Editing Amphibian (section)

==== Salamanders ====
[[File:Ambystoma macrodactylum 26597.JPG|thumb|alt=Larva of the long-toed salamander|Larva of the [[long-toed salamander]] <br/>(''Ambystoma macrodactylum'')]]
[[File:Ambystoma macrodactylum sigillatum, Plumas County, CA.jpg|thumb|alt=Adult of the long-toed salamander|Larva of the [[long-toed salamander]] <br/>(''Ambystoma macrodactylum'')]]
[[File:Mesotriton alpestris apuanus04.jpg|thumb|alt=Larvae of the alpine newt|Larvae of the [[alpine newt]] <br/>(''Ichthyosaura alpestris'')]]
At hatching, a typical salamander larva has eyes without lids, teeth in both upper and lower jaws, three pairs of feathery external gills, and a long tail with [[Anatomical terms of location#Dorsal and ventral|dorsal]] and [[Anatomical terms of location#Dorsal and ventral|ventral]] fins. The forelimbs may be partially developed and the hind limbs are rudimentary in pond-living species but may be rather more developed in species that reproduce in moving water. Pond-type larvae often have a pair of balancers, rod-like structures on either side of the head that may prevent the gills from becoming clogged up with sediment.<ref name=EB-Caudata/><ref>{{cite journal |author1=Valentine, Barry D. |author2=Dennis, David M. | year=1964 | title=A comparison of the gill-arch system and fins of three genera of larval salamanders, ''Rhyacotriton'', ''Gyrinophilus'', and ''Ambystoma'' | journal=Copeia | volume=1964 | issue=1 | pages=196–201 | jstor=1440850 | doi=10.2307/1440850 }}</ref> Both of these are able to breed.<ref>{{cite web |url=http://www.amphibiaweb.org/cgi-bin/amphib_query?where-genus=Ambystoma&where-species=gracile |title=''Ambystoma gracile'' |author=Shaffer, H. Bradley |year=2005 |publisher=AmphibiaWeb |access-date=November 21, 2012 |archive-date=December 26, 2012 |archive-url=https://web.archive.org/web/20121226135357/http://amphibiaweb.org/cgi-bin/amphib_query?where-genus=Ambystoma&where-species=gracile |url-status=live }}</ref> Some have larvae that never fully develop into the adult form, a condition known as [[neoteny]].<ref name=biology1994/> Neoteny occurs when the animal's growth rate is very low and is usually linked to adverse conditions such as low water temperatures that may change the response of the tissues to the hormone thyroxine.<ref>{{cite web |url=http://pages.uoregon.edu/titus/herp_old/neoteny.htm |title=Metamorphosis vs. neoteny (paedomorphosis) in salamanders (Caudata) |author=Kiyonaga, Robin R |access-date=November 21, 2012 |archive-date=August 20, 2012 |archive-url=https://web.archive.org/web/20120820014148/http://pages.uoregon.edu/titus/herp_old/neoteny.htm |url-status=live }}</ref> as well as lack of food. There are fifteen species of [[wikt:obligate|obligate]] neotenic salamanders, including species of ''[[Necturus]]'', ''[[Olm|Proteus]]'' and ''Amphiuma'', and many examples of [[wikt:facultative|facultative]] ones, such as the [[northwestern salamander]] (''Ambystoma gracile'') and the [[tiger salamander]] (''A. tigrinum'') that adopt this strategy under appropriate environmental circumstances.<ref name=biology1994>{{cite book |title=Biology of Amphibians |last=Duellman |first=William E. |author2=Trueb, Linda |author-link2=Linda Trueb|year=1994 |publisher=JHU Press |isbn=978-0-8018-4780-6 |pages=191–192 |url=https://books.google.com/books?id=CzxVvKmrtIgC&q=salamander+obligate+neoteny&pg=PA191 |access-date=October 15, 2020 |archive-date=January 26, 2021 |archive-url=https://web.archive.org/web/20210126161600/https://books.google.com/books?id=CzxVvKmrtIgC&q=salamander+obligate+neoteny&pg=PA191 |url-status=live }}</ref>

Lungless salamanders in the family Plethodontidae are terrestrial and lay a small number of unpigmented eggs in a cluster among damp leaf litter. Each egg has a large yolk sac and the larva feeds on this while it develops inside the egg, emerging fully formed as a juvenile salamander. The female salamander often broods the eggs. In the genus ''[[Ensatinas]]'', the female has been observed to coil around them and press her throat area against them, effectively massaging them with a mucous secretion.{{sfn | Stebbins | Cohen | 1995 | p=196 }}

In newts and salamanders, metamorphosis is less dramatic than in frogs. This is because the larvae are already carnivorous and continue to feed as predators when they are adults so few changes are needed to their digestive systems. Their lungs are functional early, but the larvae do not make as much use of them as do tadpoles. Their gills are never covered by gill sacs and are reabsorbed just before the animals leave the water. Other changes include the reduction in size or loss of tail fins, the closure of gill slits, thickening of the skin, the development of eyelids, and certain changes in dentition and tongue structure. Salamanders are at their most vulnerable at metamorphosis as swimming speeds are reduced and transforming tails are encumbrances on land.<ref>{{cite journal |author1=Shaffer, H. Bradley |author2=Austin, C. C. |author3=Huey, R. B. |year=1991 |title=The consequences of metamorphosis on salamander (''Ambystoma'') locomotor performance |journal=Physiological Zoology |volume=64 |issue=1 |pages=212–231 |jstor=30158520 |doi=10.1086/physzool.64.1.30158520 |s2cid=87191067 |url=https://pdfs.semanticscholar.org/35a9/f72917535be00155ac93824e53b1876583da.pdf |archive-url=https://web.archive.org/web/20200210143955/https://pdfs.semanticscholar.org/35a9/f72917535be00155ac93824e53b1876583da.pdf |url-status=dead |archive-date=2020-02-10 }}</ref> Adult salamanders often have an aquatic phase in spring and summer, and a land phase in winter. For adaptation to a water phase, prolactin is the required hormone, and for adaptation to the land phase, thyroxine. External gills do not return in subsequent aquatic phases because these are completely absorbed upon leaving the water for the first time.<ref name=EB-Caudata>{{cite encyclopedia |url=https://www.britannica.com/EBchecked/topic/100353/Caudata |title=Caudata |author=Wake, David B. |year=2012 |encyclopedia=Encyclopædia Britannica |access-date=March 26, 2012 |archive-date=May 16, 2013 |archive-url=https://web.archive.org/web/20130516165633/https://www.britannica.com/EBchecked/topic/100353/Caudata |url-status=live }}</ref>