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Subclass lungfish. living fossils

When, during a six-month drought, Lake Chad in Africa reduces its area by almost one third and the muddy bottom is exposed, the locals go fishing, taking with them ... hoes. They look for molehill-like mounds on the dried bottom, and dig out of each clay capsule with fish folded in half, like a hair clip.

This fish is called protopterus ( Protopterus) and belongs to subclass 1 lungfish ( Dipnoi). In addition to the gills common to fish, representatives of this group also have one or two lungs - a modified swim bladder, through the walls of which are braided with capillaries, gas exchange occurs. Atmospheric air for breathing fish capture by mouth, rising to the surface. And in their atrium there is an incomplete septum, which continues in the ventricle. Venous blood from the organs of the body enters the right half of the atrium and the right half of the ventricle, and blood from the lung goes to the left side of the heart. Then oxygenated "pulmonary" blood enters mainly into those vessels that lead through the gills to the head and organs of the body, and blood from the right side of the heart, also passing through the gills, largely enters the vessel leading to the lung. And although poor and oxygen-rich blood is partially mixed both in the heart and in the vessels, one can still talk about the beginnings of two circles of blood circulation in lungfish.

Lungfish is a very old group. Their remains are found in deposits of the Devonian period. Paleozoic era. For a long time, lungfish were known only from such fossils, and it was not until 1835 that a protopter living in Africa was found to be a lungfish. In total, as it turned out, representatives of six species of this group have survived to this day: the Australian horntooth from the order of one-lungs, the American flake - a representative of the order of two-lungs and four species of the African genus Protopterus, also from the order of the two-lungs. All of them, as, apparently, and their ancestors, freshwater fish.

Australian horntooth(Neoceratodus forsteri) is found in a very small area - in the basins of the Burnett and Mary rivers in the northeast of Australia. it big fish with body length up to 175 cm and weight over 10 kg. The massive body of the horntooth is laterally compressed and covered with very large scales, and the fleshy paired fins resemble flippers. The horntooth is colored in uniform colors - from reddish-brown to bluish-gray, the belly is light.

This fish lives in rivers slow flow heavily overgrown with aquatic and emersed vegetation. Every 40 - 50 minutes, the horntooth emerges and exhales air from the lung with noise, making a characteristic moaning-grunting sound that spreads far over the surroundings. Taking a breath, the fish sinks to the bottom again.

Most of the time the horntooth spends at the bottom of deep pools, where it lies on its belly or stands, leaning on its flipper-like fins and tail. In search of food - various invertebrates - he slowly crawls, and sometimes "walks", leaning on the same paired fins. It swims slowly, and only when frightened does it use its powerful tail and show the ability to move quickly.

The dry season when the rivers are getting shallow, the horntooth survives in preserved water pits. When a fish dies in superheated, stagnant and practically devoid of oxygen water, and the water itself turns into a fetid slurry as a result of putrefactive processes, the horntooth remains alive due to its pulmonary respiration. But if the water dries up completely, these fish still die, because, unlike their African and South American relatives, they cannot hibernate.

Spawning of the horntooth occurs during the rainy season, when the rivers swell and the water in them is well aerated. Large, up to 6–7 mm in diameter, the fish lays eggs on aquatic plants. After 10–12 days, larvae hatch, which, until the yolk sac is resorbed, lie on the bottom, only occasionally moving a short distance. On the 14th day after hatching, the pectoral fins appear in the fry, and from the same time, the lung probably begins to function.

Horntooth has tasty meat, and it is very easy to catch it. As a result, the number of these fish has been greatly reduced. Horntooths are now under protection and attempts are being made to acclimatize them in other water bodies of Australia.

The history of one of the most famous zoological hoaxes is connected with the horntooth. In August 1872, the director of the Brisbane Museum was touring north-eastern Australia, and one day he was informed that a breakfast had been prepared in his honor, for which the natives brought very rare fish, caught by them 8-10 miles from the place of the feast. And indeed, the director saw a fish of a very strange appearance: a long massive body was covered with scales, the fins looked like flippers, and the snout looked like a duck's beak. The scientist made drawings of this unusual creature, and after returning he handed them over to F. De Castelnau, a leading Australian ichthyologist. Castelnau was not slow to describe a new genus and species of fish from these drawings - Ompax spatuloides. There was a rather lively discussion about family ties new species and its place in the classification system. There were many reasons for disputes, since in the description Ompax much remained unclear and there was no information on anatomy at all. Attempts to obtain a new specimen were unsuccessful. There were skeptics who expressed doubts about the existence of this animal. Still mysterious Ompax spatuloides for almost 60 years it continued to be mentioned in all reference books and summaries of the Australian fauna. The mystery was solved unexpectedly. In 1930, an article appeared in the Sydney Bulletin, the author of which wished to remain anonymous. This article reported that an innocent joke was played on the ingenuous director of the Brisbane Museum, since the Ompax served to him was prepared from the tail of an eel, the body of a mullet, the head and pectoral fins of a horntooth, and the snout of a platypus. From above, all this ingenious gastronomic structure was skillfully covered with scales of the same horntooth ...

African lungfish - protopters - have filiform paired fins. The largest of the four species big protopter(Protopterus aethiopicus) can reach a length of more than 1.5 m, and the usual length small protopter(P.amphibius) - about 30 cm.

These fish swim, serpentine bending the body like eels. And along the bottom, with the help of their thread-like fins, they move like newts. In the skin of these fins there are numerous taste buds - as soon as the fin touches an edible object, the fish turns around and grabs the prey. From time to time, protopters rise to the surface, swallowing through the nostrils 2 atmospheric air.

