical shells of the eggs, swollen in water, play the role of collecting lenses that concentrate light rays, due to which the temperature inside the lump is 5 - 7 ° C higher than the ambient temperature. Many species have specific devices for protecting clutches ("nests", subcutaneous bags, etc.). The fertility of a number of species is very high; some frogs and toads lay up to 7,000 - 10,000 eggs. The eggs of tailless amphibians hatch into larvae (tadpoles) that have a tail, which disappears during metamorphosis. The hatched larvae have a special suction organ with which they attach to aquatic plants or empty egg shells. Their development usually takes place in an aquatic environment. The external gills of tadpoles are overgrown with a fold of skin; their communication with the external environment is carried out through the gill opening (spiraculum). The mouth opening is bordered by fringed lips, on them inner surface There are rows of horny denticles and jaws with which the tadpoles scrape food from underwater objects. The series of teeth in different species are arranged specifically, which is reflected in dental formulas and is used for diagnosis. Metamorphosis of tailless amphibians is accompanied by necrosis (destruction) of larval tissues and their replacement with structures characteristic of adult individuals. The population density of tadpoles and the maintenance of its genetic diversity (polymorphism) is regulated by larval metabolic products - metabolites, the number of which, for example, increases with increasing population size, which suppresses the growth of small individuals, increasing the rate of metamorphosis and the chances of survival of large larvae. Individuals coming onto land are called fingerlings. Tailless amphibians are the most numerous and diverse order of amphibians. This group of amphibians includes 4231 species and 335 genera, grouped into 24 families as of early 1996. The fauna of the former USSR contains 29 species from 6 genera and 6 families (almost 0.7% of the species diversity of the world fauna). And on the territory of Russia there live 22 species from the same number of genera and families as in former USSR. Tailless amphibians inhabit almost all land surfaces, except for the polar and a number of oceanic islands. In the mountains they rise to 5238 m, where at the foot of the glacier it was discovered the new kind green toad

There are relatively few tailed amphibians - about 340 species. All tailed amphibians are characterized by having an elongated body, which turns into a well-developed tail. The front legs have from 3 to 4, the hind legs from 2 to 5 toes. In some, the limbs have almost disappeared for the second time (amphiuma) or the back pair of them are completely absent (sirens). Most tailed animals crawl or swim, bending their bodies like snakes. Only a few terrestrial salamanders can run fast, like lizards, or even jump. When swimming, the limbs are pressed against the body and do not take part in the movement.

Detachment Tailed. Photo: Aah-Yeah

The shape of the body, the nature of movement, like many structural features of caudate amphibians, are “primitive and the least specialized for the class as a whole. Thus, caudates are characterized by biconcave (amphicoelous) or retroconcave (opisthocoelous) vertebrae, the number of which ranges from 36 to 98. In In lower forms, the rudimentary notochord remains throughout life.There are no real ribs, but there are short upper ribs, like in bony fish. The shoulder girdle for the most part remains cartilaginous, and the coracoids movably overlap one another; the collarbone is missing. The radius and ulna, tibia and fibula are not fused, as are the carpal and tarsal bones. In the pelvic girdle, the presence of prepubic cartilage is typical. The frontal and parietal bones of the skull are not fused, as in anurans. As a rule, there is no quadratojugal bone, so the posterior edge of the maxillary bone ends freely. In addition to the anterior ear, there may be 1-2 ear bones. At least three independent arches are always preserved in the hyoid apparatus. There is no tympanic cavity or tympanic membrane, which is a secondary phenomenon (primitive caudate amphibians retain remains of the tympanic cavity). The larvae of tailed amphibians have 4 pairs of gill slits, which disappear in most adults. Only the siren has 3 pairs, and the proteus and the well newt have 2 pairs of gill slits. The circulatory system in the lower groups of caudate amphibians is characterized by an incomplete septum between the atria and the absence of a longitudinal valve in the conus arteriosus. Higher caudate amphibians have a complete septum between the atria and a valve in the conus arteriosus, but many retain all four arterial arches, and in the venous system, along with the posterior vena cava, there are posterior cardinal veins that flow into the ducts of Cuvier. Most breathe through lungs, skin and mucous membranes oral cavity. Sometimes in adults the lungs disappear and gas exchange occurs only through the skin and oral mucosa; in connection with this it is being rebuilt circulatory system and the heart becomes two-chambered.

