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lungfish

lungfish, common name for any of a group of fish belonging to the families Ceratodontidae, Lepidosirenidae, and Protopteridae, found in the rivers of Australia, South America, and Africa, respectively. Like the lobefins (coelocanths), the lungfishes are ancestrally related to the four-footed land animals. Fossil lungfish have been found in the United States, Europe, and India. Of the living specimens, the most primitive is an Australian species, a stout-bodied 5-ft (150-cm) fish with paired fins set on short stumps. The function of it single lung (all other species have two) is not clearly understood. The fins of other lungfishes have become long, wispy sense organs, and they are in general more eellike in appearance. Lungfish feed on snails and plants, storing quantities of fat for sustenance during hibernation.

Best-known are the African species, which hibernate in hard clay balls during the dry season. They line their retreat with a waterproof membrane of dried mucus and apply their mouths to tubes of this material that serve as airshafts from the cocoons to the surface of the ground. They can remain dormant in this manner for up to three years. In water, the African lungfishes breathe with gills.

The South American loalach is totally dependent on air and will drown if held underwater. Its eggs are laid in a long tunnel at the bottom of a swamp and are guarded by the male, which sprouts red filamental gills from his pelvic fins. The young are also equipped with temporary external gills.

Lungfish are classified in the phylum Chordata, subphylum Vertebrata, class Sarcopterygii, order Ceratodontiformes, family Ceratodontidae, and order Lepidosireniformes, families Lepidosirenidae and Protopteridae.

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Dipnoi

Dipnoi (Dipneusti; class Osteichthyes) Literally, ‘double breathing’. Often ranked as a subclass, the group includes the extant lung-fish and their fossil relatives (e.g. the Middle Devonian Dipterus and the Triassic Ceratodus). Early forms have an elongated body, a well-ossified internal skeleton, heterocercal tail, fleshy-lobed fins, and cosmoid scales. Teeth are absent, but one of the commonest fossils is the broad fan-shaped tooth plate that served for shearing and crushing small invertebrates. Dipnoans first appear in Lower Devonian rocks and were common in freshwater habitats in the late Palaeozoic and the Triassic; thereafter their fossil remains are very sparse. There are just three surviving genera (Neoceratodus, Protopterus, and Lepidosiren), all tropical.

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Dipnoi

Dipnoi A subclass or order of bony fishes that contains the lungfishes, which have lungs and breathe air. They are found in Africa, Australia, and South America, where they live in freshwater lakes and marshes that tend to become stagnant or even dry up in summer. They survive in these conditions by burrowing into the mud, leaving a small hole for breathing air, and entering a state of aestivation, in which they can remain for six months or more. The Dipnoi date from the Devonian era (408–360 million years ago) and share many features with the modern Amphibia.

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Dipneusti

Dipneusti (Dipnoi; class Osteichthyes, Often ranked as a subclass, the group that includes the extant lungfish and their fossil relatives. The lungfish are an order of bony fish (Osteichthyes) in the subclass Choanichthyes (Sarcopterygii), or fleshy-finned fish. They first appear in early Devonian rocks and were common in freshwater habitats in the late Palaeozoic and Triassic. Thereafter their fossil remains are very sparse and now there are just three surviving types, all in the tropics. See also CERATODIFORMES.

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lungfish

lungfish Elongated fish from which the first amphibians developed, found in shallow freshwater and swamps in Africa, South America, and Australia. It has primitive lungs, and, during a dry season, the various species can breath air or survive total dehydration by burrowing into the mud and enveloping themselves in a mucous cocoon. Order Dipnoi.

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lungfish

lung·fish / ˈləngˌfish/ • n. (pl. same or -fishes) an elongated freshwater fish (families Ceratodontidae, Lepidosirenidae, and Protopteridae) with one or two sacs that function as lungs, enabling it to breathe air. It can estivate in mud for long periods to survive drought.

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lungfish

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Dipneusti

Dipneusti See DIPNOI.

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Dipnoi

Dipnoi See DIPNEUSTI.

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lungfish

lungfish See Dipnoi.