Protopters live in Central Africa, in lakes and rivers flowing through swampy areas subject to annual flooding and drying up during the dry season. When the reservoir dries up, when the water level drops to 5–10 cm, protopters begin to dig holes. The fish grabs the soil with its mouth, crushes it and throws it out through the gill slits. Having dug a vertical entrance, the protopter makes a chamber at its end, in which it is placed, bending the body and putting its head up. While the water is still wet, the fish rises from time to time to take a breath of air. When the film of drying water reaches the upper edge of the liquid silt lining the bottom of the reservoir, part of this silt is sucked into the hole and clogs the exit. After that, the protopter is no longer shown on the surface. Before the cork is completely dry, the fish, poking into it with its snout, compacts it from below and lifts it somewhat in the form of a cap. When dry, the cap becomes porous and allows enough air to pass through to keep sleeping fish alive. As soon as the cap hardens, the water in the burrow becomes viscous from the abundance of mucus secreted by the protopter. As the soil dries up, the water level in the hole drops, and eventually the vertical passage turns into an air chamber, and the fish, bending over in half, freezes in the lower, expanded part of the hole. A slimy cocoon is formed around it, tightly adhering to the skin, in the upper part of which there is a thin passage through which air penetrates to the head. In this state, the protopter waits next period rains, which occurs after 6-9 months. Under laboratory conditions, the protopters were kept in hibernation for more than four years, and at the end of the experiment they woke up safely.

Protopter buried in mud during a drought

During hibernation, the metabolic rate of protopters sharply decreases, but nevertheless, in 6 months, the fish loses up to 20% of the initial mass. Since energy is supplied to the body through the breakdown of not fat reserves, but mainly muscle tissue, the products of nitrogen metabolism accumulate in the body of the fish. During the active period, they are excreted mainly in the form of ammonia, but during hibernation, ammonia is converted into less toxic urea, the amount of which in the tissues by the end of hibernation can be 1–2% of the mass of the fish. The mechanisms that provide resistance to such high concentrations of urea have not yet been elucidated.

When reservoirs fill with the onset of the rainy season, the soil gradually soaks, water fills the air chamber, and the protopter, breaking through the cocoon, periodically begins to stick out its head and inhale atmospheric air. When water covers the bottom of the reservoir, the protopter leaves the hole. Soon, urea is excreted from his body through the gills and kidneys.

A month and a half after leaving hibernation, reproduction begins in protopters. At the same time, the male digs a special spawning hole at the bottom of the reservoir, among the thickets of vegetation, and lures one or several females there, each of which lays up to 5 thousand eggs 3–4 mm in diameter. After 7–9 days, larvae appear with a large yolk sac and 4 pairs of pinnate external gills. With the help of a special cement gland, the larvae are attached to the walls of the nesting hole.

After 3–4 weeks, the yolk sac completely resolves, the fry begin to actively feed and leave the hole. At the same time, they lose one pair of external gills, and the remaining two or three pairs can persist for many more months. In a small protopter, three pairs of external gills are retained until the fish reaches the size of an adult.

After leaving the spawning hole, protopter fry swim for some time only next to it, hiding there at the slightest danger. All this time, the male is near the nest and actively defends it, rushing even at an approaching person.

Protopter dark(P. dolloi), found in the Congo and Ogowe river basins, lives in swampy areas where the layer underground water persists during the dry season. When surface water in the summer they begin to decrease, this fish, like its relatives, burrows into the bottom mud, but digs up to a layer of liquid silt and underground water. Having settled there, the dark protopter spends the dry season without creating a cocoon and rising up from time to time to breathe fresh air.

The burrow of the dark protopter begins with an inclined course, the expanded part of which serves as a fish and a spawning chamber. According to the stories of local fishermen, such holes, if they are not destroyed by floods, serve the fish from five to ten years. Preparing the burrow for spawning, the male from year to year builds up a mound of mud around it, which eventually reaches 0.5–1 m in height.

Protopters have attracted the attention of scientists involved in the creation of sleeping pills. English and Swedish biochemists tried to isolate "hypnotic" substances from the body of hibernating animals, including the protopter. When an extract from the brains of sleeping fish was injected into the circulatory system of laboratory rats, their body temperature began to drop rapidly, and they fell asleep as quickly as if they were fainting. The sleep lasted 18 hours. When the rats woke up, no signs that they were in artificial sleep could be found in them. The extract obtained from the brains of awake protopters did not cause any effects in rats.

American flake(Lepidosiren paradoxa), or lepidosiren,- a representative of the lungfish that lives in the Amazon basin. The body length of this fish reaches 1.2 m. Paired fins are short. Lepidosiren live mainly in temporary reservoirs flooded with water during rains and floods, and feed on a variety of animal food, mainly mollusks. They may also eat plants.

When the reservoir begins to dry up, lepidosiren digs a hole at the bottom, in which it settles in the same way as the protopters, and clogs the entrance with a cork from the ground. This fish does not form a cocoon - the body of a sleeping lepidosiren is surrounded by mucus moistened groundwater. In contrast to protopters, the basis of energy metabolism during hibernation in flake is stored fat.

In 2-3 weeks after the new flooding of the reservoir, lepidosiren start breeding. The male digs a vertical burrow, sometimes bending horizontally towards the end. Some burrows reach 1.5 m in length and 15–20 cm in width. The fish drags leaves and grass to the end of the hole, on which the female spawns eggs 6–7 mm in diameter. The male remains in the burrow guarding the eggs and hatched fry. The mucus secreted by its skin has a coagulating effect and cleans the water in the hole from turbidity. In addition, at this time, branching skin outgrowths 5–8 cm long, abundantly supplied with capillaries, develop on its ventral fins. Some ichthyologists believe that during the period of caring for offspring, lepidosiren does not use pulmonary respiration and these outgrowths serve as additional external gills. There is also an opposite point of view - rising to the surface and taking a sip fresh air, the male lepidosiren returns to the burrow and, through the capillaries on the outgrowths, gives off part of the oxygen to the water, in which eggs and larvae develop. Be that as it may, after a period of reproduction, these outgrowths resolve.

The larvae hatched from the eggs have 4 pairs of strongly branching external gills and a cement gland, with which they attach themselves to the walls of the nest. Approximately one and a half months after hatching, when the fry reach a length of 4–5 cm, they begin to breathe with the help of lungs, and the external gills dissolve. At this time fry of lepidosiren leave the hole.

