View source for Lungfish

{{Short description|Type of lobefinned fishes}}
{{About|the animal|the band|Lungfish (band)}}
{{Use dmy dates|date=January 2020}}
{{automatic taxobox
| name = Lungfish
| fossil_range = {{Fossil range|Early Devonian|Recent}}
| image = Neoceratodus forsteri, 2014-09-19.JPG
| image_caption = [[Queensland lungfish]]
| parent_authority = [[Per E. Ahlberg|Ahlberg]], 1991
| taxon = Dipnoi
| display_parents = 3
| authority = [[Johannes Peter Müller|J. P. Müller]], 1844
| subdivision_ranks = Living families
| subdivision = * Order [[Ceratodontiformes]]
**[[Neoceratodontidae]]
**[[Lepidosirenidae]]
**[[Protopteridae]]
Fossil taxa, see text
}}
'''Lungfish''' are freshwater vertebrates belonging to the [[Class (biology)|class]] '''Dipnoi'''.<ref>{{Cite web |title=ITIS - Report: Dipnoi |url=https://www.itis.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value=161039#null |access-date=2023-03-13 |website=www.itis.gov}}</ref> Lungfish are best known for retaining ancestral characteristics within the [[Osteichthyes]], including the ability to breathe air, and ancestral structures within [[Sarcopterygii]], including the presence of lobed fins with a well-developed internal skeleton. Lungfish represent the closest living relatives of the [[tetrapod]]s (which includes living amphibians, reptiles, birds and mammals). The mouths of lungfish typically bear tooth plates, which are used to [[Durophagy|crush hard shelled organisms]].
Today there are only six known species of lungfish, living in [[Africa]], [[South America]], and [[Australia]], though they were formerly globally distributed. The fossil record of the group extends into the Early [[Devonian]], over 410 million years ago. The earliest known members of the group were marine, while almost all post-[[Carboniferous]] representatives inhabit freshwater environments.<ref name=":0">{{Cite journal |last1=Kemp |first1=Anne |last2=Cavin |first2=Lionel |last3=Guinot |first3=Guillaume |date=2017-04-01 |title=Evolutionary history of lungfishes with a new phylogeny of post-Devonian genera |journal=Palaeogeography, Palaeoclimatology, Palaeoecology |language=en |volume=471 |pages=209–219 |bibcode=2017PPP...471..209K |doi=10.1016/j.palaeo.2016.12.051 |issn=0031-0182 |doi-access=free}}</ref>
==Etymology==
Modern Latin from the Greek δίπνοος (dipnoos) with two breathing structures, from δι- twice and πνοή breathing, breath.
==Anatomy and morphology==
All lungfish demonstrate an uninterrupted cartilaginous [[notochord]] and an extensively developed palatal dentition. [[Basal (phylogenetics)|Basal]] ("[[Primitive (phylogenetics)|primitive]]") lungfish groups may retain marginal teeth and an ossified braincase, but derived lungfish groups, including all modern species, show a significant reduction in the marginal bones and a cartilaginous braincase.  The bones of the [[skull roof]] in primitive lungfish are covered in a [[mineralized tissues|mineralized tissue]] called [[cosmine]], but in post-[[Devonian]] lungfishes, the skull roof 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 (biology)|homology]] to the skull roof bones of [[ray-finned fish]]es or [[tetrapods]]. During the breeding season, the [[South American lungfish]] develops a pair of feathery appendages that are actually highly modified pelvic fins. These fins are thought to improve gas exchange around the fish's eggs in its nest.<ref>{{cite book |author-link=Ross Piper |author=Piper, Ross |year=2007 |title=Extraordinary Animals: An encyclopedia of curious and unusual animals |publisher=[[Greenwood Press (publisher)|Greenwood Press]]}}</ref>
Through [[convergent evolution]], lungfishes have evolved internal nostrils similar to the tetrapods' [[choana]],<ref>{{cite news |url=http://scienceweek.com/2004/sa041224-3.htm |title=Evolution: On the evolution of internal nostrils (choanae) |website=Science-Week |access-date=23 September 2011 |archive-url=https://web.archive.org/web/20120320190643/http://scienceweek.com/2004/sa041224-3.htm |archive-date=20 March 2012 |url-status=dead }}</ref> and a brain with certain similarities to [[Lissamphibia]]n brain (except for the Queensland lungfish, which branched off in its own direction about 277&nbsp;million years ago and has a brain resembling that of the ''[[Latimeria]]'').<ref>{{cite journal |title=The first virtual cranial endocast of a lungfish ('' sarcopterygii'': '' dipnoi '') |journal=PLOS ONE |id=10.1371 |doi=10.1371/journal.pone.0113898 |volume=9 |year=2014 |page=e113898 |author=Clement Alice M| issue=11 |doi-access=free |pmid=25427173 |pmc=4245222 |bibcode=2014PLoSO...9k3898C }} [[File: CC-BY icon.svg|50px]]  Text was copied from this source, which is available under a [https://creativecommons.org/licenses/by/4.0/  Creative Commons Attribution 4.0 International License].</ref>
The dentition of lungfish is different from that of any other [[vertebrate]] group. "[[Odontode]]s" on the palate and lower jaws develop in a series of rows to form a fan-shaped [[Occlusion (dentistry)|occlusion]] surface. These odontodes then wear to form a uniform crushing surface. In several groups, including the modern [[lepidosireniformes]], these ridges have been modified to form occluding blades.
