Editing Sea turtle (section)

===Osmoregulation===

Sea turtles maintain an internal environment that is [[hypotonic]] to the ocean. To maintain hypotonicity they must excrete excess salt ions.<ref>{{cite journal |author1=Nicolson, S.W. |author2=P.L. Lutz |year=1989 |url=http://jeb.biologists.org/content/144/1/171.full.pdf |title=Salt gland function in the green sea turtle ''Chelonia mydas'' |journal=Journal of Experimental Biology |volume=144 |issue=1 |pages=171–184|doi=10.1242/jeb.144.1.171 |doi-access=free |bibcode=1989JExpB.144..171N }}</ref> Like other marine reptiles, sea turtles rely on a specialized gland to rid the body of excess salt, because reptilian kidneys cannot produce urine with a higher ion concentration than sea water.<ref name="ncbi">{{cite journal |author1=Reina RD |author2=Jones TT |author3=Spotila JR |title=Salt and water regulation by the leatherback sea turtle ''Dermochelys coriacea'' |journal=Journal of Experimental Biology |volume=205 |issue=13 |pages=1853–60 |date=July 2002  |doi=10.1242/jeb.205.13.1853 |pmid=12077161 |bibcode=2002JExpB.205.1853R |url=http://jeb.biologists.org/cgi/pmidlookup?view=long&pmid=12077161|url-access=subscription }}</ref> All species of sea turtles have a [[lachrymal gland]] in the orbital cavity, capable of producing tears with a higher salt concentration than sea water.<ref>{{cite journal |author1=Schmidt-Nielsen K |author2=Fange R |year=1958 |title=Salt glands in marine reptiles |journal=Nature |volume=182 |issue=4638 |pages=783–5 |doi=10.1038/182783a0|bibcode=1958Natur.182..783S |s2cid=4290812 }}</ref>

Leatherback sea turtles face an increased osmotic challenge compared to other species of sea turtle, since their primary prey are jellyfish and other gelatinous plankton, whose fluids have the same concentration of salts as sea water. The much larger lachrymal gland found in leatherback sea turtles may have evolved to cope with the higher intake of salts from their prey. A constant output of concentrated salty tears may be required to balance the input of salts from regular feeding, even considering leatherback sea turtle tears can have a salt ion concentration almost twice that of other species of sea turtle.<ref>{{cite journal | last1 = Hudson | first1 = D.M. | last2 = Lutz | first2 = P.L. | year = 1986 | title = Salt gland function in the leatherback sea turtle, ''Dermochelys coriacea'' | journal = Copeia | volume = 1986 | issue = 1| pages = 247–249 | jstor=1444922 | doi=10.2307/1444922}}</ref>
[[Image:Young Honu-Kahala.png|thumb|Immature Hawaiian green sea turtle in shallow waters]]
[[File:Sea turtles bask in the Papahānaumokuākea Marine National Monument.png|thumb|Sea turtles basking in the [[Papahānaumokuākea Marine National Monument]] in the [[Northwestern Hawaiian Islands]].]]
Hatchlings depend on drinking sea water immediately upon entering the ocean to replenish water lost during the hatching process.  Salt gland functioning begins quickly after hatching, so that the young sea turtles can establish ion and water balance soon after entering the ocean. Survival and physiological performance hinge on immediate and efficient hydration following emergence from the nest.<ref name="ncbi" />