The local population appreciates the tasty meat of the lepidoserene and intensively exterminates these fish.

Scheme of the arterial circulation of lungfish:
1-4 - the first-fourth pairs of gill arterial arches; 5 - dorsal aorta;
6 - abdominal aorta; 7 - pulmonary artery; 8 - pulmonary vein.

Literature

Life of animals. Volume 4, part 1. Fish. – M.: Enlightenment, 1971.

Science and life; 1973, No. 1; 1977, No. 8.

Naumov N.P., Kartashev N.N. Zoology of vertebrates. Part 1. Lower chordates, jawless, fish, amphibians: Textbook for biologist. specialist. Univ. – M.: graduate School, 1979.

1 According to other ideas, lungfish ( Dipneustomorpha) – superorder in the subclass lobe-finned ( Sarcopterygii).

2 In most fish, the nostrils are blindly closed, but in lungfish they are connected to the oral cavity.

This subclass includes only 3 modern representative who lead a sedentary lifestyle fresh waters and have the ability to breathe not only oxygen dissolved in water, but also atmospheric air with the help of lungs.

Lungfish reach 1-2 m in length, have an elongated body covered with a tiled cycloid bone scales. They do not have separate dorsal and anal fins: they merge with a large diphycercal caudal fin. The paired fins are shaped either as wide lobes or as long cords.

The notochord persists throughout life, and the vertebral bodies do not develop, but there are cartilaginous upper and lower arches and ribs. Skull, unlike all the others bony fish, autostylic, cartilaginous, but complicated by chondral and integumentary bones. Secondary jaws (intermaxillary, maxillary and dentary bones) are absent. Gill arches, including four or five pairs, cartilaginous. The shoulder girdle is well developed, cartilaginous, but covered with false bones. Pelvic girdle in the form of an unpaired cartilaginous plate. The paired fins are cartilaginous, like a biserial archipterygium. In a typical form, bi-serial fins are found in ceratodes, and in two other modern lungfish, fins are in the form of thread-like appendages. The external skeleton of both paired and unpaired fins consists of dissected horny rays.

The brain is characterized by a significant size of the forebrain, which is divided into twohemispheres not only outside, but also inside, so that there are two independent lateral ventricles. The midbrain is relatively small. The cerebellum is extremely poorly developed, which is associated with the low mobility of the lungfish.

(according to Goodrich):

1 - pelvis, 2 - basals, 3 - radials

(according to Parker):

1-4 - afferent branchial arteries, 5 - 8 - efferent branchial arteries, 9 - pulmonary arteries, 10 - arterial cone, 11 - left atrium, 12 - right atrium, 13 - ventricle of the heart, 14 - jugular veins, 15 - brachial veins , 16 - subscapular veins, 17 - left posterior cardinal vein, 18 - pulmonary vein, 19 - posterior pudendal vein, 20 - dorsal aorta, 21 - Cuvier ducts

The teeth are very peculiar; they are fused into plates, the sharp tops of which are directed forward. A pair of such teeth is placed on the lid oral cavity, and the ceratoda, in addition, has a pair of flat teeth on the lower jaw. The intestine is equipped with a well-developed spiral valve and opens into the cloaca.

Along with the gills, there are lungs that communicate with the ventral side of the esophagus and have a cellular structure of the inner wall. There is no swim bladder. In connection with the development of pulmonary respiration, in addition to the external nostrils, there are also internal nostrils.

The circulatory system is distinguished by the following features: 1) it departs from the pair of gill arteries closest to the heart along the pulmonary artery, while the pulmonary veins flowing into the left half of the atrium depart from the lung; when the gills function, already oxidized blood enters the pulmonary arteries, so that the lung is inactive, but when the gills do not function due to a lack of oxygen in the water, then venous blood enters the lung; 2) the atrium is subdivided by an incomplete septum into two halves (right and left), and the arterial cone is equipped with a longitudinal valve dividing it into two parts; 3) along with the posterior cardinal veins, there is a posterior vena cava, into which the renal veins flow. Thus, the venous system of lungfish occupies an intermediate position between the circulatory system of aquatic and terrestrial vertebrates.

The genitourinary system is arranged in general according to the type of genitourinary systems cartilaginous fish, and the oviducts (Müllerian canals) open into the body cavity, but the efferent ducts of the testes may be absent. Then the seed comes out, apparently through the abdominal pores. In addition, lungfish males lack copulatory organs; insemination is external. The caviar is quite large, about 7 mm in diameter, surrounded by a gelatinous shell and resembles amphibian caviar; deposited among vegetation and often sinks to the bottom.

Thus, lungfish combine in their organization, on the one hand, a number of very primitive features such as the absence of vertebral bodies, mainly a cartilaginous skeleton, on the other hand, they have a real lung, the development of which is associated with the development of internal nostrils and a double circle of blood circulation. The biserial type of paired fins is a completely peculiar feature.

More interesting articles

Early lungfish (Dipnoi) show great resemblance to ancient lobe-finned fish; they also had two dorsal, one anal and heterocercal caudal fins, cosmoid scales, a generally similar arrangement of the integumentary bones of the cranium, and internal nostrils. But, on the other hand, the upper jaw fused with the cranium (autostyly), the intermaxillary, maxillary and dentary bones were already lost and there were palatine dental plates characteristic of all lungfish. Finally, the paired fins were of the biserial type. It should be noted, however, that some of the later Loopfins had fins transitional to biserial.