Fertilization in the vast majority of tailed amphibians is internal, and the female captures the mucous sacs with sperm (spermatophores) deposited by the males with the cloaca. The amount of eggs laid by tailed fish is relatively small - from 2-5 to 600-700 eggs. All species are characterized by care for their offspring, ranging from the simple case of wrapping eggs in the leaves of underwater plants and ending with the protection of egg clutches and viviparity. The transformation (metamorphosis) of larvae into an adult animal occurs gradually and is not accompanied by fundamental changes in organization. In a number of species, reproduction is observed in the larval stage (neoteny).

Currently living tailed amphibians are united into 54 genera, 8 families and 5 suborders.

The suborder Cryptobranchoidea contains the most primitive caudate amphibians, characterized by biconcave vertebrae, free angular bone, and external fertilization. This includes the families of cryptobranchidae (Cryptobranchidae) and angletooths (Hynobiidae).
The suborder Meantes contains one family of sirens (Sirenidae), characterized by 3 pairs of gills in adult animals.
The suborder Proteidea includes one family of proteas (Proteidae), which are neotenic larvae of unknown salamanders.
The suborder Ambystomatoidea also contains one big family Ambystomatidae, characterized by biconcave vertebrae and the absence of an angular bone. Neoteny is widely developed among Ambystomaceae.
The suborder Salamanclroiclea is the largest and contains the family (Amphiumidae), lungless salamanders (Plethodontidae) and true salamanders (Salamandridae). For most representatives of the suborder, the vertebrae are posterior-concave and the angular bone is fused with the articular bone.

A large number of suborders and families (with a relatively small number of species) is determined by the diverse organization of living tailed amphibians, which obviously have repeatedly changed their habitat over a long period of evolutionary development. The vast majority of species of tailed amphibians live permanently in water; about 200 species, 35 genera and 5 families are represented only by permanently aquatic forms. It should be added that many terrestrial species, such as the common newt, spend most of the summer in water bodies, and other terrestrial species, such as representatives of the genus Ambistoma, often have neotenic larvae (axolotls) that constantly live in the water. The more associated a species is with a body of water, the more elongated the animal’s body is, as a rule. long tail fin develops; the limbs, on the contrary, become smaller. However, species living in mountain streams, where the flow is fast, are distinguished by strong limbs, sometimes equipped with claws, such as, for example, the faceted clawed newt in Ussuri. In inhabitants of underground reservoirs, such as Proteus from the underground rivers of Yugoslavia, the pigment in the integument disappears and the eyes are reduced.

In contrast to aquatic tailed amphibians, few terrestrial species are characterized by a short body and long and powerful limbs. The running of some completely terrestrial cave salamanders is similar to the fast running of lizards. They are good at climbing rocks, trees and even jumping. Interestingly, these terrestrial species, like frogs, have a protruding tongue. Among the terrestrial tailed animals there are also underground species, for example the slender salamander, which has a serpentine body with very weak limbs.

Tailed amphibians are limited in their distribution almost exclusively to the northern hemisphere. So, in Australia there are no tailed animals at all. In Africa, where about 800 species of amphibians live, there are only 4 species of caudates, common in the north of the continent. Tailed amphibians almost do not penetrate into South Asia, and only into South America(and even in its northern mountainous part) several species of lungless salamanders live.

The first representatives of the caudate order were found in deposits of the Cretaceous period. Fossil remains of all major families are numerous from the Eocene alone. However, the antiquity of tailed amphibians is well proven by their geographical distribution. Thus, among them there are numerous cases of broken propagation; for example, one species of Protea lives in Europe, and another in North America; cryptobranchs live in Japan and China, as well as in North America. In addition, many tailed animals have extremely narrow ranges; for example, the Caucasian salamander lives only in Western Transcaucasia, the Semirechensky frogtooth - in the Dzungarian Alatau, the clawed newt - only in the Ussuri region and adjacent areas to the south. A lot of tailed amphibians, with extremely small distribution areas, live in Southwestern China. Thus, tailed amphibians live in northern and temperate latitudes (especially mountainous regions), where there are relatively few tailless amphibians, while the majority of tailed amphibians have switched to an aquatic lifestyle for the second time.

