A type of bony fish

Lungfish are fresh water creatures, besides known as rhipidistian, they are vertebrates belonging to the order [ 1 ] Dipnoi. Lungfish are best known for retaining ancestral characteristics within the Osteichthyes, including the ability to breathe air travel, and ancestral structures within Sarcopterygii, including the presence of lobed fins with a well-developed home skeleton. lungfish represent the closest living relatives of the tetrapods. today there are only six known species of lungfish, living in Africa, South America, and Australia. The dodo record shows that lungfish were abundant since the Triassic. [ 2 ] While vicariance would suggest this represents an ancient distribution limited to the Mesozoic supercontinent Gondwana, the fossil record suggests advance lungfish had a widespread fresh water distribution and the stream distribution of modern lungfish species reflects extinction of many lineages subsequent to the separation of Pangaea, Gondwana and Laurasia. Lungfish have historically been referred to as salamanderfish, [ 3 ] but this term more often refers to Lepidogalaxias salamandroides.

Anatomy and morphology [edit ]

All lungfish show an continuous cartilaginous notochord and an extensively build up palatal dentition. Basal ( “ primitive “ ) lungfish groups may retain bare tooth and an ossify cranium, but derived lungfish groups, including all modern species, show a significant decrease in the marginal bones and a cartilaginous cranium. The bones of the skull ceiling in crude lungfish are covered in a mineralize tissue called cosmine, but in post- devonian lungfishes, the skull ceiling lies beneath the skin and the cosmine covering is lost. All modern lungfish show significant reductions and fusions of the bones of the skull roof, and the specific bones of the skull roof show no homology to the skull roof bones of ray-finned fishes or tetrapods. During the engender season, the south american lungfish develops a pair of featherlike appendages that are actually highly change pelvic fins. These fins are thought to improve boast commute around the fish ‘s eggs in its nest. [ 4 ] Through convergent evolution, lungfishes have evolved internal nostrils alike to the Tetrapods ‘ choana, [ 5 ] and a genius with certain similarities to the Lissamphibian brain ( except for the Queensland lungfish, which branched off in its own steering about 277 million years ago and has a mind resemble that of the latimeria ). [ 6 ] The dentition of lungfish is different from that of any other vertebrate group. “ Odontodes “ on the palate and lower jaws develop in a series of rows to form a fan-shaped occlusion surface. These odontodes then wear to form a consistent crush surface. In respective groups, including the mod lepidosireniformes, these ridges have been modified to form occluding blades. The modern lungfishes have a number of larval features, which suggest paedomorphosis. They besides demonstrate the largest genome among the vertebrates. modern lungfish all have an linear body with fleshy, pair pectoral and pelvic fins and a single odd caudal fin replacing the abaxial, caudal and anal fins of most fishes .

Lungs [edit ]

Protopterus dolloi) lateral pass opinion of lungs of a dissected blemish lungfish lungfish have a highly specialize respiratory system. They have a distinct sport in that their lungs are connected to the larynx and throat without a trachea. While other species of pisces can breathe breeze using modified, vascularized boast bladders, [ 7 ] these bladders are normally childlike sac, barren of complex home structure. In contrast, the lungs of lungfish are subdivided into numerous smaller air pouch, maximizing the surface sphere available for gas exchange. Most extant lungfish species have two lungs, with the exception of the australian lungfish, which has only one. The lungs of lungfish are homologous to the lungs of tetrapods. As in tetrapods and bichirs, the lungs extend from the adaxial surface of the esophagus and gut. [ 8 ] [ 9 ]

perfusion of water system [edit ]

Of extant lungfish, merely the australian lungfish can breathe through its gills without needing air from its lungs. In other species, the gills are besides atrophied to allow for adequate gas exchange. When a lungfish is obtaining oxygen from its gills, its circulatory system is configured similarly to the common pisces. The spiral valve of the conus arteriosus is exposed, the beltway arterioles of the third base and fourth gill arches ( which do not actually have gills ) are shut, the second, one-fifth and one-sixth gill arch arterioles are open, the ductus arteriosus branching off the sixth arteriole is open, and the pneumonic arteries are closed. As the water passes through the gills, the lungfish uses a buccal pump. Flow through the mouth and gills is unidirectional. blood flow through the secondary lamella is countercurrent to the water, maintaining a more constant concentration gradient .

perfusion of vent [edit ]