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lungfish

lungfish •raffish • damselfish •catfish, flatfish •garfish, starfish •redfish •elfish, selfish, shellfish •devilfish •crayfish, waifish •stiffish • kingfish • jellyfish •killifish • filefish • pipefish •white fish •offish, standoffish •codfish • dogfish • rockfish • crawfish •swordfish •blowfish, oafish •goldfish •bonefish, stonefish •wolfish •huffish, roughish, toughish •mudfish • monkfish • cuttlefish •lungfish • lumpfish • spearfish •angelfish • parrotfish • silverfish •haggish, waggish •vaguish •biggish, piggish, priggish, whiggish •doggish, hoggish •roguish, voguish •puggish, sluggish, thuggish •largish

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Lungfish

Lungfish

African And South American Lungfish

Australian Lungfish

Resources

Bony fish are divided into two major groups: rayfinned and lobe-finned fish. The lobe-finned fish are further subdivided into two orders: the lungfish, or Dipnoi, and the lobe-finned fish, or Crossopterygii. Although crossopterygian fish are the group that is thought to be close to the ancestors of the land vertebrates, lungfish also display many of these characteristics. In the early stages of development, lungfish resemble a frog like amphibian, providing evidence of close association with land forms. However, despite the critical presence of lungs, other features, such as the fusion of the teeth into bony plates, and the solid union of the jaw with the skull (which does not occur in early amphibians) make such a direct link with amphibians unlikely.

Lungfish have changed little over the past 400 million years, and so might be regarded as living fossils. Three living genera of lungfish are recognized today: Neoceratodus in the Mary and Burnett Rivers of southeast Queensland, Australia; Lepidosiren in the Parana´ and Amazon River systems of South America; and Protopterus in sub-Saharan Africa ranging from the Nile in Sudan southward to Senegal in West Africa to the Zambezi River system in southern Africa.

African And South American Lungfish

African and South American lungfish can easily be distinguished by their appearance, but they also share many similar characters. In fact, some zoogeographers have used the close link between these two lungfishes to provide supporting evidence of an early land connection between South America and Africa. Lungfish are eel-like, with a long, narrow, tubular body and small scales well embedded in the body of the fish. Both the pectoral and pelvic fins of lungfish are elongated and somewhat threadlike. In Lepidosiren the pelvic fins are modified to function as accessory respiratory organs, with feathery margins receiving an increased blood supplythey function like a pair of gills. The primary respiratory organs of Lepidosiren are a pair of lungs with a single opening on the floor of the mouth. These lungs have furrowed walls and receive a full supply of blood. The young of both species have long, feathery, external gills located behind the head which are lost in the South American lungfish at 1.6 in (4 cm) in length, and at 5.9 in (15 cm) in the African lungfish. Both South American and African species reach a length of 3.3-6.6 ft (1-2 m).

When lungfish are in water, they breathe air by rising to the surface and sticking the tips of their nasal opening and mouth out of the water, so as to empty their lungs and take in fresh air. In most fish, the nostrils are pouchlike. However, the jaw construction of the lungfish is modified so that there is an opening from the nasal sac to the inside of the mouth. This internal nostril allows the fish to breathe air at the surface without opening its mouth and swallowing water. Because lungfish breathe by lungs instead of gills, air is essential for their survival; if lungfish are forced to remain underwater, they will drown.

Lungfish live in areas with temporary water bodies, such as shallow swamps, the stagnant

backwaters of river courses, and small creeks. These areas are prone to dry out during the dry season. As the water recedes, lungfish burrow into the mud, forming a hollow at the end of the tunnel. The lungfish curl up, tail over head, keeping the nostrils clear of dust and dirt, and secrete a mucous cocoon. Air enters the burrow through a small hole at the top of the dried mud. Lungfish are able to remain in a period of aestivation (dormancy) for the duration of the dry season and have been known to survive as long as four years, although usually a year is all that is necessary. During the aestivation period, lungfish experience a drop in their metabolism and obtain adequate nutrition from the stored fat in their tail.

Breeding takes place in the wet season following the reestablishment of the water bodies they inhabit. The male of the South American lungfish guards the eggs during the period of incubation and hatching.

Australian Lungfish

The Australian lungfish is the most primitive of the modern lungfish and has changed little over the past several million years. The body is long, slim, and has very large scales, and broad, flipper-like pectoral and pelvic fins. A dorsal fin is lacking. The tail of the Australian lungfish is most unusual, and consists of a rim of fin material around the rear end of the body.