Legless amphibians are the smallest (165 species, grouped into 32 genera and 5 families) and the most primitive group of modern amphibians. Their fossil remains with vestigial limbs are described from the Lower Jurassic of Arizona, and typically legless forms (Apodos) are described from the Paleocene of Brazil. Like fish, legless amphibians retained biconcave (amphicoelous) vertebrae with well-developed notochord remnants between them.

Legless Squad. Photo: Rob and Stephanie Levy

Among other primitive features, experts note an incomplete septum between the atria, the articulation of the auditory ossicle with the quadrate bone, short lower ribs, the presence of bone scales in the skin of many representatives, etc. The bone scales of legless amphibians are specific formations secreted by two types of skin glands, located both in epithelial-connective tissue (mainly in Caecilia spp.), and in overgrown skin grooves, forming ring or semi-ring transverse rows, usually consisting of several (up to eight) scales. Their number in the body can reach 2000, and in the anterior part they are smaller (up to 1 - 2 mm) than in the posterior part (about 4 mm). In the most mobile areas of the body (in the tail area, for example), they are destroyed, leaving small cavities in the thickness of the skin. The most characteristic feature of legless amphibians is the worm-like (snake-like) body shape without a tail (which is expressed only in the most primitive forms), limbs and even their belts, and the body is divided into segments by constrictions. The ring segments are bounded by grooves, the edges of which are in contact with each other, forming cavities that stick together and become overgrown in some species. In some cases, one segment is located above one vertebra, however, in many species the number of rings does not correspond to the number of vertebrae, since the wide occipital rings (called the collar) account for 3-4 vertebrae, and the caudal segment, clearly visible when located only in front of the anus - 2 - 5. In species of the genera Epicrionops and Ichthyophis, the number of grooves is less than the number of vertebrae. Representatives of the genus Ichthyophis have segments that are not strictly vertical, but somewhat oblique, arching like a wedge on the upper side of the body. Many species of legless amphibians are characterized by secondary segmentation (the presence of one or more weaker grooves between the grooves of one segment). Some genera and family Typhlonectidae do not have them at all. The number of primary rings varies from 70 (in Grandisonia sp.) to 283 (in Caecilia sp.), and the sum of primary and secondary rings can reach 430. It is no coincidence that since the first mention of legless amphibians in 1735 by the famous zoologist and collector Albert Seba , for such a segmented body, similar to annelids, they are called caecilians. Many famous researchers of the past (Linnaeus, Laurenti, Latreille, Daudin, Rey), however, classified caecilians as snakes. Only in 1807 did Dumeril point out their relationship with frogs and toads, and Oppel in 1811 legitimized this view by giving them the name Apoda (from the Greek “a” - not, “podos” - leg). Some past researchers considered caecilians to be degenerate salamanders. The longest species is considered to be the gigantic caecilian (Caecilia thompsoni) - 1375 mm, and possibly up to 1.5 m, the width of its body is 92 times the length. The smallest legless amphibians are considered to be tiny and short caecilians - Idiocranium russeli, Grandisonia brevis. Their maximum sizes are 114 mm (the length exceeds the width on average by 25 times) and 112 mm (14 times), respectively, although many individuals are able to reproduce already with a body length of 5 mm. Caecilians lead a predominantly burrowing lifestyle, making passages in moist soil (although there are also aquatic forms), which left its mark not only on their appearance(absence of limbs and elongated body), but also the shape internal organs: the left lung has lengthened, and the right has shortened (as in snakes). Their kidneys have become narrow and ribbon-like, the number of vertebrae in a number of species reaches 200 - 300, the facial part of the skull, involved in digging holes, and the skin on the head are tightly fused with the skull, the nasal bone in many species has merged with the premaxillary, scaly with the square zygomatic, superior auricular and anterior auricular with lateral occipital and parasphenoid, the middle ear and tympanic membrane have disappeared (although caecilians are capable of perceiving sounds with a frequency of 100 to 1500 Hz). Their eyes were hidden under the skin or even under the bones (in Scoleocomorphus). In a number of caecilians, however, there are usually transparent “windows” above the eyes, and the retina contains only reduced optic rods without cones. Due to the loss of vision, their sense of smell and touch developed greatly. These functions in legless amphibians are performed by a special tentacle 2–3 mm long, noticeable only in adult specimens and located in a special pit of the skin. In addition, it is believed that