Superorder Lungfish (Dipnoi, or Dipneustomorpha) (V. M. Makushok). Living fossils. Lungfish

When, during a six-month drought, Lake Chad in Africa reduces its area by almost one third and the muddy bottom is exposed, 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 hairpin.

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 atrium and into the right half of the ventricle, and the blood coming from the lung into 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. 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 African genus Protopterus, also from the bilung order. 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 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 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, 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 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 reports on 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.

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 atmospheric air through their nostrils2.

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.

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.

The dark protopter (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 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 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 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 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 - 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.

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.: graduate School, 1979.

Structure Lungfish reach 12 m in length, have an elongated body covered with a tile-shaped 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. The skull, unlike all other bony fish, is autostylic, cartilaginous, but complicated by chondral and integumentary bones. Secondary jaws are absent. Gill arches, including four or five pairs, cartilaginous. The shoulder girdle is well developed, cartilaginous, but covered with false bones. The pelvic girdle is 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 two hemispheres 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.

Crossword 1. What do lungfish have besides gills? 2. In what period did lungfish appear? 3. In what water bodies do they live? 4. What fish has only one lung?

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 coal), Neoceratodus forsteri (modern)

The evolution of lungfish has now been traced very fully, and we have a complete series 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

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 hairpin.

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. 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.

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 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.

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 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.

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 atmospheric air through their nostrils2.

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.

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 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.

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.

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 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, 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.

General characteristics of lungfish. gill areas coveredgill covers. In the cartilaginous skeleton, integumentary bones develop (in the region of the skull). The tail is diphycercal (see below). The intestine has a spiral valve. arterial conein the form of a coiled tube. The swim bladder is missing. In addition to the branchial, there is a pulmonary. In this feature, Dipnoi differ sharply from other fish.

Systematics. Two orders of lungfish belong to this subclass: 1) one-lung and 2) two-lung.

The first order (Monopneumones) includes the Australian flake, or ceratodus (Neoceratodus forsteri), common in the fresh waters of Queensland (Fig, A ).

Ceratod is the largest of modern lungfish, reaching a length of 1 to 2 m.

General structure of ceratodes. The valky, laterally compressed body of the ceratod ends with a diphycercal caudal fin, which is divided by the vertebral column into two almost equal halves: upper and lower.

Leather dressed in large round (cycloid) scales (without a jagged posterior edge).

The mouth is placed on the underside of the head at the anterior end of the snout; external nasal openings are covered by the upper lip; a pair of internal holes (xoan) opens to the front oral cavity. The presence of internal nasal openings stands in connection with double breathing (pulmonary and gill).

The structure of the paired limbs is remarkable: each limb has the appearance of a flipper pointed at the end.

Rice. Ceratoda skull from above (left figure) and from below (right figure).

1-cartilaginous part of the quadrate bone, with which the lower jaw articulates; 2, 3, 4 - integumentary bones of the skull roof; 5 - nostrils; 6 - eye socket; 7-praeoperculum; 8 - II rib; 9 - I rib; 10-coulterplate; 11 teeth; 12-palatopterygoideum; 13-parasphenoid; 14-interoperculum.

Skeleton

The spine is represented by a permanent chord completely not divided into separate vertebrae. Segmentation is expressed here only by the presence of cartilaginous upper processes and cartilaginous ribs.

The skull (fig.) has a wide base (platybasal type) and consists almost entirely of cartilage. In the occipital region, two small ossifications are noted; from above, the skull is covered by several superficial bones; below there is one large bone corresponding to the parasphenoid of bony fishes (Fig. , 13). The palatine cartilage adheres to the skull (autostylistic junction). The lateral parts of the skull are covered on each side by the temporal bones (squamosum = pteroticum; Fig. 2, 5). The gill cover is represented by two bones. The gill torch of the cartilaginous gill arches are absent. The shoulder girdle (Fig. 2) consists of thick cartilage, which is lined with a pair of integumentary bones. The skeleton of the paired fins is composed of the main axis, consisting of a number of cartilages, and cartilaginous rays, which support the fin lobes on each side (Fig. 2, 13). This structure of the limb is called biserial. Gegenbaur believes that the most simple type structures of the limbs should be considered a skeletal axis carrying two rows of rays. This author calls such a limb an archipterygium, and from it he produces the limbs of terrestrial vertebrates. According to the type of archipterygium, the paired fins of ceratodes are built.