The modern lungfishes have a number of larval features, which suggest [[paedomorphosis]]. They also demonstrate the largest [[genome]] among the vertebrates.
Modern lungfish all have an elongate body with fleshy, paired [[pectoral fin|pectoral]] and [[pelvic fin|pelvic]] fins and a single unpaired [[caudal fin]] replacing the [[dorsal fin|dorsal]], caudal and [[anal fin|anal]] fins of most fishes.
==Lungs==
[[Image:Lungs of Protopterus dolloi.JPG|thumb|right|300 px|Lateral view of lungs of a dissected [[spotted lungfish]] (''Protopterus dolloi'')]]
Lungfish have a highly specialized [[respiratory system]]. They have a distinct feature in that their lungs are connected to the larynx and pharynx without a trachea. While other species of fish can breathe air using modified, vascularized [[gas bladder]]s,<ref name=farmer>{{citation |title=Did lungs and the intracardiac shunt evolve to oxygenate the heart in vertebrates |author=Colleen Farmer |journal=Paleobiology |year=1997 |volume=23 |issue=3 |pages=358–372 |url=http://www.biology.utah.edu/farmer/publications%20pdf/1997%20Paleobiology23.pdf |url-status=dead |archive-url=https://web.archive.org/web/20100611170942/http://www.biology.utah.edu/farmer/publications%20pdf/1997%20Paleobiology23.pdf |archive-date=11 June 2010 | doi = 10.1017/s0094837300019734 |s2cid=87285937 }}</ref> these bladders are usually simple sacs, devoid of complex internal structure. In contrast, the lungs of lungfish are subdivided into numerous smaller air sacs, maximizing the surface area 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 [[bichir]]s, the lungs extend from the ventral surface of the [[esophagus]] and gut.<ref>{{cite book |chapter-url=http://cwx.prenhall.com/bookbind/pubbooks/martini10/chapter24/custom2/deluxe-content.html |title=Human Anatomy |first=Brian |last=Wisenden |chapter=Chapter 24: The Respiratory System – Evolution Atlas |archive-url=https://web.archive.org/web/20101125095303/http://cwx.prenhall.com/bookbind/pubbooks/martini10/chapter24/custom2/deluxe-content.html |archive-date=25 November 2010  |publisher=Pearson Education, Inc |year=2003}}</ref><ref>{{cite web |url=http://people.biology.ufl.edu/sahilber/VertZooLab2007/Lab2.htm |url-status=dead |id=Lab&nbsp;2 |author=Hilber, S.A. |title=Gnathostome form & function |series=Vertebrate Zoology Lab |year=2007 |publisher=U. Florida |access-date=31 December 2010 |archive-url=https://web.archive.org/web/20110720083608/http://people.biology.ufl.edu/sahilber/VertZooLab2007/Lab2.htm |archive-date=20 July 2011 }}</ref>
===Perfusion of water===
Of extant lungfish, only the [[Australian lungfish]] can breathe through its gills without needing air from its lung. In other species, the gills are too 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 fish. The spiral valve of the [[conus arteriosus]] is open, the bypass arterioles of the third and fourth gill arches (which do not actually have gills) are shut, the second, fifth and sixth gill arch arterioles are open, the [[ductus arteriosus]] branching off the sixth arteriole is open, and the pulmonary 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 lamellae is countercurrent to the water, maintaining a more constant concentration gradient.
===Perfusion of air===
When breathing air, the spiral valve of the conus arteriosus closes (minimizing the mixing of oxygenated and deoxygenated blood), the third 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 sixth arteriole's ductus arteriosus is closed, and the pulmonary arteries open. Importantly, during air breathing, the sixth gill is still used in respiration; deoxygenated blood 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 "uniform pool" diffusion of oxygen.
==Ecology and life history==
Lungfish are [[Omnivore|omnivorous]], feeding on fish, [[insect]]s, [[crustacean]]s, [[worm]]s, [[mollusk]]s, [[amphibian]]s and plant matter. They have an [[intestinal spiral valve]] rather than a true [[stomach]].<ref>{{cite journal |doi=10.1002/ar.1091820109 |volume=182 |title=Electron microscopy of the intestine of the African lungfish, ''Protopterus aethiopicus'' |year=1975 |journal=The Anatomical Record |pages=71–89 |author=Purkerson, M.L.|issue=1 |pmid=1155792 |s2cid=44787314 }}</ref>
African and South American lungfish are capable of surviving seasonal drying out of their habitats by burrowing into mud and [[estivation|estivating]] throughout the dry season.  Changes in [[physiology]] allow it to slow its [[metabolism]] to as little as one sixtieth of the normal metabolic rate, and protein waste is converted from [[ammonia]] to less-toxic [[urea]] (normally, lungfish excrete nitrogenous waste as ammonia directly into the water).