The evolutionary series of lungfish from Dipterus to ceratoda (according to Abel), sequentially from bottom to top: Dipterus valensiensis (Lower Devonian), Dipterus macropterus (Middle Devonian), Scaumenacia curta (Upper Devonian), Phaneropleuron andersoni (Upper Devonian), Uronema lobatus (Lower Stony coal), Neoceratodus forsteri (modern)

The evolution of lungfish has now been traced very fully, and we have full row linking the Lower Devonian Dipterus with the modern ceratod. Apparently, the division of the lobe-finned and lungfish proceeded depending on various ways diet: the lobe-finned fish-eating predators, while the lungfish switched to feeding mainly on crustaceans and mollusks, in connection with which their teeth merged into plates, and they turned into modern slow creatures. fish arterial circulation

This fish is called protopterus (Protopterus) and belongs to the subclass 1 lungfish (Dipnoi). In addition to the gills common to fish, representatives of this group also have one or two lungs - a modified swim bladder, through the walls of which are braided with capillaries, gas exchange occurs. Atmospheric air for breathing fish capture by mouth, rising to the surface. And in their atrium there is incomplete septum continuing in the stomach. The venous blood coming from the organs of the body enters the right half of the atrium and the right half of the ventricle, and the blood coming from the lung goes to the left side of the heart. Then oxygenated "pulmonary" blood enters mainly into those vessels that lead through the gills to the head and organs of the body, and blood from the right side of the heart, also passing through the gills, largely enters the vessel leading to the lung. And although poor and oxygen-rich blood is partially mixed both in the heart and in the vessels, one can still talk about the beginnings of two circles of blood circulation in lungfish.

The lungfish are a very ancient group. Their remains are found in deposits of the Devonian period of the Paleozoic era. For a long time, lungfish were known only from such fossilized remains, and it was not until 1835 that the protopter living in Africa was found to be a lungfish. In total, as it turned out, representatives of six species of this group have survived to this day: the Australian horntooth from the order of one-lungs, the American flake - a representative of the order of two-lungs and four species of the African genus Protopterus, also from the order of two-lungs. All of them, as, apparently, and their ancestors, freshwater fish.

The Australian horntooth (Neoceratodus forsteri) is found in a very small area - in the basins of the Burnett and Mary rivers in the northeast of Australia. This is a large fish with a body length of up to 175 cm and a weight of over 10 kg. The massive body of the horntooth is laterally compressed and covered with very large scales, and the fleshy paired fins resemble flippers. The horntooth is colored in uniform colors - from reddish-brown to bluish-gray, the belly is light.

This fish lives in slow-flowing rivers, heavily overgrown with aquatic and surface vegetation. Every 40 - 50 minutes, the horntooth emerges and exhales air from the lung with noise, making a characteristic moaning-grunting sound, which spreads far over the surroundings. Taking a breath, the fish sinks to the bottom again.

The period of drought, when the rivers become shallow, the horntooth survives in the preserved pits with water. When a fish dies in superheated, stagnant and practically devoid of oxygen water, and the water itself turns into a fetid slurry as a result of putrefactive processes, the horntooth remains alive due to its pulmonary respiration. But if the water dries up completely, these fish still die, because, unlike their African and South American relatives, they cannot hibernate.

Spawning of the horntooth occurs during the rainy season, when the rivers swell and the water in them is well aerated. Large, up to 6-7 mm in diameter, fish lay eggs on aquatic plants. After 10-12 days, larvae hatch, which, until the yolk sac is resorbed, lie on the bottom, only occasionally moving a short distance. On the 14th day after hatching, the pectoral fins appear in the fry, and from the same time, the lung probably begins to function.

The history of one of the most famous zoological hoaxes is connected with the horntooth. In August 1872, the director of the Brisbane Museum was touring northeastern Australia, and one day he was informed that a breakfast had been prepared in his honor, for which the natives brought a very rare fish caught by them 8-10 miles from the feast. And indeed, the director saw a fish of a very strange appearance: a long massive body was covered with scales, the fins looked like flippers, and the snout looked like a duck's beak. The scientist made drawings of this unusual creature, and after returning, he handed them over to F. De Castelnau, a leading Australian ichthyologist. Castelnau was quick to describe a new genus and species of fish, Ompax spatuloides, from these drawings. A rather heated discussion followed about the relationship of the new species and its place in the classification system. There were many grounds for controversy, since in the description of Ompax much remained unclear and there was no information on anatomy at all. Attempts to obtain a new specimen were unsuccessful. There were skeptics who expressed doubts about the existence of this animal. Nevertheless, the mysterious Ompax spatuloides continued to be mentioned in all reference books and summaries of the Australian fauna for nearly 60 years. The mystery was solved unexpectedly. In 1930, an article appeared in the Sydney Bulletin, the author of which wished to remain anonymous. This article reported that an innocent joke was played on the ingenuous director of the Brisbane Museum, since the Ompax served to him was prepared from the tail of an eel, the body of a mullet, the head and pectoral fins of a horntooth, and the snout of a platypus. From above, all this ingenious gastronomic structure was skillfully covered with scales of the same horntooth ...

African lungfish - protopters - have filiform paired fins. The largest of the four species - the large protopter (Protopterus aethiopicus) can reach a length of more than 1.5 m, and the usual length of the small protopter (P.amphibius) is about 30 cm.

Protopters live in Central Africa, in lakes and rivers that flow through swampy areas that are subject to annual flooding and dry up during the dry season. When the reservoir dries up, when the water level drops to 5-10 cm, protopters begin to dig holes. The fish grabs the soil with its mouth, crushes it and throws it out through the gill slits. Having dug a vertical entrance, the protopter makes a chamber at its end, in which it is placed, bending the body and putting its head up.

While the water is still wet, the fish rises from time to time to take a breath of air. When the film of drying water reaches the upper edge of the liquid silt lining the bottom of the reservoir, part of this silt is sucked into the hole and clogs the exit. After that, the protopter is no longer shown on the surface. Before the cork is completely dry, the fish, poking into it with its snout, compacts it from below and lifts it somewhat in the form of a cap. When dry, the cap becomes porous and allows enough air to pass through to keep sleeping fish alive. As soon as the cap hardens, the water in the burrow becomes viscous from the abundance of mucus secreted by the protopter. As the soil dries up, the water level in the hole drops, and eventually the vertical passage turns into an air chamber, and the fish, bending over in half, freezes in the lower, expanded part of the hole. A slimy cocoon is formed around it, tightly adhering to the skin, in the upper part of which there is a thin passage through which air penetrates to the head. In this state, the protopter waits for the next rainy period, which occurs in 6-9 months. Under laboratory conditions, the protopters were kept in hibernation for more than four years, and at the end of the experiment they woke up safely.