Rice. 2. Skeleton of a ceratod from the side.

1,2, 3 integumentary bones of the skull roof; 4-posterior cartilaginous part of the skull; 5 -pterotjcum (squamosum); 6-operculum; 7 suborbital; 8-eye socket; 9 - shoulder girdle; 10-proximal cartilage of the pectoral fin; 11-pectoral fin; 12-pelvic belt; 13-ventral fin; 14-axis skeleton; 15 tail fin.

II Shmalgauzen (1915) admits that such an actively flexible fin with a reduced skin skeleton developed as a result of slow movement and partly swimming in heavily overgrown fresh waters.

Digestive organs of lungfish

Of the characteristic features of the flake, its teeth attract special attention. Each tooth is a plate, the convex edge of which is turned inward; tooth bears 6-7 sharp peaks directed forward. There are two pairs of such teeth: one is on the roof of the oral cavity, the other is on mandible. There can hardly be any doubt that such complex teeth occurred as a result of the fusion of individual simple conical teeth (Fig., 11).

A spiral valve stretches along the entire length of the intestine, similar to the valve found in transverse fish.

Breathing lungfish

In addition to the gills, neoceratodes have a single lung, internally divided into a number of chambers with cellular walls. The lung is located on the dorsal side of the body, but communicates with the esophagus through a canal that opens on the abdominal part of the esophagus.

The lungs of neoceratodes (and other lungfish) are similar in position and structure to the swim bladder of higher fish. In many higher fish, the inner walls of the swim bladder are smooth, while in lungfish, they are cellular. However, numerous transitions are known for this feature. So, for example, the swim bladder of bone ganoids (Lepidosteus, Amia,) has cellular inner walls. Apparently, it can definitely be considered that the lungs of Dipnoi and the swim bladder of higher fish are homologous organs.

The pulmonary arteries approach the lung, and the pulmonary veins go from it; thus, it performs a respiratory function similar to that of lacquer in terrestrial vertebrates.

Circulation

Associated with double breathing of ceratodes characteristics his circulation. In the structure of the heart, attention is drawn to the presence of a septum on the abdominal wall of the atrium, which does not completely separate the atrial cavity into the right and left halves. This septum protrudes into the venous sinus and divides its opening, directed into the atrial cavity, into two parts. There are no valves in the opening connecting the atrium to the ventricle, but the septum between the atria hangs down into the cavity of the ventricle and is partially attached to its walls. All this complex structure determines the features of the function of the heart: when the atrium and ventricle contract, the incomplete septum is pressed against the walls and for a moment isolates the right halves of both the atrium and the ventricle. The peculiar structure of the arterial cone also serves to separate the blood flow of the right and left halves of the heart. It is spirally twisted and carries eight transverse valves, with the help of which a longitudinal septum is formed in the arterial cone. It separates the left abdominal duct of the cone, through which the arterial passes, from the right dorsal, through which the venous flows.

Having become acquainted with the structure of the heart, it is easy to understand the sequence in the mechanism of blood circulation. From the pulmonary vein, the arterial enters the left side of the atrium and ventricle, going to the abdominal part of the arterial cone. Four pairs of gill vessels originate from the cone (Fig. 3). The two anterior pairs start from the ventral side of the cone and therefore receive pure arterial blood. The carotid arteries depart from these arches, supplying pure arterial blood to the head (Fig. 3, 10, 11). The two posterior pairs of branchial vessels are connected with the dorsal part of the cone and carry venous blood: the pulmonary artery branches off from the posterior fir. II, supplying venous blood for oxidation to the lungs.

Rice. 3. Scheme of arterial arches of ceratodes from the ventral side.

I, II, III, IV, V, VI-arterial arches; 7-gills; 8-efferent artery; 10- internal carotid artery; 11 - external carotid artery; 17 dorsal aorta; 19-pulmonary artery; 24-splanchnic artery.

In the right half of the heart (in the right part of the venous sinus, atrium,and then into the ventricle) all venous blood enters, which enters through the Cuvier ducts and through the inferior vena cava (see below).

This venous blood is sent to the right dorsal venous duct, into the conusaorta. Further, venous blood enters the gills, as well as into the pulmonary artery. The body of a ceratoda internal organs(except for the head department) receiveblood oxidized in the gills; the head section, as mentioned above, receives blood that has received more vigorous oxidation in the lungs. Despiteon the fact that the atrium and ventricle are completely divided into the right and left halves, thanks to a number of devices described, isolation of the pure arterial blood flow to the head is achieved (through the anterior pairs of vessels extending from the arterial cone and through the carotid arteries).