Burrowing is seen in at least one group of fossil lungfish, the [[Gnathorhizidae]].
[[File:Granddad, Shedd Aquarium, Chicago.jpg|thumb|Granddad, Shedd Aquarium, Chicago ]]
Lungfish can be extremely long-lived. A [[Queensland lungfish]] called "Granddad"<ref name="Grauniad" /> at the [[Shedd Aquarium]] in [[Chicago]] was part of the permanent live collection from 1933 to 2017 after a previous residence at the [[Sydney Aquarium]];<ref name="Star Tribune" /> at 109 years old,<ref>{{Cite web |last=CSIRO |title=DNA reveals the true age of Granddad the lungfish |url=https://www.csiro.au/en/news/all/articles/2022/june/granddad-lungfish |access-date=2024-11-26 |website=www.csiro.au |language=en}}</ref> it was euthanized following a decline in health consistent with old age.<ref name="Star Tribune">{{cite news |url=http://www.startribune.com/chicago-aquarium-euthanizes-more-than-90-year-old-lungfish/412918113/|title=Chicago aquarium euthanizes 90&nbsp;year-old lungfish |access-date=6 February 2017 |archive-url=https://web.archive.org/web/20170207031540/http://www.startribune.com/chicago-aquarium-euthanizes-more-than-90-year-old-lungfish/412918113/ |archive-date=7 February 2017 |newspaper=Star Tribune  |url-status=dead}}</ref>
As of 2022, the oldest lungfish, and probably the oldest aquarium fish in the world is "[[Methuselah (lungfish)|Methuselah]]", an Australian lungfish {{convert|4|ft}} long and weighing around {{convert|40|lb}}. Methuselah is believed to be female, unlike [[Methuselah|its namesake]], and is estimated to be over 90 years old.<ref name="Grauniad">{{cite news |url=https://www.theguardian.com/us-news/2022/jan/26/methuselah-oldest-aquarium-fish-lives-san-francisco |title=Methuselah: Oldest aquarium fish lives in San Francisco and likes belly rubs |newspaper=The Guardian |date=26 January 2022 }}</ref>
==Evolution==
About 420 million years ago, during the [[Devonian]], the [[Most recent common ancestor|last common ancestor]] of both lungfish and the [[tetrapod]]s split into two separate evolutionary lineages, with the ancestor of the extant [[coelacanth]]s diverging a little earlier from a [[Sarcopterygii|sarcopterygian]] progenitor.<ref>[https://www.newscientist.com/article/2265127-australian-lungfish-has-largest-genome-of-any-animal-sequenced-so-far/ Australian lungfish has largest genome of any animal sequenced so far - New Scientist]</ref> ''[[Youngolepis]]'' and ''[[Diabolepis]]'', dating to 419–417 million years ago, during Early Devonian ([[Lochkovian]]), are the currently oldest known lungfish, and show that the lungfishes had adapted to a diet including hard-shelled prey ([[durophagy]]) very early in their evolution.<ref>{{Cite journal |last1=Cui |first1=Xindong |last2=Friedman |first2=Matt |last3=Qiao |first3=Tuo |last4=Yu |first4=Yilun |last5=Zhu |first5=Min |date=2022-05-02 |title=The rapid evolution of lungfish durophagy |journal=Nature Communications |language=en |volume=13 |issue=1 |pages=2390 |doi=10.1038/s41467-022-30091-3 |pmid=35501345 |pmc=9061808 |issn=2041-1723}}</ref> The earliest lungfish were marine. Almost all post-[[Carboniferous]] lungfish inhabit or inhabited freshwater environments. There were likely at least two transitions amongst lungfish from marine to freshwater habitats. The last common ancestor of all living lungfish likely lived sometime between the Late [[Carboniferous]]<ref name=":0" /> and the [[Jurassic]].<ref name=":1">{{Cite journal |last=Brownstein |first=Chase Doran |last2=Harrington |first2=Richard C |last3=Near |first3=Thomas J. |date=July 2023 |title=The biogeography of extant lungfishes traces the breakup of Gondwana |url=https://onlinelibrary.wiley.com/doi/10.1111/jbi.14609 |journal=Journal of Biogeography |language=en |volume=50 |issue=7 |pages=1191–1198 |doi=10.1111/jbi.14609 |issn=0305-0270}}</ref> Lungfish remained present in the northern [[Laurasia]]n landmasses into the [[Cretaceous]] period.<ref>{{Cite journal |last1=Frederickson |first1=Joseph A. |last2=Cifelli |first2=Richard L. |date=January 2017 |title=New Cretaceous lungfishes (Dipnoi, Ceratodontidae) from western North America |journal=Journal of Paleontology |language=en |volume=91 |issue=1 |pages=146–161 |doi=10.1017/jpa.2016.131 |s2cid=131962612 |issn=0022-3360|doi-access=free }}</ref>
==Extant lungfish==
{| class="wikitable"
|+ Extant lungfishes
|-
! Family
! Genus
! Species
|-
! [[Australian lungfish|Neoceratodontidae]]
! ''Neoceratodus''
| align=center | [[Queensland lungfish]]
|-
! [[Lepidosirenidae]]
! ''[[South American lungfish|Lepidosiren]]''
| align=center | [[South American lungfish]]