During hibernation, the metabolic rate of protopters sharply decreases, but nevertheless, in 6 months, the fish loses up to 20% of the initial mass. Since energy is supplied to the body through the breakdown of not fat reserves, but mainly muscle tissue, the products of nitrogen metabolism accumulate in the body of the fish. During the active period, they are excreted mainly in the form of ammonia, but during hibernation, ammonia is converted into less toxic urea, the amount of which in the tissues by the end of hibernation can be 1-2% of the mass of the fish. The mechanisms that provide resistance to such high concentrations of urea have not yet been elucidated.

A month and a half after leaving hibernation, reproduction begins in protopters. At the same time, the male digs a special spawning hole at the bottom of the reservoir, among the thickets of vegetation, and lures one or several females there, each of which lays up to 5 thousand eggs with a diameter of 3-4 mm. After 7-9 days, larvae appear with a large yolk sac and 4 pairs of feathery external gills. With the help of a special cement gland, the larvae are attached to the walls of the nesting hole.

After 3-4 weeks, the yolk sac completely resolves, the fry begin to actively feed and leave the hole. At the same time, they lose one pair of external gills, and the remaining two or three pairs can persist for many more months. In a small protopter, three pairs of external gills are retained until the fish reaches the size of an adult.

The dark protopter (P. dolloi), found in the basins of the Congo and Ogowe rivers, lives in swampy areas where a layer of underground water is preserved during the dry season. When surface waters begin to decrease in summer, this fish, like its relatives, burrows into the bottom mud, but digs up to a layer of liquid silt and underground water. Having settled there, the dark protopter spends the dry season without creating a cocoon and rising up from time to time to breathe fresh air.

The burrow of the dark protopter begins with an inclined course, the expanded part of which serves as a fish and a spawning chamber. According to the stories of local fishermen, such holes, if they are not destroyed by floods, serve the fish from five to ten years. Preparing the hole for spawning, the male from year to year builds up a mud mound around it, which eventually reaches 0.5-1 m in height.

Protopters have attracted the attention of scientists involved in the creation of sleeping pills. English and Swedish biochemists tried to isolate "hypnotic" substances from the body of hibernating animals, including the protopter. When an extract from the brain of sleeping fish was injected into circulatory system laboratory rats, their body temperature began to drop rapidly, and they fell asleep as quickly as if they were fainting. The sleep lasted 18 hours. When the rats woke up, no signs that they were in artificial sleep could be found in them. The extract obtained from the brains of awake protopters did not cause any effects in rats.

American flake (Lepidosiren paradoxa), or lepidosiren, is a lungfish that lives in the Amazon. The body length of this fish reaches 1.2 m. Paired fins are short. Lepidosiren live mainly in temporary reservoirs flooded with water during rains and floods, and feed on a variety of animal food, mainly mollusks. They may also eat plants.

When the reservoir begins to dry up, lepidosiren digs a hole at the bottom, in which it settles in the same way as the protopters, and clogs the entrance with a cork from the ground. This fish does not form a cocoon - the body of a sleeping lepidosiren is surrounded by mucus moistened with groundwater. In contrast to protopters, the basis of energy metabolism during hibernation in flake is stored fat.

In 2-3 weeks after the new flooding of the reservoir, lepidosiren start breeding. The male digs a vertical burrow, sometimes bending horizontally towards the end. Some burrows reach 1.5 m in length and 15-20 cm in width. At the end of the hole, the fish drags leaves and grass, on which the female spawns eggs 6-7 mm in diameter. The male remains in the burrow guarding the eggs and hatched fry. The mucus secreted by its skin has a coagulating effect and cleans the water in the hole from turbidity. In addition, at this time, branching skin outgrowths 5-8 cm long, abundantly supplied with capillaries, develop on its ventral fins. Some ichthyologists believe that during the period of caring for offspring, lepidosiren does not use pulmonary respiration and these outgrowths serve as additional external gills. There is also an opposite point of view - having risen to the surface and gulped fresh air, the male lepidosiren returns to the hole and through the capillaries on the outgrowths gives part of the oxygen to the water, in which eggs and larvae develop. Be that as it may, after a period of reproduction, these outgrowths resolve.

The larvae hatched from the eggs have 4 pairs of strongly branching external gills and a cement gland, with which they attach themselves to the walls of the nest. Approximately one and a half months after hatching, when the fry reach a length of 4-5 cm, they begin to breathe with the help of the lungs, and the external gills dissolve. At this time fry of lepidosiren leave the hole.

The local population appreciates the tasty meat of the lepidoserene and intensively exterminates these fish.

Lungfish have only been found in the last century. Until that moment, no one had seen them live. Ideas about them were limited only to the found ancient remains. Their structural features determined such interesting name. Let's see what kind of fish is lungfish and what is so special about it. The fact is that representatives of this class can breathe not only with gills, but also with lungs.

Who are lungfish?

Representatives of this superorder of lobe-finned fish have both gill and pulmonary respiration. This is the nature of their structure. AT modern world the subclass lungfish, whose representatives are divided into two orders - horn-toothed and dilung-shaped, is quite rare. Individuals related to it live only in Africa, Australia and South America.

In addition to the usual gills, they also have lungs (one or two), which are a modified swim bladder. Through its walls, penetrated by capillaries, in fact, gas exchange occurs. Fish take in air to breathe through their mouths as they rise to the surface. In the atrium they have a septum, which continues in the ventricle. Blood through the veins comes from the organs and enters the right side of the atrium, as well as the right half of the ventricle. The blood coming from the lung goes to the left side of the heart. Interestingly, further oxygenated lung blood is coming mainly in those vessels that pass through the gills to the head and various organs. And its second part from the right side of the heart, also passing through the gills, ends up in a vessel leading to the lung. It turns out that oxygen-rich and poor blood is still partially mixed in the vessels and the heart. So, we can talk about the primitive rudiments of two circles of blood circulation in lungfish.

ancient lungfish

Lungfish are representatives of a very ancient group. Their remains are found among the sediments (Paleozoic era). Enough long time such fish were known only from fossilized remains. And in 1835, it was discovered that the protopter, which lives in Africa, is a lungfish.