In addition to the sketch made, we point out that the appearance of the inferior vena cava, which flows into the venous sinus, is characteristic in the venous system. This vessel is absent in other fish. In addition, a special abdominal vein develops, also suitable for the venous sinus. The abdominal vein is absent in other fish, but it is well developed in amphibians.

Nervous system

For central nervous system a strong development of the forebrain is characteristic; the midbrain is relatively small, rather small.

Genitourinary organs

The kidneys represent the primary kidney (mesonephros); three pairs of pronephric tubules function only in the embryo. The ureters empty into the cloaca. Females have paired oviducts in the form of two long winding tubes that open with their anterior cones (funnel) in the body cavity near the heart. The lower ends of the oviducts, or Müllerian canals, are connected to a special papilla, which opens with an unpaired opening into the cloaca.

The male has long large testicles. In neoceratodes, numerous vas deferens lead through the primary kidney to the wolf duct, which opens into the cloaca. Note that males have well developed oviducts (Müllerian ducts).

The rest of the lungfish have some differences in the structure of the male genital organs compared to those described in neoceratodes. So, in Lepido-siren, the vas deferens (5-6 on each side) pass only through the posterior renal tubules into the common Wolffian duct. In Protopterus, one posterior tubule, which is available, has completely separated from the kidney and acquired the character of an independent excretory tract.

Ecology. Cerathodus is quite common in swampy, slow-flowing rivers. This is a sedentary sluggish fish, easily caught by a person pursuing it. At times, ceratodes rise to the surface to take air into their lungs. Air is drawn in with a characteristic sound resembling a groan. This sound is well heard on a quiet night, especially if you are on the water in a boat at that time. The pulmonary is an expedient adaptation during a period of drought, when the reservoir turns into a swamp: at that time many other fish die, and the flake seems to feel very well: at this time the pulmonary rescues the fish.

It should be noted that the predominant way of breathing in the described species is gill; in this respect it is closer to other fish than other lungfishes. He lives in the water all year round. Extracted from his natural environment the air ceratodes quickly dies.

Food consists of small animal prey - crustaceans, worms, molluscs.

Spawning from April to November. Eggs surrounded by gelatinous shells are laid between aquatic plants.

The larva of the ceratoda is devoid of external gills. Interestingly, the teeth do not merge into characteristic plates, but consist of individual sharp teeth.

Article on lungfish

Lungfish

(Dipnoi) - a subclass of fish that contains only three living genera and, in some structural features, is similar to amphibians (Amphibia). By common features D.'s organizations closely adjoin ganoid fishes (see), especially to fossil forms from Crossopterygii group, modern representative which is Polypterus (see Bishir). The signs that distinguish them from ganoid ones and bring them closer to amphibians are: in the transformation of the swim bladder into lungs; in the associated changes in the structure of the heart and nasal fossae, equipped with internal openings; in the fixed fusion of the palatine-square cartilage (palato-quadratum) with the skull (the last feature among all current fish exists only in chimeras). They live exclusively in fresh waters.

The body of D. fish (see table) is covered with tile-like overlapping cycloid scales and is provided with lateral lines; the caudal fin is quite symmetrical both outside and in relation to the posterior end of the vertebral column, continuously continues into the dorsal fin and, in addition to cartilaginous rays, also contains special so-called. horny threads (as in selachia).

Rice. 1. The pectoral fin of a barramunda (Ceratodus Forstera). 1, 2 - the first two segments of the axial ray. ++ - lateral rays, 3, 3 - horn threads. Rice. 2. Skull, shoulder girdle and pectoral fin of Protopterus. 4, 5 - vertebral bodies fused with the head skeleton. 7, 6 - their spinous processes. 8 - Superior occipital bone with a hole for the exit of the hypoglossal nerve. 9 - auditory bladder. 10 - trabeculae. 11 - fronto-parietal bone. 13 - tendon ossification. 14 - upper lattice. 15 - cartilaginous nasal capsule. 16 - preorbital process. 17, 18 - palatine-square bone. 19 - squamosal covering the square. 20, 26 - articulare connected by a ligament (22) to the hyoid bone (21), 23 - dentary (dentale). 24 - enamel strip. 25, 26 - two teeth. 27, 28 - rudimentary bones of the gill cover. I-VI - six gill arches. 29 - head rib. 30-33 - skeleton of the shoulder girdle (32-33 - cartilage, 30 and 31 - covering its bone). 34 - fibrous ligament that attaches the upper end of the shoulder girdle to the skull. 36 - the main segment of the skeleton of the pectoral fin. 1, 2, 3 - first segments of axial ray of fin ++, rudiments of lateral rays. Rice. 3. Protopterus head. External gills are visible above the pectoral fin. Rice. 4. Lower jaw of Ceratodus with dental plates. Rice. 5. Lung of Ceratodus opened to show mesh sacs (1), 5 esophagus, 2 windpipe opening, 3 pulmonary vein, 4 pulmonary artery. Rice. 6. Barramunda, Ceratodus Forsteri. Rice. 7. Protopterus annectens.