the tentacle is able to sense the moisture, consistency and temperature of the substrate (soil). In this case, the caecilians feel underground objects first from the left side, and then from the right. The duct of the large ocular (also called garoere) gland opens into the tentacle fossa, the secretion of which in other vertebrates provides lubrication of the eye, although it was previously assumed to be poisonous. The tentacle of representatives of the family Scoleomorphidae is capable of pushing the eye through the opening of the tentacles in the skull from under the skull, placing it in this way above the skull. The underground lifestyle also affected the reproduction of caecilians. They are few of the amphibians that have internal fertilization: the male's cloaca, with special muscles, is everted from the hindgut and serves as a copulatory organ, the blood vessels of which, being saturated with blood, give it an elastic (erect) state. The form of such a copulative (copulative) apparatus is extremely species-specific. Row African births They even have spines on the cloaca. And some aquatic Potomotyphlus also have a specialized grasping organ in the anal region. In representatives of the genus Scoleocomorphus, the cloaca is surrounded by ridges. All these formations are absent in young organisms, and therefore suggest their participation in the reproduction of adult individuals, helping the male to hold the female during mating. In the cloaca of males, paired glands were found that play a role in stimulating reproduction, which, in the absence of sexual dimorphism, can be an important factor in successful mating of caecilians. In some aquatic forms, however, similarities were observed mating dance. During the breeding season, males accumulate fat in their bodies, due to which they thicken and become similar to the body shape of pregnant females. Thus, the width of the body of the same species may be different in different physiological states. Most caecilians lay up to 20 - 30 eggs in moist soil, crevices of the substrate near water, and many species protect the clutch, wrapping their body around it (caring for offspring). The abundant mucous secretions of the skin glands allow them not to dry out. Sometimes some caecilians attach eggs with threads in the form of a bunch of “balloons”. After hatching, the larvae migrate into the water and swim there for several months (up to a year). Another distinctive feature of the bream is the appearance during embryonic development of seven (not six) gill slits (seven slits are found only in some cartilaginous fish). The embryos of legless amphibians have external gills in the form of branched tufts (in Ichthyophis spp., Hypogeophis spp.) or plates (Typhlonectes spp., Siphonops spp.). The larvae have typically fishy lateral line organs and a dorsal fin (a fold 1–5 mm high), which disappears after metamorphosis. The exception is aquatic forms, in which the fin remains throughout its life. And some species have a larval fin on their belly. Their main hematopoietic organ is the liver, and not the bone marrow, as in adults. Viviparous species are also found among legless amphibians. These are, as a rule, aquatic forms (Typhlonectes spp.), producing 5 - 8 eggs. After fertilization, their eggs remain in the oviduct, where the developing embryos receive food not through blood, but as if scraping from the walls of the oviduct with larval teeth (not identical to the teeth of adult animals) the secretion of specific glands in the form of thick milk. Eating such high-calorie foods, fetuses gain weight very quickly. Pregnancy in caecilians lasts 9 - 11 months. Caecilians live in the tropics of America, Africa and Asia (they are not found only in Australia and Madagascar). Many species of legless amphibians are very rare, moreover, they are known from only a few specimens, their lifestyle is practically not studied. The bulk of legless amphibians are active at night. At rest, caecilians consume 4–6 times more oxygen than when moving. During the day they hide along the banks of reservoirs, which is why they get caught in fishermen’s nets. In Mexico, legless amphibians can often be found in stables in manure, where a significant number of dipteran insect larvae are concentrated. The main food items for caecilians are termites, earthworms, insect larvae and mollusks. Among the enemies of terrestrial caecilians, various snakes (in particular, coral snakes) and birds of prey (for example, fawn harrier) are usually called, and aquatic legless amphibians feed on fish, frogs, freshwater turtles and semi-aquatic mammals. When preparing the information, the following materials were used: Dunaev E. A., 1999. Diversity of amphibians. - M.: MSU.

(Amphibia), a class of terrestrial vertebrates (tetrapods). They occupy an intermediate position between fish and higher vertebrates. Amphibians evolved from ancient lobe-finned fish in the 2nd half of the Devonian (about 375 million years ago). The oldest amphibian is Ichthyostega, which reached a length of 1 m; had short limbs, a caudal fin, small bony scales in the skin of the tail, and rudiments of gill covers.