The lungfish subclass, whose representatives have survived to this day, consists of only six species:

The Australian horntooth is a detachment of one-lungs.
American flake from the order of two-lungs.
Four varieties of Protopterus from Africa (two-lungs).

Apparently, they all, together with their ancestors, belong to

Australian horntooth

Australian lungfish are lungfish. They are found in a very small area of the Mary and Burnett river basins in northeastern Australia. It is up to 175 centimeters long and weighs more than ten kilograms.

The large body of the horned tooth is flattened on the sides and covered with large scales. Large paired fins look like flippers. The color of the body of the horned tooth varies from red-brown to bluish-gray, and the belly is certainly a light shade.

The fish lives in slow-flowing rivers, where surface and underwater thickets are present. Every fifty minutes, the horntooth rises to the surface and noisily expels air from the lung. At the same time, he emits not the groan, not the grunt, which is heard far enough away. Inhaling fresh air, the fish again sinks to the bottom.

Habitat of the rosogub

The horntooth spends most of its time at the bottom, lying on its belly or standing on flipper-like fins. To search for food, he begins to crawl slowly. The fish also swim very slowly. However, if you scare her, then she begins to quickly work with her tail, thereby accelerating her movement.

During periods of drought, when the rivers become completely shallow, horntooths lie in preserved pits with water. AT hot water deprived of oxygen, the whole fish dies, and it itself turns into a smelly, dirty slurry. In such conditions, only lung-breathing fish survive, whose representatives are able to breathe with their lungs. However, if the water evaporates completely, then the horntooths still die, because, unlike their South American and African relatives, they do not know how to hibernate.

Fish spawning falls during the rainy season, when the rivers overflow with water. The horntooth lays large eggs on algae. After 12 days, larvae appear, which, until the moment of resorption of the yolk sac, are at the bottom, sometimes moving slightly over short distances.

It is believed that on the 14th day after the birth of the fry, their lung begins to function. Horntooths are very tasty, and it is very easy to catch them. This is what led to a sharp reduction in their numbers. Currently, they are under protection, in addition, attempts are being made to relocate them to other Australian reservoirs.

Protoptera - African lungfish

Protopters are also lungfish. They live in Africa and have filiform fins. Of the four species living on the continent, the largest - a large protopter - reaches a length of more than one and a half meters. The average length of the fish is about thirty centimeters. Fish swim like eels, wriggling their bodies. But the filamentous fins help them move along the bottom. An interesting fact is that the skin of the fins is rich in receptors. As soon as the fin touches something edible, the fish immediately grabs its prey. Periodically, the protopter floats up and inhales fresh air. Protopters live in central regions Africa. What places do lungfish choose to live? Representatives of this species prefer rivers and lakes in swampy areas, which are annually flooded during rains and dry up during droughts. During the dry season, the water level drops from five to ten centimeters. At this time, the protopters begin to dig holes for themselves.

The fish absorbs the soil with its mouth, and then crushes it and throws it out through the gills. The hole is a vertical passage, at the end of which there is a chamber, where, in fact, the protopter is located, bent in half and exposing its head.

Until the water is completely dry, the fish rises to breathe. And then liquid sludge is sucked into the hole, blocking the exit. Then the protopter can't get out. He just pokes his muzzle into the plug of silt, lifting it up. After drying, it becomes porous and allows oxygen to pass through, which makes it possible for fish to survive while hibernating.

The water in the burrow gradually becomes very viscous due to the mucus secreted by the protopter. The soil gradually dries out more and more, and the water level in the hole drops. As a result, the vertical stroke is filled with air. Bending over, the fish freezes in the lower chamber. A cocoon of mucus forms around her body. It is in this state that the protopter is waiting for the rainy period, which comes only after 6 - 9 months.

Behavior of fish during the dry season

Lungfish are quite interesting in their behavior and living conditions. Representatives (photos are given in the article) of this group participated in laboratory studies. So, the protopters were kept in hibernation for more than four years, and at the end of the research they woke up safely.

During hibernation in fish, metabolic processes are greatly reduced. Nevertheless, in six months, protopters lose up to 20 percent of their mass. Energy in the body comes from the breakdown of muscle tissue, therefore ammonia accumulates in the body. During the active period of the existence of fish, it calmly goes outside, but during hibernation it turns into a very toxic urea, the concentration of which is quite high. But the poisoning of the body does not occur. How such stability arises has not yet been clarified.

With the beginning of the rainy season, a gradual soaking of the soil begins, water fills the hole, the protopter, breaking the cocoon, periodically sticks out its head and inhales the air. As soon as the water completely covers the bottom of the reservoir, the fish will leave the hole. After a month and a half, the protopters will begin the breeding season. At this time, the male digs a new norm in the thickets and lures the female there, who will lay up to 5 thousand eggs. And after 7 days the larvae will appear. And after another 4 weeks, the fry begin to feed on their own and leave the mink. For some time they swim next to her, hiding at the slightest danger. Throughout this period, the male is always near the hole and protects it from enemies.

Protopter dark

Considering the topic "Lung-breathing fish: representatives, names", it is necessary to recall one more representative of this class - the dark protopter. It lives in the Congo and Ogowe basins, preferring wetlands where underground level water is conserved even during drought. When the water begins to decrease in the river, the fish burrow into the bottom silt, reaching the underground water. There, the protopter spends the entire dry period, while not creating a cocoon, periodically it rises to the surface to inhale air.