When breathing air, the coiling valve of the conus arteriosus closes ( minimizing the shuffle of oxygenate and deoxygenate blood ), the third base and fourth gill arches open, the second and fifth gill arches close ( minimizing the possible loss of the oxygen obtained in the lungs through the gills ), the one-sixth arteriole ‘s ductus arteriosus is closed, and the pneumonic arteries open. importantly, during air out breathe, the one-sixth gill is hush used in respiration ; deoxygenated rake loses some of its carbon dioxide as it passes through the gill before reaching the lung. This is because carbon dioxide is more soluble in water. Air flow through the mouth is tidal, and through the lungs it is bidirectional and observes “ undifferentiated pool ” diffusion of oxygen .

ecology and life history [edit ]

lungfish are omnivorous, feeding on pisces, insects, crustaceans, worms, mollusks, amphibians and plant topic. They have an intestinal coiling valve preferably than a dependable stomach. [ 10 ] african and south american lungfish are adequate to of surviving seasonal worker drying out of their habitats by burrowing into mire and estivating throughout the dry temper. Changes in physiology allow it to slow its metabolism to ampere little as 1⁄60th of the normal metabolic pace, and protein waste is converted from ammonia to less-toxic urea ( normally, lungfish excrete nitrogenous lay waste to as ammonia directly into the water ). Burrowing is seen in at least one group of dodo lungfish, the Gnathorhizidae. lungfish can be extremely durable. A Queensland lungfish at the Shedd Aquarium in Chicago was depart of the permanent populate collection from 1933 to 2017, when it was euthanized following a decline in health consistent with previous senesce. [ 11 ] A primitive australian pisces live in a San Francisco museum is believed to be the oldest life aquarium fish in the world. Methuselah is a four-foot-long ( 1.2-meter ) australian lungfish, weighing about 40 pound ( 18.1 kilogram ). [ 12 ]

evolution [edit ]

As lobe finned pisces were adapting to live in partial water or on bring, 420 million years ago during the Devonian, they seem to have split off into multiple groups. Two such branches are known to survive to the present day, the coelacanths and the lungfish. It ‘s worth noting that, despite the name “ lungfish ”, fish evolved lungs before lungfish, or even lobe-finned pisces. The coarse ancestor of lobe-finned and ray-finned fish had lungs, but in most survive branches of ray-finned pisces these evolved into float bladders used for flotation, alternatively of breathing. Some, like the bichirs, do retain their lungs, and several other traits that appear to have been coarse to lobe-finned and ray-finned pisces. [ 13 ] While the coelacanth shares many traits with reptiles, the lungfish shares particular other traits with amphibians that the coelacanth does not have. Both coelacanths and lungfishes share the category sarcopterygian with the tetrapods, which includes nation animals like reptiles, amphibians, birds, and mammals, e.g. humans. attest suggests that the tetrapods are related more closely to lungfish than to coelacanths. [ 14 ]

extant lungfish [edit ]

Queensland lungfish The Queensland lungfish, Neoceratodus forsteri, is endemic to Australia. [ 15 ] Fossil records of this group date back 380 million years, around the fourth dimension when the higher vertebrate classes were beginning to evolve. [ 16 ] Fossils of lungfish belong to the genus Neoceratodus have been uncovered in northern New South Wales, indicating that the Queensland lungfish has existed in Australia for at least 100 million years, making it a living dodo and one of the oldest be vertebrate genus on the planet. [ 16 ] [ 17 ] It is the most archaic surviving member of the ancient air-breathing lungfish ( Dipnoi ) lineages. [ 16 ] [ 18 ] The five other fresh water lungfish species, four in Africa and one in South America, are very different morphologically to N. forsteri. [ 16 ] The Queensland lungfish can live for respective days out of the water if it is observe damp, but will not survive full water depletion, unlike its african counterparts. [ 15 ] south american lungfish The south american lungfish, Lepidosiren paradoxa, is the single species of lungfish found in swamps and slow-moving waters of the Amazon, Paraguay, and lower Paraná River basins in South America. Notable as an compel air-breather, it is the sole extremity of its syndicate native to the Americas. relatively little is known about the south american english lungfish, [ 3 ] or scaly salamander-fish. [ 19 ] When young it is spotted with aureate on a black background. In the pornographic this fades to a brown or grey tinge. [ 20 ] Its tooth-bearing premaxillary and maxillary bones are fused like other lungfish. south american english lungfishes besides contribution an autostylic jaw suspension ( where the palatoquadrate is fused to the cranium ) and brawny adductor chew the fat muscles with the extant lungfish ( Dipnoi ). Like the African lungfishes, this species has an elongate, about eel-like consistency. It may reach a duration of 125 centimetres ( 4 foot 1 in ). The pectoral fins are flimsy and filamentous, while the pelvic fins are slightly larger, and set far back. The fins are connected to the shoulder by a single bone, which is a distinguish remainder from most fish, whose fins normally have at least four bones at their base ; and a cross off similarity with closely all land-dwelling vertebrates. [ 21 ] The gills are greatly reduced and basically non-functional in the adults. [ 22 ] Marbled lungfish