|-
! rowspan="4" |[[Protopterus|Protopteridae]]
! rowspan="4" | ''[[Protopterus]]''
| align=center | [[Marbled lungfish]]
|-
| align=center | [[Gilled lungfish]]
|-
| align=center | [[West African lungfish]]
|-
| align=center | [[Spotted lungfish]]
|}
[[File:Barramunda.jpg|thumb|Queensland lungfish]]
The [[Queensland lungfish]], ''Neoceratodus forsteri'', is [[Endemism|endemic]] to Australia.<ref name = Lake>{{cite book |last=Lake |first=John S. |title=Australian Freshwater Fishes |series=Nelson Field Guides |place=Melbourne |publisher=Thomas Nelson Australia Pty. Ltd. |year=1978 |page=12}}</ref> Fossil records of this group date back 380&nbsp;million years, around the time when the [[higher vertebrate]] classes were beginning to evolve.<ref name=Allen>{{cite book |last1=Allen |first1=G.R. |first2=S.H. |last2=Midgley |first3=M. |last3=Allen |title=Field Guide to the Freshwater Fishes of Australia. |editor1-first=Jan |editor1-last=Knight |editor2-first=Wendy |editor2-last=Bulgin |place=Perth, W.A. |publisher=Western Australia Museum |year=2002 |pages=54–55}}</ref> Fossils of lungfish belonging 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&nbsp;million years, making it a [[living fossil]] and one of the oldest living vertebrate genera on the planet.<ref name = Allen/><ref>{{Cite journal|last1=Kemp|first1=Anne|last2=Berrell|first2=Rodney|date=2020-05-03|title=A New Species of Fossil Lungfish (Osteichthyes: Dipnoi) from the Cretaceous of Australia|url=https://www.tandfonline.com/doi/full/10.1080/02724634.2020.1822369|journal=Journal of Vertebrate Paleontology|language=en|volume=40|issue=3|pages=e1822369|doi=10.1080/02724634.2020.1822369|s2cid=225133051|issn=0272-4634}}</ref> It is the most primitive surviving member of the ancient air-breathing lungfish (Dipnoi) lineages.<ref name = "Allen"/><ref name=Frentiu>{{cite journal |author1=Frentiu, F.D. |author2=Ovenden, J.R. |author3=Street, R. |title=Australian lungfish (''Neoceratodus forsteri'': Dipnoi) have low genetic variation at allozyme and mitochondrial DNA loci: A conservation alert? |series=2 |journal=Conservation Genetics |date=2001 |doi=10.1023/A:1011576116472 |pages=63–67 |volume=2|s2cid=22778872 }}</ref> The five other freshwater lungfish species, [[Protopterus|four]] in Africa and [[South American lungfish|one]] in South America, are very different morphologically to ''N. forsteri''.<ref name = Allen/> The Queensland lungfish can live for several days out of the water if it is kept moist, but will not survive total water depletion, unlike its African counterparts.<ref name = Lake/>
[[File:F de Castelnau-poissonsPl50.jpg|thumb|left|South American lungfish]]
The [[South American lungfish]], ''Lepidosiren paradoxa'', is the single species of lungfish found in [[swamp]]s and slow-moving waters of the [[Amazon River|Amazon]], [[Paraguay River|Paraguay]], and lower [[Paraná River]] [[drainage basin|basins]] in South America. Notable as an [[obligate]] air-breather, it is the sole member of its family native to the Americas. Relatively little is known about the South American lungfish,<ref name="Haeckel, Lankester, & Schmitz 1892">{{cite book |author1=Haeckel, Ernst Heinrich Philipp August |url=https://archive.org/details/TheHistoryOfCreationOrTheDevelopmentOfTheEarthAndItsInhabitants_126 |title=The History of Creation, or, the Development of the Earth and Its Inhabitants by the Action of Natural Causes |author2=Lankester, Edwin Ray |author3=Schmitz, L. Dora |publisher=D. Appleton |year=1892 |pages=289, 422 |quote=A popular exposition of the doctrine of evolution in general, and of that of Darwin, Goethe, and Lamarck in particular. From the 8th German edition by Ernst Haeckel |author1-link=Ernst Haeckel}}</ref> or ''scaly salamander-fish''.<ref>{{cite book |title=A Naturalist in Brazil |quote=The record of a year's observation of her flora, her fauna, and her people. |url=https://archive.org/details/naturalistinbraz00guen/page/399 |author=Guenther, Konrad |translator=Miall, Bernard |translator-link=Bernard Miall |year=1931 |publisher=Houghton Mifflin Company |pages=275, 399}}</ref> When immature it is spotted with gold on a black background. In the adult this fades to a brown or gray color.