The Australian lungfish has four big teeth which look as though they have grown together into fan-shaped crushing plates somewhat resembling a roosters comb. Prior to the discovery of the first Australian lungfish around 1869, large teeth of this type had only been found in the fossil record. These teeth are an efficient adaptation for shearing and crushing. Neoceratodus is a carnivorous fish, feeding on small mollusks, crustaceans, and other aquatic invertebrates. Its paddle like fins are unsuitable for crawling; however, the lungfish can stand on these appendages, using them like legs underwater. The Australian lungfish has a single lung located above the gut which is slightly less developed than the lungs of the African and South American species.

Also known as the Burnett salmon, the Australian lungfish inhabits rivers that generally remain as permanent watercourses and do not dry out periodically, although the dissolved oxygen content does vary considerably. This lungfish uses its gills more than the other two types of lungfishes and, in well-oxygenated water, does not need to return to the surface for air. However, this species is less tolerant of poor water quality and can efficiently use its lung to breathe fresh air from the atmosphere when necessary. The Australian lungfish does not aestivate in a cocoon of mud like the African lungfish. Instead the Australian lungfish spawns in shallow water in the fall, laying its eggs on water plants. The native Australians call this lungfish dyelleh.

KEY TERMS

Aestivation A state of dormancy or torpor during the dry season, a period of drought.

Dorsal Of, toward, on, in, or near the back.

Pectoral Pertaining to the breast or chest.

Pelvic Of, in, near, or pertaining to the pelvis; in fish, either of a pair of lateral hind fins; also called the ventral fin.

Zoogeographer A person making the biological study of the geographical distribution of animals.

Resources

BOOKS

Bemis, W.E., W.W. Burggren, and N.E. Kemp. The Biology and Evolution of Lungfishes. New York: Alan R. Liss, 1987.

Graham, J.B. Air-breathing Fishes. San Diego: Academic Press, 1997.

Nelson, Joseph S. Fishes of the World. 4th ed. New York: John Wiley & Sons, 2006.

Whiteman, Kate. World Encyclopedia of Fish and Shellfish. New York: Lorenz Books, 2000.

Betsy A. Leonard

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Lungfish

Lungfish

Bony fish are divided into two major groups: rayfinned and fleshy-finned fish . The fleshy-finned fish are further subdivided into two orders: the lungfish, or Dipnoi, and the lobe-finned fish, or Crossopterygii. Although crossopterygian fish are the group that is thought to be close to the ancestors of the land vertebrates , lungfish also display many of these characteristics. In the early stages of development, lungfish resemble a frog-like amphibian, providing evidence of close association with land forms. However, despite the critical presence of lungs, other features, such as the fusion of the teeth into bony plates, and the solid union of the jaw with the skull (which does not occur in early amphibians ) make such a direct link with amphibians unlikely.

Lungfish have changed little over the past 400 million years, and so might be regarded as living fossils. Three living genera of lungfish are recognized today: Neoceratodus in the Mary and Burnett Rivers of southeast Queensland, Australia ; Lepidosiren in the ParanNBSP and Amazon River systems of South America ; and Protopterus in sub-Saharan Africa ranging from the Nile in Sudan southward to Senegal in West Africa to the Zambezi River system in southern Africa.


African and South American lungfish

African and South American lungfish can easily be distinguished by their appearance, but they also share many similar characters. In fact, some zoogeographers have used the close link between these two lungfishes to provide supporting evidence of an early land connection between South America and Africa. Lungfish are eel-like, with a long, narrow, tubular body and small scales well embedded in the body of the fish. Both the pectoral and pelvic fins of lungfish are elongated and somewhat threadlike. In Lepidosiren the pelvic fins are modified to function as accessory respiratory organs, with feathery margins receiving an increased blood supply—they function like a pair of gills. The primary respiratory organs of Lepidosiren are a pair of lungs with a single opening on the floor of the mouth. These lungs have furrowed walls and receive a full supply of blood. The young of both species have long, feathery, external gills located behind the head which are lost in the South American lungfish at 1.6 in (4 cm) in length, and at 5.9 in (15 cm) in the African lungfish. Both South American and African species reach a length of 3.3-6.6 ft (1-2 m).

When lungfish are in water , they breathe air by rising to the surface and sticking the tips of their nasal opening and mouth out of the water, so as to empty their lungs and take in fresh air. In most fish, the nostrils are pouchlike. However, the jaw construction of the lungfish is modified so that there is an opening from the nasal sac to the inside of the mouth. This internal nostril allows the fish to breathe air at the surface without opening its mouth and swallowing water. Because lungfish breathe by lungs instead of gills, air is essential for their survival; if lungfish are forced to remain underwater, they will drown.

