South American lungfish
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The South American lungfish (Lepidosiren paradoxa), also known as the American mud-fish<ref>Template:Cite book page 289</ref> and scaly salamanderfish,<ref>Template:Cite book page 275</ref> 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.<ref name=fishbase>Template:FishBase</ref> Notable as an obligate air-breather, it is the sole member of its family Lepidosirenidae, although some authors also place Protopterus in the family.<ref name=":1">Template:Cite web</ref><ref name=":0">Template:Cite journal</ref> In Brazil, it is known by the indigenous language Tupi name Template:Lang, which means "snake-fish" (Template:IPA), and synonyms Template:Lang (Template:IPA), Template:Lang (Template:IPA), and Template:Lang (Template:IPA).
Taxonomy
The South American lungfish is most closely related to the African lungfishes (family Protopteridae), and both families are thought to have diverged during the Early Cretaceous. Some papers suggest classifying both Lepidosiren and Protopterus within Lepidosirenidae, though authorities continue to classify both as distinct families.<ref name=":1" /><ref name=":0" /><ref name=":2">Template:Cite journal</ref>
Description
The immature lungfish is spotted with gold on a black background; in the adult, this fades to a brown or gray color.<ref name="SAL">Animal-world: South American Lungfish.</ref> Its tooth-bearing premaxillary and maxillary bones are fused as in all Dipnoi. South American lungfish also share an autostylic jaw suspension (where the palatoquadrate is fused to the cranium) and powerful adductor jaw muscles with the other extant Dipnoi. Like the African lungfishes, this species has an elongated, almost eel-like body. It may reach a length of Template:Convert.<ref name="fishbase" /> The pectoral fins are thin and thread-like, 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> The gills are greatly reduced and essentially non-functional in the adults.<ref name="EoF">Template:Cite book</ref>
Juvenile lungfish feed on insect larvae and snails, while adults are omnivorous, adding algae and shrimp to their diets, crushing them with their heavily mineralized tooth-plates. The fish's usual habitats disappear during the dry season, so they burrow into the mud and make a chamber about Template:Convert down, leaving a few holes to the surface for air.<ref name=EoF/> During this aestivation, they produce a layer of mucus to seal in moisture, and slow their metabolism down greatly.<ref name=SAL/>
Relatively little is known about the South American lungfish. They have adapted to cope with both droughts and floods due to evolving pulmonary mechanoreceptors.<ref>Template:Cite journal</ref><ref>Template:Cite journal</ref> When the rainy season begins, they come out and begin to mate. The parents build a nest for the young, which resemble tadpoles and have four external gills. To enrich the oxygen in the nest, the male develops highly vascularized structures on his pelvic fins that release additional oxygen into the water.<ref name=EoF/> The young become air-breathing at about seven weeks. Juveniles have external threadlike gills very much like those of newts.<ref name=SAL/> Fossils of the modern species have been found between 72 and 66 mya during the Maastrichtian stage of the late Cretaceous just before the KPG extinction that killed off the non-avian dinosaurs.<ref>Template:Cite web</ref>
As of August 2024, L. paradoxa has one of the longest genomes of any species (91 billion bases, 30 times as many as the human genome).<ref name=":3">Template:Cite journal</ref> The largest genome belongs to the marbled lungfish, with 130 billion bases.<ref>Template:Cite journal</ref><ref>Template:Cite web</ref><ref>Template:Cite web</ref> PiRNA, a type of RNA that normally suppresses transposon activity, was found in low levels in the animal and is possibly among the causes of such a large genome.<ref name=":3" /><ref>Template:Cite web</ref>
See also
References
External links
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