The hole of the fish is an inclined course and a chamber at the end. Fishermen say that such a shelter serves the protopter for five to ten years. Spawning also takes place in the same burrow. Males prepare for this event in advance by building up a mound of mud around it, which can reach one meter in height.

Lungfish, briefly described by us in the article, have always attracted the attention of scientists, they are so unusual and interesting. Protopters have interested researchers in sleeping pills. Biochemists in Sweden and England tried to isolate substances from fish organisms that enable them to hibernate. And here's what's interesting: when the extract from the brain of sleeping fish was injected into the blood of laboratory rats, the body temperature of the subjects began to drop sharply, they fell asleep very quickly, almost instantly. Sleep lasted up to 18 hours. After awakening, the rats failed to detect any sign of artificial sleep. The substance did not give any adverse reactions.

American flake, or lepidosiren

The considered examples of lungfish clearly demonstrate their adaptability to living conditions that are completely unsuitable for habitation. And yet, even under such circumstances, thanks to the ability to breathe in two ways, the fish feel great.

The class lungfish, whose representatives we have discussed above, also includes the American flake, which lives in the Amazon basin. The length of the fish reaches 1.2 meters. It lives, as a rule, in temporary reservoirs, which are flooded during the rainy season or floods. The flake feeders feed on various animal foods, mainly mollusks. Perhaps they eat vegetable food. When the reservoir dries up, the fish lie on the bottom of the hole and clog it with a cork. However, they do not form cocoons. Sleeping fish are surrounded by mucus and moistened by groundwater. The basis, unlike the protopter, is stored fat.

A couple of weeks after the flooding of the reservoir, the American flake begins to multiply. The male digs a hole, which can reach one and a half meters in length. In its very depths, he drags grass and leaves, on which the females throw eggs. The male stays in the burrow and guards the young. During this period, outgrowths appear on his ventral fins. Some ichthyologists say that these are temporary external gills for additional respiration. Others believe that with the help of these growths, the fish partially gives up the oxygen taken when it rises to the surface of the reservoir. Whether this is true or not is not known for sure. However, after the breeding season, the outgrowths disappear.

Lungfish. Representatives: coelacanth

Another representative of lungfish is coelacanths (coelacanths). They are very few in number and covered with a mysterious veil. They live near However, local fishermen have mined them in the entire history of no more than two hundred pieces. The length of the fish is from 43 to 180 centimeters, and the mass reaches 95 kg. An interesting fact is that all coelacanths were caught from September to April, and in the dark. Fishermen caught them with bait from squid or pieces of fish. Fishing rods were cast to decent depths (from 150 to 400 meters). Attempts were made to catch the coelacanth with traps or trawls, but nothing came of it. Perhaps this is due to the difficult topography of fish habitats.

Latimeria is a lungfish. She has enough interesting structure. For example, she has no vertebrae. The spine is formed by an elastic thick rod. serving as lung for lungfish, reduced to a small tube. The eyes of the coelacanth are adapted to living in the dark. The biology of coelacanth has been studied very little. In general, lungfish are very interesting in terms of their habitat. Representatives (a list of them was given by us in the article) of this class are quite unique. There are not many of them left on earth. Moreover, due to good palatability they are still being exterminated.

But as for the coelacanth, it is not so easy to catch it. Scientists suggest that she lives among the basalt rocks of the Comorian Rocks on great depth. Those rare specimens that caught the bait of fishermen, of course, were subjected to close inspection. So, in their stomachs were found the remains of deep-sea fish living at a depth of 500 to a thousand meters. Most likely, the coelacanth leads a sedentary life, although, as we have already said about the lungfish, they can make sharp throws, thanks to their strong tail. Movable paired fins help them squeeze through the crevices of the rocks. Latimeria does not tolerate bright sunlight and high temperature surface layers of water.

The last representative on earth

In fact, coelacanth is the only type of coelacanth fish that has survived to this day. Their discovery is comparable only to the discovery of a living dinosaur.

Of course, the coelacanth is very different from its ancient predecessors, which once inhabited shallow waters. coastal zone and fresh waters. Such conclusions were made by scientists on the basis of fossils found. By the way, with the help of the same fossils, experts concluded that the ancient coelacanths lived 400 million years ago, which means even before the advent of dinosaurs.

Latimeria is the only representative of the cross-finned fish on earth. Its discovery was the largest find in the zoological field in the twentieth century. It happened in 1938. Fishermen in Indian Ocean caught a very large unknown fish with quite aggressive behavior. Its study led to a stunning discovery - that this is the last representative of the lobe-finned fish on earth, which were previously considered extinct for a long time.

Coelacanth habitats have been established over the years. It gradually became clear that she lives near the three Comoros, as well as off the coast of southern Mozambique and the southwestern coast of Madagascar. And in 1998, a fish population was discovered off the Indonesian coast.

Currently, scientists are talking about two types of coelacanths - Indonesian and Kamor. How many fish there are off the coast of Indonesia is unknown, but about two hundred individuals live near the Comoros. All coelacanths are under close control. Catching this fish is strictly prohibited.

This fish is called protopterus (Protopterus) and belongs to the subclass 1 lungfish (Dipnoi). In addition to the gills common to fish, representatives of this group also have one or two lungs - a modified swim bladder, through the walls of which are braided with capillaries, gas exchange occurs. Atmospheric air for breathing fish capture by mouth, rising to the surface. And in their atrium there is an incomplete septum, which continues in the ventricle. Venous blood from the organs of the body enters the right half of the atrium and the right half of the ventricle, and blood from the lung goes to the left side of the heart. Then oxygenated "pulmonary" blood enters mainly into those vessels that lead through the gills to the head and organs of the body, and blood from the right side of the heart, also passing through the gills, largely enters the vessel leading to the lung. And although poor and oxygen-rich blood is partially mixed both in the heart and in the vessels, one can still talk about the beginnings of two circles of blood circulation in lungfish.