In the 1st half of the Carboniferous appeared diverse groups primitive amphibians - stegocephalians, which were divided into 2 main evolutionary trunks - labyrinthodonts and lepospondyls, differing in the structure of the teeth and spine. Among them were forms with well-developed limbs, adapted to life on land. The question of the origin of modern amphibians (they are combined into the group of lissamphibians, Lissamphibia) - from labyrinthodonts or from lepospondylic stegocephalians - remains debatable. Modern amphibians include more than 4,000 species belonging to three orders: anuran amphibians, legless amphibians and tailed amphibians. Fossil representatives of tailless amphibians are known from the Early Triassic, legless and tailed amphibians - from the Early and Middle Jurassic.

The organization of amphibians retains the characteristics inherited from fish, including low metabolic rate and variability in body temperature (determined by the temperature of the external environment). Amphibians have a more or less close relationship with the aquatic environment throughout their lives; their eggs (spawn) lack embryonic membranes, so development in the vast majority of amphibians occurs in water bodies.

The body length of amphibians ranges from less than 1.2 cm (for example, the Cuban dwarf, Sminthillus limbatus) to 150 cm or more (giant salamanders). The coloring is varied. The skin contains many glands; often their secretion can be toxic to other organisms. The skull (wide, low and flattened) is movably articulated with the spine by two occipital condyles. In the latter, there are cervical (with 1 vertebra), trunk, sacral and caudal sections. The ribs are short (do not reach the sternum), chest do not form. Most amphibians have limbs equipped with fingers and are adapted for terrestrial locomotion. The teeth have a so-called pedicellar (stalk-like) structure: they consist of a stalk-like base (pedicle) and a crown, connected by flexible, non-calcified dense connective tissue. The skeleton retains a lot of cartilage tissue.

The anterior part of the brain makes up about half of it total mass. The cerebellum is small. The organs of smell and touch are well developed. The ocular cornea is convex; the iris and ciliary body contain smooth muscles; accommodation of the eye is carried out by movements of the lens. Hearing in the air is developed only in tailless amphibians, which have not only an inner ear, but also a middle ear with a tympanic membrane. The tongue is mobile (has its own muscles); its glands secrete sticky mucus that helps capture small prey. In amphibians, salivary glands appear for the first time. Tailless amphibians are characterized by the ability to push a bolus of food from the mouth into the esophagus with the participation of the eyeballs, which are retracted by muscles into the oral cavity when swallowing. The digestive tract is short, ending in a cloaca.

The respiratory organs in the larvae of amphibians and in some caudate amphibians that permanently live in water are represented by external gills; in most adult forms of other amphibians, they are lungs. Ventilation of the lungs is carried out thanks to the movements of the sublingual apparatus, which plays the role of a pressure pump. This does not ensure effective removal of CO 2 from the lungs. Therefore, in all amphibians, pulmonary respiration is supplemented by cutaneous respiration; in many it becomes even more important than the pulmonary one, and in lungless salamanders the lungs are completely lost. Skin respiration becomes possible because the skin of amphibians is constantly moistened by the secretion of numerous skin glands. The heart, as a rule, consists of a ventricle and two atria, a sinus venosus (emptying into the right atrium) and a conus arteriosus extending from the ventricle. Oxygenated blood from the lungs enters the left atrium, and from the skin (through the vena cava system) not only venous but also arterial blood enters the right atrium. These blood flows are greater or to a lesser extent mix in the ventricle. Thus, in the heart of amphibians there is no complete separation of venous and arterial blood.

Trunk kidneys (mesonephric); the excretory ducts of the gonads and kidneys open into the cloaca. The main end product of protein metabolism is urea. The need to keep the skin moist limits the distribution of amphibians on land to wet habitats. At the same time, the high permeability of the skin to water prevents the life of amphibians in the sea, since in salt water there is a danger of dehydration as a result of osmotic processes. But certain species of amphibians (for example, the crab-eating frog, Capa cancrivora) have adapted to life in the brackish water of the estuaries.