<ref name=SAL>{{cite web |url=http://animal-world.com/encyclo/fresh/Misc_PseudoBony/SouthAmericanLungfish.php |title=South American Lungfish |publisher=Animal World}}</ref> Its tooth-bearing [[premaxillary]] and [[maxilla]]ry bones are fused like other lungfish. South American lungfishes also share an autostylic jaw suspension (where the [[palatoquadrate]] is fused to the [[cranium]]) and powerful adductor jaw muscles with the extant lungfish (Dipnoi). Like the [[African lungfish]]es, this species has an elongate, almost eel-like body. It may reach a length of {{convert|125|cm|ftin}}. The [[pectoral fin]]s are thin and threadlike, while the pelvic fins are somewhat larger, and set far back. The fins are connected to the shoulder by a single bone, which is a marked difference from most fish, whose fins usually have at least four bones at their base; and a marked similarity with nearly all land-dwelling vertebrates.<ref>"Your Inner Fish" Neil Shubin, 2008,2009,Vintage, p.33</ref> They have the lowest aquatic respiration of all extant lungfish species,<ref>[https://pubmed.ncbi.nlm.nih.gov/11691604/ The differential cardio-respiratory responses to ambient hypoxia and systemic hypoxaemia in the South American lungfish, Lepidosiren paradoxa]</ref> and their gills are greatly reduced and essentially non-functional in the adults.<ref name=EoF>{{cite book |editor=Paxton, J.R. |editor2=Eschmeyer, W.N.|author= Bruton, Michael N.|year=1998|title=Encyclopedia of Fishes|publisher= Academic Press|location=San Diego|page= 70|isbn= 978-0-12-547665-2}}</ref>
[[File:Marbled lungfish 1.jpg|thumb|upright|Marbled lungfish]]
The [[marbled lungfish]], ''Protopterus aethiopicus'', is found in Africa. The marbled lungfish is smooth, elongated, and cylindrical with deeply embedded [[scale (zoology)|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 length of up to 200&nbsp;cm.<ref name = fishbase>[http://www.fishbase.org/Summary/SpeciesSummary.php?id=8734 Fishbase.org]</ref> The pectoral and pelvic fins are also very long and thin, almost 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 yellowish gray or pinkish toned ground color with dark slate-gray splotches, creating a marbling or leopard effect over the body and fins. The color pattern is darker along the top and lighter below.<ref>{{cite web|url=http://animal-world.com/encyclo/fresh/Misc_PseudoBony/LeopardLungfish.php|title=Marbled Lungfish|author=Animal-World|work=Animal World}}</ref> The marbled lungfish's [[genome]] contains 133 billion [[base pairs]], making it the largest known genome of any [[vertebrate]]. The only [[organism]]s known to have more base pairs are the [[protist]] ''[[Polychaos dubium]]'' and the flowering plant ''[[Paris japonica]]'' at 670 billion and 150 billion, respectively.<ref>{{cite journal | author = IJ Leitch | date = 13 June 2007 | title = Genome sizes through the ages | journal = Heredity | volume = 99 | pages = 121–122 | publisher = Nature Publishing Group | issn = 0018-067X | doi = 10.1038/sj.hdy.6800981 | pmid = 17565357 | issue=2| s2cid = 5406138 }}</ref>
[[File:Protopterus amphibius.png|thumb|left|Gilled lungfish]]
The [[gilled lungfish]], ''Protopterus amphibius'' is a species of lungfish found in [[East Africa]].<ref>[http://www.eol.org/pages/217169 EOL.org]  (Retrieved 19 February 2010.)</ref><ref>[http://www.fishbase.org/summary/Speciessummary.php?id=8735 Fishbase.org] (Retrieved 19 February 2010.)</ref> It generally reaches only {{convert|44|cm|in|0|abbr=off}} long, making it the smallest [[Extant taxon|extant]] lungfish in the world.<ref>[http://www.primitivefishes.com/Gilled%20African%20Lungfish.htm Primitive Fishes.com] {{webarchive|url=https://web.archive.org/web/20081211022858/http://www.primitivefishes.com/Gilled%20African%20Lungfish.htm |date=11 December 2008 }} Retrieved 19 February 2010.</ref> This lungfish is uniform blue, or slate grey in colour. It has small or inconspicuous black spots, and a pale grey belly.<ref>[http://www.fishbase.org/summary/Speciessummary.php?id=8735 Fishbase.org] (Retrieved 25 September 2010.)</ref>
[[File:LepidosirenFord.jpg|thumb|West African lungfish]]
The [[west African lungfish]], ''Protopterus annectens'', is a species of lungfish found in West Africa.<ref>[http://www.eol.org/pages/217169 EOL.org]  (Retrieved 13 May 2010.)</ref><ref>[http://www.fishbase.org/summary/Speciessummary.php?id=8735 Fishbase.org] (Retrieved 13 May 2010.)</ref><ref>{{cite web|url=http://fishbase.org/Summary/SpeciesSummary.php?id=2384|title=Protopterus annectens, West African lungfish : fisheries, aquaculture|work=FishBase}}</ref> It has a prominent [[snout]] and small [[eye]]s. Its body is long and [[eel|eel-like]], some 9–15 times the length of the head. It has two pairs of long, filamentous [[Fish fin|fins]]. The [[pectoral fin]]s have a basal fringe and are about three times the head length, while its [[pelvic fin]]s are about twice the head length. In general, three external [[Fish gill|gills]] are inserted [[posterior (anatomy)|posterior]] to the [[gill slit]]s and above the pectoral fins. It has [[cycloid scale]]s embedded in the skin. There are 40–50 scales between the [[operculum (fish)|operculum]] and the [[anus]] and 36–40 around the body before the origin of the [[dorsal fin]]. It has 34–37 pairs of [[rib]]s. The [[Dorsum (anatomy)|dorsal]] side is olive or brown in color and the [[ventral]] side is lighter, with great blackish or brownish spots on the body and fins except on its belly.