Editing Skin (section)

===Fish===
{{Further|Fish scale}}
{{One source section|date=August 2021}}

The epidermis of [[fish]] and of most [[amphibian]]s consists entirely of live [[cell (biology)|cells]], with only minimal quantities of [[keratin]] in the cells of the superficial layer.<ref name="auto">{{Cite journal |last1=Varga |first1=Joseph F. A. |last2=Bui-Marinos |first2=Maxwell P. |last3=Katzenback |first3=Barbara A. |date=2019 |title=Frog Skin Innate Immune Defences: Sensing and Surviving Pathogens |journal=Frontiers in Immunology |volume=9 |page=3128 |doi=10.3389/fimmu.2018.03128 |pmid=30692997 |pmc=6339944 |issn=1664-3224|doi-access=free }}</ref> It is generally permeable, and in the case of many [[amphibians]], may actually be a major respiratory organ.<ref>{{Cite journal |last1=Ferrie |first1=Gina M. |last2=Alford |first2=Vance C. |last3=Atkinson |first3=Jim |last4=Baitchman |first4=Eric |last5=Barber |first5=Diane |last6=Blaner |first6=William S. |last7=Crawshaw |first7=Graham |last8=Daneault |first8=Andy |last9=Dierenfeld |first9=Ellen |last10=Finke |first10=Mark |last11=Fleming |first11=Greg |date=2014 |title=Nutrition and Health in Amphibian Husbandry |journal=Zoo Biology |volume=33 |issue=6 |pages=485–501 |doi=10.1002/zoo.21180 |issn=0733-3188 |pmc=4685711 |pmid=25296396}}</ref> The [[dermis]] of [[bony fish]] typically contains relatively little of the [[connective tissue]] found in [[tetrapod]]s. <ref name="auto"/> Instead, in most species, it is largely replaced by solid, protective bony [[scale (zoology)|scales]].<ref>{{Cite web |last=Fisheries |first=NOAA |date=2022-05-03 |title=Fun Facts About Shocking Sharks {{!}} NOAA Fisheries |url=https://www.fisheries.noaa.gov/national/outreach-and-education/fun-facts-about-shocking-sharks |access-date=2022-05-11 |website=NOAA |language=en}}</ref> Apart from some particularly large dermal bones that form parts of the [[skull]], these [[scale (zoology)|scales]] are lost in [[tetrapods]], although many [[reptile]]s do have [[scale (zoology)|scales]] of a different kind, as do [[pangolin]]s.<ref>{{Cite web |title=Pangolin Fact Sheet {{!}} Blog {{!}} Nature {{!}} PBS |url=https://www.pbs.org/wnet/nature/blog/pangolin-fact-sheet/ |access-date=2022-05-11 |website=Nature |date=25 March 2020 |language=en-US}}</ref> [[Cartilaginous fish]] have numerous tooth-like [[Dermal denticle|denticles]] embedded in their skin, in place of true [[scale (zoology)|scales]].<ref>{{Cite journal |title=Shark and Ray Workbook 3-5 update 8-31 |url=https://www.floridaocean.org/sites/default/files/images/Shark%20and%20Ray%20Workbook%203-5%20update%208-31.pdf |journal=Florida Oceanographic Society}}</ref>

[[Sweat gland]]s and [[sebaceous gland]]s are both unique to [[mammals]], but other types of skin gland are found in other [[vertebrates]].{{fact|date=September 2024}} [[Fish]] typically have a numerous individual [[mucus]]-secreting skin [[cell (biology)|cells]] that aid in insulation and protection, but may also have [[poison]] [[glands]], [[photophore]]s, or [[cell (biology)|cells]] that produce a more watery, [[serous]] fluid. In [[amphibians]], the mucous cells are gathered together to form sac-like [[glands]]. Most living [[amphibians]] also possess ''granular [[glands]]'' in the skin, that secrete irritating or toxic compounds.<ref name=VB/>

Although [[melanin]] is found in the skin of many species, in the [[reptile]]s, the [[amphibians]], and [[fish]], the [[epidermis (skin)|epidermis]] is often relatively colorless. Instead, the color of the skin is largely due to [[chromatophore]]s in the [[dermis]], which, in addition to melanin, may contain [[guanine]] or [[carotenoid]] [[pigments]]. Many species, such as [[chameleon]]s and [[flounder]]s may be able to change the color of their skin by adjusting the relative size of their [[chromatophores]].<ref name=VB/>