Fertilization is external (in tailless amphibians and the most primitive tailed amphibians) or internal. Most amphibians are oviparous; few species are viviparous. The eggs develop in water; Some species of amphibians have developed adaptations for the development of eggs outside water bodies (in burrows, special “nests” formed from the mucous secretions of the skin glands of the parents, on the mother’s body, etc.). The life cycle includes the stage of an aquatic larva, which is characterized by a fish-like body with a caudal fin, one circle of blood circulation, head (pronephric) kidneys, etc. Like fish, they have lateral line organs (they are preserved in adult individuals of species that live permanently in water). The larvae transform into the adult stage through metamorphosis. In the few amphibians that lay eggs on land (for example, leaf frogs, Eleutherodactylus), development is direct, without metamorphosis. Some tailed amphibians, for example, Mexican Ambystoma (Ambystoma texicanum), Alpine newt (Triturus alrestris), are capable of reproducing at the larval stage (neoteny).

Adult amphibians are predators, feeding on a variety of invertebrates and, to a lesser extent, vertebrates. Amphibians are an important component natural ecosystems(they regulate the number of many species of invertebrates and serve as food for other vertebrates). In a number of countries, some species of amphibians are consumed by humans. Certain species of amphibians are classic laboratory animals.

Lit.: Noble G. K. The biology of the Amphibia. 3rd ed. Gloucester, 1962; Physiology of the Amphibia. N. Y.; L., 1974-1976. Vol. 1-3; Key to amphibians and reptiles of the fauna of the USSR. M., 1977; Life of animals. 2nd ed. M., 1985. T. 5: Amphibians. Reptiles; Duellman W. E., Trueb L. Biology of Amphibians. N.Y., 1986; Carroll R. Paleontology and evolution of vertebrates. M., 1992. T. 1; Zug G. R., Vitt L. J., Caldwell J. R. Herpetology. 2nd ed. San Diego, 2001; Herpetology. Upper Saddle River, 2004.

Which consists of three modern orders: tailless (frogs and toads), legless (caecilians) and tailed (newts and salamanders). The ancestors of modern amphibians were the first animals to leave the water and adapt to life on land.

Amphibian larvae begin their life path in water, usually fresh, and undergo a complex process of metamorphosis before transforming into an adult. Their skin is moist without scales, feathers or fur.

The life cycle of amphibians reflects their evolutionary history of transition from life in water to life on land. Most amphibians lay eggs in fresh water, but there are species that prefer salt water or dry land. Surprisingly, some species carry eggs on their bodies. Although the life cycle of amphibians varies from species to species, they all have the following three main stages of development: egg → larva → adult.

Eggs (eggs) of amphibians without a waterproof shell. Instead, they consist of a gelatinous shell that must remain moist for the larva to survive. There are small holes in the eggs through which the tiny larvae emerge to undergo metamorphosis into adults.

Many amphibians are able to absorb oxygen directly into the bloodstream, and also release carbon dioxide into the atmosphere through the skin. The skin of amphibians does not have scales or hair. It is smooth and often moist, making it quite permeable to gases and water.

The permeability of their skin makes amphibians especially vulnerable to toxins in the air and water, such as herbicides, pesticides and other pollutants. For this reason, we are seeing dramatic declines or extinctions of amphibian species in many areas around the world.

The first amphibians evolved from lobe-finned fishes approximately 370 million years ago, during the Devonian period. Early amphibians included the following creatures: diplocaulus, ophiderpeton, adelospondylus and pelodosotis. The world of the first amphibians was completely different from what we see today. A world without birds, mammals and reptiles. Invertebrates and many prehistoric plants that colonized the Earth. It was quiet place devoid of birdsong and the growls of predators. The land was open to amphibians, who began a new and important stage in the history of life on our planet. Some fish species have developed lungs.

Scientists believe that the ancestors of amphibians were crossopterygians, a group of primitive lobe-finned fish. They evolved several key features: a musculoskeletal framework to support their body weight on land, as well as nostrils and leg bones.

Most amphibians never completely lose contact with their aquatic habitat. Some amphibians return to the water to reproduce, and some species remain in the water throughout life cycle. Many amphibians undergo a complex process of metamorphosis before becoming adults.

In this article, we will talk about a large group of the oldest animals living on our planet - amphibians, or as they are also called amphibians, or rather, we will briefly introduce you to the types of amphibians inhabiting planet Earth.