The marbled lungfish, Protopterus aethiopicus, is found in Africa. The marbled lungfish is legato, elongated, and cylindrical with profoundly embedded scales. The tail is very long and tapers at the end. They are the largest of the African lungfish species as they can reach a duration of up to 200 centimeter. [ 23 ] The pectoral and pelvic fins are besides very long and thin, about spaghetti-like. The newly hatched young have branched external gills much like those of newts. After 2 to 3 months the young transform ( called metamorphosis ) into the adult form, losing the external gills for gill openings. These fish have a yellow grey or pink toned ground color with colored slate-grey splotches, creating a marbling or leopard effect over the body and fins. The color model is darker along the top and light under. [ 24 ] The marbled lungfish has the largest know genome of any vertebrate, with 133 billion free-base copulate or build up blocks in its DNA double helix. The alone organisms known to have more infrastructure pairs are protist Polychaos dubium and bloom plant Paris japonica at 670 billion and 150 billion, respectively. [ 25 ] Gilled lungfish The branchiate lungfish, Protopterus amphibius is a species of lungfish found in East Africa. [ 26 ] [ 27 ] It generally reaches merely 44 centimetres ( 17 inches ) long, making it the smallest extant lungfish in the world. [ 28 ] This lungfish is consistent blue, or slate grey in color. It has small or inconspicuous black spots, and a pale grey belly. [ 29 ] west african lungfish The west african lungfish Protopterus annectens is a species of lungfish found in West Africa. [ 30 ] [ 31 ] [ 32 ] It has a outstanding snout and little eyes. Its soundbox is long and eel-like, some 9-15 times the length of the head. It has two pairs of retentive, filamentous fins. The pectoral fins have a radical fringe and are about three times the point length, while its pelvic fins are about twice the head distance. In general, three external gills are inserted buttocks to the gill slits and above the pectoral fins. It has cycloid scales embedded in the skin. There are 40-50 scales between the operculum and the anus and 36-40 around the body before the origin of the dorsal fin. It has 34-37 pairs of rib. The abaxial side is olive or brown in discolor and the ventral side is lighter, with great blackish or brown spots on the body and fins except on its belly. [ 33 ] They reach a duration of about 100 curium in the baseless. [ 34 ] Spotted lungfish The spot lungfish, Protopterus dolloi, is a species of lungfish found in Africa. specifically, it is found in the Kouilou-Niari Basin of the Republic of the Congo and Ogowe River washbasin in Gabon. It is besides found in the lower and Middle Congo River Basins. [ 35 ] Protopterus dolloi can aestivate on down by surrounding itself in a layer of dry mucus. [ 36 ] [ 37 ] It can reach a length of up to 130 curium. [ 35 ]

taxonomy [edit ]

The relationship of lungfishes to the rest of the bony fish is well understood :

  • Lungfishes are most closely related to Powichthys, and then to the Porolepiformes.
  • Together, these taxa form the Dipnomorpha, the sister group to the Tetrapodomorpha.
  • Together, these form the Rhipidistia, the sister group to the Coelacanths.

late molecular familial analyses strongly support a sister relationship of lungfishes and tetrapods ( Rhipidistia ), with Coelacanths branching slightly earlier. [ 38 ] [ 39 ] The relationships among lungfishes are importantly more unmanageable to resolve. While devonian lungfish had enough cram in the skull to determine relationships, post-Devonian lungfish are represented wholly by skull roof and tooth, as the rest of the skull is cartilaginous. additionally, many of the taxonomic group already identified may not be monophyletic. Current phylogenetic studies support the following relationships of major lungfish taxonomic group : class Osteichthyes, subclass Sarcopterygii, order Dipnoi .
In 2017, Anne Kemp, Lionel Calvin, and Guillaume Guinot found a different categorization for more derive lungfish. In this new analysis, all extant lungfish belong in the suborder Ceratodontoidei, and despite their alike appearance there is no distinct clade containing entirely Ceratodus, Neoceratodus, and their close allies .
New analyses of the relationships of the recently discovered Persephonichthys chthonica and modern lungfishes robustly places both taxa within dipterid-grade dipnoans rather than within a clade contain Late Devonian ‘ phaneropleurids ’ and park Late Paleozoic lungfishes such as Sagenodus. Monophyly of post-Devonian lungfishes is not supported and the Carboniferous-Permian taxonomic group Sagenodus is found to be incidental expense to the origins of advanced lungfishes, suggesting widespread convergence in late Paleozoic lungfishes. [ 40 ]

timeline of lungfish Genera of the devonian period [edit ]

See besides [edit ]

References [edit ]

far reading [edit ]