Lungfish are a very ancient group. Their remains are found in deposits of the Devonian period of the Paleozoic era. For a long time, lungfish were known only from such fossils, and it was not until 1835 that a protopter living in Africa was found to be a lungfish. In total, as it turned out, representatives of six species of this group have survived to this day: the Australian horntooth from the order of one-lungs, the American flake - a representative of the order of two-lungs, and four species of the African genus Protopterus, also from the order of two-lungs. All of them, as, apparently, and their ancestors, freshwater fish.

This fish lives in slow-flowing rivers, heavily overgrown with aquatic and surface vegetation. Every 40 - 50 minutes, the horntooth emerges and exhales air from the lung with noise, making a characteristic moaning-grunting sound that spreads far over the surroundings. Taking a breath, the fish sinks to the bottom again.

Spawning of the horntooth occurs during the rainy season, when the rivers swell and the water in them is well aerated. Large, up to 6–7 mm in diameter, fish lay eggs on aquatic plants. After 10–12 days, larvae hatch, which, until the yolk sac is resorbed, lie on the bottom, only occasionally moving a short distance. On the 14th day after hatching, the pectoral fins appear in the fry, and from the same time, the lung probably begins to function.

The history of one of the most famous zoological hoaxes is connected with the horntooth. In August 1872, the director of the Brisbane Museum was touring north-eastern Australia, and one day he was informed that a breakfast had been prepared in his honor, for which the natives brought a very rare fish caught by them 8-10 miles from the feast. And indeed, the director saw a fish of a very strange appearance: a long massive body was covered with scales, the fins looked like flippers, and the snout looked like a duck's beak. The scientist made drawings of this unusual creature, and after returning, he handed them over to F. De Castelnau, a leading Australian ichthyologist. Castelnau was quick to describe a new genus and species of fish, Ompax spatuloides, from these drawings. A rather heated discussion followed about the relationship of the new species and its place in the classification system. There were many grounds for controversy, since in the description of Ompax much remained unclear and there was no information on anatomy at all. Attempts to obtain a new specimen were unsuccessful. There were skeptics who expressed doubts about the existence of this animal. Nevertheless, the mysterious Ompax spatuloides continued to be mentioned for almost 60 years in all reference books and summaries of the Australian fauna. The mystery was solved unexpectedly. In 1930, an article appeared in the Sydney Bulletin, the author of which wished to remain anonymous. This article reported that an innocent joke was played on the ingenuous director of the Brisbane Museum, since the Ompax served to him was prepared from the tail of an eel, the body of a mullet, the head and pectoral fins of a horntooth, and the snout of a platypus. From above, all this ingenious gastronomic structure was skillfully covered with scales of the same horntooth ...

African lungfish - protopters - have filiform paired fins. The largest of the four species, the large protopter (Protopterus aethiopicus) can reach a length of more than 1.5 m, and the usual length of the small protopter (P.amphibius) is about 30 cm.

Protopters live in Central Africa, in lakes and rivers that flow through swampy areas that are subject to annual flooding and dry up during the dry season. When the reservoir dries up, when the water level drops to 5–10 cm, protopters begin to dig holes. The fish grabs the soil with its mouth, crushes it and throws it out through the gill slits. Having dug a vertical entrance, the protopter makes a chamber at its end, in which it is placed, bending the body and putting its head up.

While the water is still wet, the fish rises from time to time to take a breath of air. When the film of drying water reaches the upper edge of the liquid silt lining the bottom of the reservoir, part of this silt is sucked into the hole and clogs the exit. After that, the protopter is no longer shown on the surface. Before the cork is completely dry, the fish, poking into it with its snout, compacts it from below and lifts it somewhat in the form of a cap. When dry, the cap becomes porous and allows enough air to pass through to keep sleeping fish alive. As soon as the cap hardens, the water in the burrow becomes viscous from the abundance of mucus secreted by the protopter. As the soil dries up, the water level in the hole drops, and eventually the vertical passage turns into an air chamber, and the fish, bending over in half, freezes in the lower, expanded part of the hole. A slimy cocoon is formed around it, tightly adhering to the skin, in the upper part of which there is a thin passage through which air penetrates to the head. In this state, the protopter waits for the next rainy period, which occurs in 6–9 months. Under laboratory conditions, the protopters were kept in hibernation for more than four years, and at the end of the experiment they woke up safely.

When the reservoir begins to dry up, lepidosiren digs a hole at the bottom, in which it settles in the same way as the protopters, and clogs the entrance with a cork from the ground. This fish does not form a cocoon - the body of a sleeping lepidosiren is surrounded by mucus moistened by groundwater. In contrast to protopters, the basis of energy metabolism during hibernation in flake is stored fat.

In 2-3 weeks after the new flooding of the reservoir, lepidosiren start breeding. The male digs a vertical burrow, sometimes bending horizontally towards the end. Some burrows reach 1.5 m in length and 15–20 cm in width. The fish drags leaves and grass to the end of the hole, on which the female spawns eggs 6–7 mm in diameter. The male remains in the burrow guarding the eggs and hatched fry. The mucus secreted by its skin has a coagulating effect and cleans the water in the hole from turbidity. In addition, at this time, branching skin outgrowths 5–8 cm long, abundantly supplied with capillaries, develop on its ventral fins. Some ichthyologists believe that during the period of caring for offspring, lepidosiren does not use pulmonary respiration and these outgrowths serve as additional external gills. There is also an opposite point of view - having risen to the surface and gulped fresh air, the male lepidosiren returns to the hole and through the capillaries on the outgrowths gives part of the oxygen to the water, in which eggs and larvae develop. Be that as it may, after a period of reproduction, these outgrowths resolve.

The local population appreciates the tasty meat of the lepidoserene and intensively exterminates these fish.

Bibliography

Life of animals. Volume 4, part 1. Fish. – M.: Enlightenment, 1971.

Science and life; 1973, No. 1; 1977, No. 8.

Naumov N.P., Kartashev N.N. Zoology of vertebrates. Part 1. Lower chordates, jawless, fish, amphibians: Textbook for biologist. specialist. Univ. - M .: Higher School, 1979.

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