<ref>{{cite encyclopedia|url=http://www.eol.org/pages/1298995?text_id=6652736|title=West African Lungfish (Protopterus annectens annectens) - Information on West African Lungfish - Encyclopedia of Life|encyclopedia=Encyclopedia of Life}}{{Dead link|date=March 2020 |bot=InternetArchiveBot |fix-attempted=yes }}</ref> They reach a length of about 100&nbsp;cm in the wild.<ref>[http://www.primitivefishes.com/pannectens.htm Primitivefishes.com (Retrieved May 13, 2010.)] {{webarchive|url=https://web.archive.org/web/20101011104325/http://www.primitivefishes.com/pannectens.htm |date=11 October 2010 }}</ref>
[[File:Protopterus dolloi Boulenger2.jpg|thumb|left|Spotted lungfish]]
The [[spotted lungfish]], ''Protopterus dolloi'', is a species of lungfish found in Africa. Specifically, it is found in the [[Kouilou-Niari River|Kouilou-Niari]] Basin of the [[Republic of the Congo]] and [[Ogowe]] River basin in [[Gabon]]. It is also found in the lower and Middle [[Congo River Basin]]s.<ref name="Fishbase.org">[http://www.fishbase.org/summary/speciessummary.php?id=8736 Fishbase.org]</ref> ''Protopterus dolloi'' can [[aestivate]] on land by surrounding itself in a layer of dried [[mucus]].<ref>Brien, P. (1959). Ethologie du Protopterus dolloi(Boulenger) et de ses larves. Signification des sacs pulmonaires des Dipneustes. Ann. Soc. R. Zool. Belg. 89, 9–48.</ref><ref>Poll, M. (1961). Révision systématique et raciation géographique des Protopteridae de l’Afrique centrale. Ann. Mus. R. Afr. Centr. Sér. 8. Sci. Zool. 103, 3–50.</ref> It can reach a length of up to 130&nbsp;cm.<ref name="Fishbase.org"/>
{{Clear}}
==Taxonomy==
[[File:Ceratodus.jpg|thumb|right|Illustration of ''[[Ceratodus (genus)|Ceratodus]]'' by [[Heinrich Harder]]]]
{{more citations needed section|type=animal|auto=yes|date=October 2020}}
The relationship of lungfishes to the rest of the [[Osteichthyes|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 [[coelacanth]]s.
Recent molecular genetic analyses strongly support a sister relationship of lungfishes and tetrapods ([[Rhipidistia]]), with coelacanths branching slightly earlier.<ref>{{cite journal |title=The African coelacanth genome provides insights into tetrapod evolution |journal=Nature |date=18 April 2013 |doi=10.1038/nature12027 |pmid=23598338 |volume=496 |issue=7445 |pages=311–316 |pmc=3633110 |last1=Amemiya |first1=Chris T. |last2=Alföldi |first2=Jessica |last3=Lee |first3=Alison P. |last4=Fan |first4=Shaohua |last5=Philippe |first5=Hervé |last6=MacCallum |first6=Iain |last7=Braasch |first7=Ingo |last8=Manousaki |first8=Tereza |last9=Schneider |first9=Igor |last10=Rohner |first10=Nicolas |last11=Organ |first11=Chris |last12=Chalopin | first12 = Domitille | last13 = Smith |first13=Jeramiah J. |last14=Robinson |first14=Mark |last15=Dorrington |first15=Rosemary A. |last16=Gerdol |first16=Marco |last17=Aken |first17=Bronwen |last18=Biscotti |first18=Maria Assunta |last19=Barucca |first19=Marco |last20=Baurain |first20=Denis |last21=Berlin |first21=Aaron M. |last22=Blatch |first22=Gregory L. |last23=Buonocore |first23=Francesco |last24=Burmester |first24=Thorsten |last25=Campbell |first25=Michael S. |last26=Canapa |first26=Adriana |last27=Cannon |first27=John P. |last28=Christoffels |first28=Alan |last29=De Moro |first29=Gianluca |last30=Edkins |first30=Adrienne L. |bibcode=2013Natur.496..311A |display-authors=6}}</ref><ref>{{cite journal |author1=Takezaki, N. |author2=Nishihara, H. |year=2017 |title=Support for lungfish as the closest relative of tetrapods by using slowly evolving ray-finned fish as the outgroup |journal=Genome Biology and Evolution |volume=9 |issue=1 |pages=93–101 |doi=10.1093/gbe/evw288 |pmid=28082606 |pmc=5381532}}</ref>
The relationships among lungfishes are significantly more difficult to resolve.  While Devonian lungfish had enough bone in the skull to determine relationships, post-Devonian lungfish are represented entirely by skull roofs and teeth, as the rest of the skull is [[cartilage|cartilaginous]].  Additionally, many of the taxa already identified may not be [[monophyletic]].