The pectoral fins lie directly behind the head; in Ceratodus, along the wide pectoral fin, a cartilaginous axis extends from one row of segments, from which, in turn, dissected cartilaginous rays extend in both directions (Fig. 1); in the rest of the D., the pectoral fins look like long cord-like appendages with one row of segments, without lateral rays (Protopterus, Fig. 2) and are not capable of serving as organs of locomotion. The pelvic fins, located far behind the pectorals, are completely similar in structure to them. According to the structure of the spinal column, D. resemble cartilaginous ganoids, especially fossils. The dorsal string, surrounded by a dense sheath, persists throughout life; vertebral bodies do not develop; the arches of the vertebrae, the ribs whose bases enter the sheath of the dorsal string, and the fin supports are more or less ossified. The cartilaginous box of the skull is covered with a few (less than in ganoid) bones, the palatine-square cartilage (palato-quadratum, Fig. 2, 17) and the square (quadratum), covered from the outside with a bone (Fig. 2, 19), merge with the cartilaginous skull. On the palate and on the ossified lower jaw, there are a pair of dental plates, seated with transverse tubercles and covered with enamel (Fig. 4). Poorly developed cartilaginous gill arches, five or six in number (Fig. 2, I-VI); operculum and rays of gill membrane rudimentary (Fig. 2, 27-28). Ceratodus 4, Lepidosiren and Protopterus have 3 pairs of gills, similar to the gills of bony fish and covered by an underdeveloped operculum, which is tightened with a fold of skin, leaving only a narrow gill opening. Protopterus also has small external gills in the form of three filiform leathery appendages above the gill opening (Fig. 3); these gills receive blood vessels from the aortic arches.

Together with the gills, the role of the respiratory organ is played by the swim bladder, which forms real lungs; in Ceratodus (Fig. 5), the swim bladder also consists of a simple, unpaired sac; in Lepidosiren and Protopterus, it is divided into two halves, opening with a short common tube into the pharynx. D.'s lungs occupy the same position in the abdominal cavity as the swim bladder of other fish (under the spine, outside the peritoneal membrane), but the windpipe opens already, as in amphibians, from the ventral side of the pharynx. It is believed that with sufficient pure water, D. breathe with gills; when at a certain time of the year the water in the reservoir deteriorates, they resort to pulmonary respiration. Inner surface lung is equipped with cells that significantly increase the respiratory surface. The atrium of the heart is divided by an incomplete septum into right and left halves, as in amphibians; this septum continues partly into the ventricle of the heart and into the arterial cone, so that there is some separation between the two currents of blood passing through the heart: between purely venous, coming from the right atrium and passing into the two posterior branchial arteries, and mixed (Ceratodus) or even pure arterial (Protopterus) current of the left atrium, going to the two anterior arteries. In Ceratodus, in a long muscular arterial cone, there are numerous valves arranged in transverse rows, similar to those in ganoid fishes; the arterial cone of Protopterus is similar to that of amphibians. The pulmonary artery comes from the last (fourth) branchial vein and therefore carries blood that has already passed through the gills; in the lungs, this blood comes into contact with air for the second time and then returns through the pulmonary veins to the heart, namely to the left half of the atrium. D.'s nasal fossae are not closed sacs, as in all fish, but at their inner end they open with a hole into the oral cavity - as in all breathing atmospheric air vertebrates; D.'s posterior nasal openings are placed at the anterior end of the mouth, in front of the palatine teeth. In the gut there is a spiral valve, as in selachia (shark fish) and ganoid. In the female genital organs, the long, stretching to the pericardium, oviducts, especially proliferating during the breeding season, resemble amphibians; at the anterior end, the oviducts open with funnel-shaped mouths into the body cavity, backwards and with one common unpaired opening open into the cloaca. Tubes similar to oviducts (Müllerian canals) exist initially in males, but later atrophy; for the exit of the seed are special ducts that develop independently of the excretory organs. In Ceratodus, two openings from the body cavity (pori abdominales, see Abdominal pore) also lead to the cloaca; Protopterus has one such opening. Fossil remains of D. are already in the Triassic. The genus Ceratodus was established for fossil fish on the basis of dental plates known from the Triassic and Jurassic formations; when the now living C. Forsteri in Australia was discovered in 1870, its dental plates were so similar to those of the Jurassic Ceratodus that the newly discovered fish was assigned to the same genus.