Types of amphibians and their diversity

So, amphibians (lat. Amphibia) are a fairly large class of four-legged vertebrates, considered primitive and occupying an intermediate place between aquatic vertebrates and terrestrial vertebrates. In total there are currently more than 6,500 modern species amphibians that spread throughout the globe. In Russia, for example, only 28 representatives of the class in question are registered, but, for example, in Madagascar there are about 250 species of amphibians, as they say, of all sizes and colors.

The word “amphibian” itself comes from the ancient Greek “amphibios” and literally means “two types of life” or “both types”. Previously, this term was applied to animals that are capable of leading a normal life, both on land and in water, such as pinnipeds. Later, this term began to be applied to four-legged vertebrates other than amniotes (higher vertebrates). Currently, all amphibians are divided into 4 subclasses, 3 of which are completely extinct today. Let's briefly look at the classification of amphibians that exist and have ever existed on Earth:

• Labyrinthodontia (lat. Labyrinthodontia) is a completely extinct subclass that existed in the Paleozoic and early Mesozoic periods:

• Anthracosaurs;

• Colosteids;

• Temnospondylus;

• Thin-vertebrates (lat. Lepospondyli) are a completely extinct subclass that existed in the Paleozoic period:

• Microsauria;

• Acherontiscidae;

• Nectridea;

• Adelospondyli;

• Lysorophia;

• Aistopoda.

• Batrachosaurs or otherwise Reptiliomorphs (lat. Batrachosauria) is a completely extinct subclass that existed from the late Devonian to the late Permian period:

• Anthracosaurs (lat. Anthracosauria);

• Seymouriamorpha (lat. Seymouriamorpha);

• Lissamphibia (lat. Lissamphibia) is a modern subclass of amphibians, including all types of amphibians that currently exist - newts, toads, salamanders, frogs and caecilians:

• The order Tailless Amphibians (Latin Anura) are all frogs and toads belonging to more than 5,600 species of amphibians from 48 known families;

• The order Tailed amphibians (lat. Caudata or otherwise Urodela) are all living salamanders and newts, belonging to more than 570 species of amphibians from 10 families;

• The order Legless amphibians (lat. Gymnophiona or otherwise Apoda) are modern caecilians, animals similar to earthworms, of which there are about 190 species, and they belong to 10 families.

Crocodile newt

As you understand, there are still a great many species of amphibians that inhabit our entire planet, despite the fact that many have long since become extinct - hundreds and even thousands. They all look completely different. Some are medium in size, while others are very miniature. Some are brightly and elegantly colored, while others, on the contrary, have a dull camouflage color. Some are not poisonous, while others are very dangerous not only for small or large animals, but also for humans.

For example, a tiny, only 2-3 centimeter bright yellow frog that lives in tropical forests Colombia, with the loud name The terrible leaf climber (lat. Phyllobates terribilis) is capable of killing more than one person. The fact is that her skin is covered with poisonous mucus containing the toxic substance batrachotoxin. Local Indians use this mucus to make poisoned arrows. They call this frog "cocoi". The poison of one such frog is enough for 50 poisoned arrows, and only 2 mg is enough to kill one person. purified venom of this amphibian.

Some species of amphibians prefer wet places, others alternate being in water with being on land, others spend most of their lives in trees, and still others live exclusively in water. Moreover, some amphibians live in fresh water, while others live only in sea salt water, such as, for example, sea ​​toad(lat. Bufo marinus). Later we will look at individual species of amphibians, their habitat and way of life.

Some species of amphibians hibernate for a long time when extreme conditions for them occur, while others stay awake the entire season and feel great. Some are active at night, while others are active during the day.

Axolotl

Despite the fact that the vast majority of these animals prefer warm, or even hot, conditions, some species of amphibians are able to withstand quite long periods of freezing or drying out. There are amphibians that are able to restore or “grow” (regenerate) lost parts of their body.

In fact, as you understand, it is impossible to devote one article to all types of amphibians, since there are a huge number of them, and each of them has its own individual characteristics.

Next, we will continue this large topic, and we will definitely tell you, if possible, about individual types of amphibians, i.e. we will dedicate many new ones to each of them interesting articles. We hope you found it interesting. And see you on the pages of “Underwater World”.

In conclusion, I would like to recommend watching videos that will introduce you to some interesting species of amphibians. And after the video, you will find links to new articles that will tell you a lot of interesting things about the amazing representatives of the amphibian world.