Lungfish live in areas with temporary water bodies, such as shallow swamps, the stagnant backwaters of river courses, and small creeks. These areas are prone to dry out during the dry season. As the water recedes, lungfish burrow into the mud, forming a hollow at the end of the tunnel. The lungfish curl up, tail over head, keeping the nostrils clear of dust and dirt, and secrete a mucous cocoon. Air enters the burrow through a small hole at the top of the dried mud. Lungfish are able to remain in a period of aestivation (dormancy) for the duration of the dry season and have been known to survive as long as four years, although usually a year is all that is necessary. During the aestivation period, lungfish experience a drop in their metabolism and obtain adequate nutrition from the stored fat in their tail. Breeding takes place in the wet season following the reestablishment of the water bodies they inhabit. The male of the South American lungfish guards the eggs during the period of incubation and hatching.


Australian lungfish

The Australian lungfish is the most primitive of the modern lungfish and has changed little over the past several million years. The body is long, slim, and has very large scales, and broad, flipper-like pectoral and pelvic fins. A dorsal fin is lacking. The tail of the Australian lungfish is most unusual, and consists of a rim of fin material around the rear end of the body.

The Australian lungfish has four big teeth which look as though they have grown together into fan-shaped crushing plates somewhat resembling a rooster's comb. Prior to the discovery of the first Australian lungfish around 1869, large teeth of this type had only been found in the fossil record. These teeth are an efficient adaptation for shearing and crushing. Neoceratodus is a carnivorous fish, feeding on small mollusks , crustaceans, and other aquatic invertebrates . Its paddle-like fins are unsuitable for crawling; however, the lungfish can stand on these appendages, using them like legs underwater. The Australian lungfish has a single lung located above the gut which is slightly less developed than the lungs of the African and South American species.

Also known as the Burnett salmon , the Australian lungfish inhabits rivers that generally remain as permanent watercourses and do not dry out periodically, although the dissolved oxygen content does vary considerably. This lungfish uses its gills more than the other two types of lungfishes and, in well-oxygenated water, does not need to return to the surface for air. However, this species is less tolerant of poor water quality and can efficiently use its lung to breathe fresh air from the atmosphere when necessary. The Australian lungfish does not aestivate in a cocoon of mud like the African lungfish. Instead the Australian lungfish spawns in shallow water in the fall, laying its eggs on water plants. The native Australians call this lungfish dyelleh.


Resources

books

Whiteman, Kate. World Encyclopedia of Fish & Shellfish. New York: Lorenz Books, 2000.


Betsy A. Leonard

KEY TERMS

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Aestivation

—A state of dormancy or torpor during the dry season, a period of drought.

Dorsal

—Of, toward, on, in, or near the back.

Pectoral

—Pertaining to the breast or chest.

Pelvic

—Of, in, near, or pertaining to the pelvis; in fish, either of a pair of lateral hind fins; also called the ventral fin.

Zoogeographer

—A person making the biological study of the geographical distribution of animals.

Cite this article
Pick a style below, and copy the text for your bibliography.

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  • APA

"Lungfish." The Gale Encyclopedia of Science. . Encyclopedia.com. 12 Sep. 2018 <http://www.encyclopedia.com>.

"Lungfish." The Gale Encyclopedia of Science. . Encyclopedia.com. (September 12, 2018). http://www.encyclopedia.com/science/encyclopedias-almanacs-transcripts-and-maps/lungfish

"Lungfish." The Gale Encyclopedia of Science. . Retrieved September 12, 2018 from Encyclopedia.com: http://www.encyclopedia.com/science/encyclopedias-almanacs-transcripts-and-maps/lungfish

Learn more about citation styles

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Within the “Cite this article” tool, pick a style to see how all available information looks when formatted according to that style. Then, copy and paste the text into your bibliography or works cited list.

Because each style has its own formatting nuances that evolve over time and not all information is available for every reference entry or article, Encyclopedia.com cannot guarantee each citation it generates. Therefore, it’s best to use Encyclopedia.com citations as a starting point before checking the style against your school or publication’s requirements and the most-recent information available at these sites:

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Notes:
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