Phylogeny after Kemp, Cavin & Guinot, 2017<ref name=":0" />
{{Clade|{{Clade
|1=†''[[Diabolepis]]''
|2={{Clade
|1={{Clade
|1=†''[[Westollrhynchus]]''
|2={{Clade
|1=†''[[Ichnomylax]]''
|2={{Clade
|1=†''[[Dipnorhynchus]]''
|2=†''[[Speonesydrion]]''
}} }} }}
|2={{Clade
|1=†''[[Uranolophus]]''
|2={{Clade
|1=†''[[Stomiahykus]]''
|2={{Clade
|1={{Clade
|1=†''[[Iowadipterus]]''
|2=†''[[Jessenia (animal)|Jessenia]]''
}}
|2={{Clade
|1=†''[[Melanognathus]]''
|2=†''[[Tarachomylax]]''
|3={{Clade
|1=†''[[Dipterus]]''
|2={{Clade
|1=†''[[Adololopas]]''
|2={{Clade
|1={{Clade
|1={{Clade
|1=†''[[Chirodipterus australis]]''
|2=†''[[Gogodipterus]]''
}}
|2={{Clade
|1=†''[[Pillararhynchus]]''
|2=†''[[Sorbitorhynchus]]''
}} }}
|2={{Clade
|1=†''[[Chirodipterus liangchengi]]''
|2={{Clade
|1=†''[[Chirodipterus wildungensis]]''
|2={{Clade
|1=†''[[Sinodipterus]]''
|2={{Clade
|1=†''[[Rhinodipterus ulrichi]]''
|2={{Clade
|1={{Clade
|1=†''[[Soederberghia]]''
|2={{Clade
|1=†''[[Griphognathus]]''
|2=†''[[Holodipterus]]''
}} }}
|2={{Clade
|1={{Clade
|1=†''[[Andreyevichthys]]''
|2={{Clade
|1=†''[[Scaumenacia]]''
|2={{Clade
|1=†''[[Adelargo]]''
|2={{Clade
|1=†''[[Sagenodus]]''
|2={{Clade
|1=†''[[Howidipterus]]''
|2={{Clade
|1=†''[[Barwickia]]''
|2=†''[[Fleurentia]]''
}} }} }} }} }} }}
|2={{Clade
|1=†''[[Orlovichthys]]''
|2={{Clade
|1=†''[[Rhinodipterus kimberleyensis]]''
|2={{Clade
|label2=[[Ceratodontoidei]]
|1={{Clade
|1=†''[[Conchopoma]]''
|2=†''[[Ganopristodus]]''
}}
|2={{Clade
|1=†''[[Paraceratodus]]''
|2={{Clade
|1=†''[[Ferganoceratodus]]''
|2={{Clade
|label1=[[Neoceratodontidae]]
|1={{Clade
|1=†''[[Mioceratodus]]''
|2=''[[Neoceratodus]]'' (Queensland lungfish)
}}
|2={{Clade
|1=†''[[Ceratodus (genus)|Ceratodus]]''
|2={{Clade
|1={{Clade
|1=†''[[Gosfordia]]''
|2=†''[[Ptychoceratodus]]''
}}
|2={{Clade
|label1=†[[Gnathorhizidae]]
|label2=[[Lepidosirenidae]]
|1={{Clade
|1=†''[[Gnathorhiza]]''
|2=†''[[Persephonichthys]]''
}}
|2={{Clade
|1=''[[Lepidosiren]]'' (South American lungfish)
|2=''[[Protopterus]]'' (African lungfish)
}} }} }} }} }} }} }} }} }} }} }} }} }} }} }} }} }} }} }} }} }} }} }} }} }}|style=font-size:85%; line-height:85%}}
Cladogram after Brownstein et al. 2023<ref name=":1" />
{{clade
|1={{clade
|1=†''[[Chirodipterus]]''
|2=†''[[Dipterus]]''
}}
|2={{clade
|1={{clade
|1=†''[[Ctenodus]]''
|2=†''[[Sagenodus]]''
}}
|2={{clade
|1={{clade
|1=†''[[Conchopoma]]''
|2=†''[[Ganopristodus]]''
}}
|2={{clade
|1={{clade
|1=†''[[Gnathorhiza]]''
|2=†''[[Persephonichthys]]''
}}
|2={{clade
|1=†''Ceratodus''
|2={{clade
|1=†''[[Gosfordia]]''
|2={{clade
|1=†''[[Paraceratodus]]''
|2={{clade
|1=†''[[Ptychoceratodus]]''
|2={{clade
|1={{clade
|1=†''[[Ferganoceratodus]]''
|2={{clade
|1=†''[[Mioceratodus]]''
|2=''[[Neoceratodus]]'' (Queensland lungfish)
}}}}
|2={{clade
|1=''[[Lepidosiren]]'' (South American lungfish)
|2=''[[Protopterus]]'' (African lungfish)
}}}}}}}}}}}}}}}}}}|label=}}
==See also==
* ''[[Ceratodus (genus)|Ceratodus]]''
* ''[[Lepidogalaxias salamandroides]]''
* ''[[Polypteridae]]''