D. are divided into two groups:

I. One-lung, Monopneumones, which include single genus Ceratodus, two species of which are found in Australia (Fig. 6). See Barramunda.

II. Bipulmonary, Dipneumones, with two genera. Lepidosiren paradoxa, discovered in 1835 in the Amazon River, has an eel-like body with filiform paired fins, the skeleton of which consists of only one axial row of cartilages, completely without lateral rays; on the palate and on the lower jaw, a pair of dental plates; on the anterior part of the cartilaginous vomer there are two conical teeth; five gill arches with four gill slits. Gray-brown color with light spots; 1 - 1.25 meters long. Belongs to the number of very rare animals; only four specimens of this fish fell into the hands of European scientists, and over the past two decades it has not been found anymore. - Protopterus annectens (figs. 3 and 7) differs from Lepidosiren in the presence of three small external gills above the gill opening, 6 gill arches with 5 gill slits, and the presence of a small number of lateral rays on one side of the cartilaginous axis of the paired fins. Dark brown, on the underside of a lighter color with numerous indistinct gray spots; up to 2 m long. Found throughout tropical Africa, especially in the Upper Nile and Senegambia. Lives in shallow, silty waters; feeds on frogs, fish, etc., burrows deep into the silt. Its meat is eaten by the natives. In the dry season, when shallow freshwater pools dry up, Protopterus, burrowing deep into the silt, secretes a lot of mucus on the surface of the skin, which, hardening, forms a kind of cocoon around the animal, in which Protopterus remains for several months, before the onset of the rainy season; breathing at this time is done with the help of the lungs. A breathing hole is left in the wall of the cocoon opposite the mouth, from which something like a funnel sometimes goes to the animal's mouth. During hibernation, the animal does not take food, lies motionless and all vital processes fall. Such nests with fish were brought to Europe, where, after gradual soaking, Protopterus emerged from them, which then continued to live in an aquarium (Ceratodus does not burrow into the mud; to breathe atmospheric air, it comes to the surface of the water and, as is believed, resorts to this method mainly in rainy the time of the year when the water, from the applied silt and sand, becomes very dirty).

Literature. Bischoff, "Lepidosiren paradoxa" (1840); Hyrtl, "Lepidosiren paradoxa" ("Abhdl. d. böhm. Gesellsch. d. Wissenschaft", 1845); Günther, "Ceratodus" ("Philos. Transact. of the Roy. Soc.", 1871); Ayers, "Beiträge zur Anatomie und Physiologie der Dipnoer" ("Jen. Zeitschr. f. Naturw." 1884), Wiedersheim, "Zur Histologie des Dipnoerschuppen" ("Arch. f. mikr. Anat.", vol. 18, 1880 ); his, "Das Skelet u. Nervensystem v. Lepidosiren annectens" ("Morph. Studien", Fasc. I, 1880); Howes, "On the skeleton of fins of Ceratodus etc." ("Proceed. Zool. Soc.", 1887); Fulliquet, "Recherches sur le cerveau du Protopterus annectens" (1886); Van-Wijhe, "Ueber das Visceralskelet etc. der Ganoiden und v. Ceratodus". ("Niederl. Arch. f. Zool.", Vol. V, 31); Beddard, "Observations on the ovarian ovum of Protopterus" ("Proc. zool. Soc." 1886); Parker, "On the anatomy and Physiology of Protopterus annectens" (1891).

V. Fausek.

encyclopedic Dictionary F. Brockhaus and I.A. Efron. - St. Petersburg: Brockhaus-Efron. 1890-1907 .