==References==
{{Reflist|25em}}
==Further reading==
* {{cite journal |author1=Ahlberg, P.E. |author2=Smith, M.M. |author3=Johanson, Z. |year=2006 |title=Developmental plasticity and disparity in early ''dipnoan'' (lungfish) dentitions |journal=Evolution and Development |volume=8 |issue=4 |pages=331–349 |doi=10.1111/j.1525-142x.2006.00106.x|pmid=16805898 |s2cid=28339324 }}
* {{cite encyclopedia |editor=Palmer, Douglas |title=The Simon & Schuster Encyclopedia of Dinosaurs & Prehistoric Creatures, A visual who's who of prehistoric life. |page=45 |place=Great Britain |publisher=Marshall Editions Developments Limited |year=1999}}
* {{cite journal |author1=Schultze, H.P. |author2=Chorn, J. |year=1997 |title=The Permo-Carboniferous genus ''Sagenodus'' and the beginning of modern lungfish |journal=Contributions to Zoology |volume=61 |issue=7 |pages=9–70|doi=10.1163/18759866-06701002 |doi-access=free }}
* {{cite journal |last=Sepkoski |first=Jack |title=A compendium of fossil marine animal genera |journal=Bulletins of American Paleontology |volume=364 |page=560 |year=2002 |url=http://strata.ummp.lsa.umich.edu/jack/showgenera.php?taxon=611&rank=class |access-date=17 May 2011 |url-status=dead |archive-url=https://web.archive.org/web/20090220223520/http://strata.ummp.lsa.umich.edu/jack/showgenera.php?taxon=611&rank=class |archive-date=20 February 2009 }}
==External links==
{{Wikispecies|Dipnoi}}
{{Wikibooks|Dichotomous Key|Dipnoi}}
* {{cite web |url=http://annekempslungfish.com/index.html |archive-url=https://web.archive.org/web/20140802224356/http://annekempslungfish.com/index.html |url-status=dead |archive-date=2014-08-02 |first=Anne, Dr. |last=Kemps |title=Lungfish Information site}}
* {{cite web |url=http://www.palaeos.com/Vertebrates/Units/140Sarcopterygii/140.500.html |archive-url=https://web.archive.org/web/20060313152753/http://www.palaeos.com/Vertebrates/Units/140Sarcopterygii/140.500.html |url-status=dead |archive-date=2006-03-13 |title=Dipnoiformes |website=Palaeos.com}}
* {{cite web |url=http://www.ucmp.berkeley.edu/vertebrates/sarco/dipnoi.html |title=Dipnoi |publisher=University of California Museum of Paleontology}}
* {{cite web |url=http://www.tellapallet.com/tree_of_life.htm |archive-url=https://web.archive.org/web/20090123062500/https://www.tellapallet.com/tree_of_life.htm |title=Tree of life illustration showing lungfish's relation to other organisms |url-status=dead |archive-date=2009-01-23 |website=tellapallet.com}}
* {{cite web |url=https://www.youtube.com/watch?v=D1UKHimLZao | archive-url=https://ghostarchive.org/varchive/youtube/20211118/D1UKHimLZao| archive-date=2021-11-18 | url-status=live|title=Lungfish video |website=YouTube}}{{cbignore}}
{{Chordata}}
{{Sarcopterygii}}
{{Sarcopterygian genera|R.|state=autocollapse}}
{{diversity of fish}}
{{Taxonbar|from=Q168422}}
{{Authority control}}
[[Category:Lungfish| ]]
[[Category:Articles which contain graphical timelines]]
[[Category:Extant Early Devonian first appearances]]