Editing Painted turtle (section)

=== Anoxia tolerance ===
During the winter months, painted turtles become ice-locked and spend their time in either [[Hypoxia (environmental)|hypoxic]] (low oxygen) or anoxic (no oxygen) regions of the pond or lake.<ref>{{Cite journal |last=Jackson |first=D. C. |date=2002 |title=Hibernating without Oxygen: Physiological Adaptations of the Painted Turtle |journal=The Journal of Physiology |volume=543 |issue=3 |pages=731–737 |doi=10.1113/jphysiol.2002.024729 |pmid=12231634 |pmc=2290531 }}</ref> Painted turtles essentially hold their breath until the following spring when the ice melts. As a result, painted turtles rely on [[anaerobic respiration]], which leads to the production of lactic acid.<ref name=":02">{{Cite journal |last=Jackson |first=D. C. |date=2000 |title=Living without oxygen: lessons from the freshwater turtle |journal=Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology |volume=125 |issue=3 |pages=299–315 |doi=10.1016/s1095-6433(00)00160-4 |pmid=10794959 }}</ref> However, painted turtles can tolerate long periods of anoxia due to three factors: a depressed [[metabolic rate]], large [[glycogen]] stores in the liver, and sequestering lactate in the shell and releasing carbonate [[Buffer solution|buffers]] to the extracellular fluid.<ref name=":02" />

The shell of an adult painted turtle has the largest concentration of carbonate content recorded among animals.<ref>{{Cite journal |last1=Keenan |first1=S. W. |last2=Pasteris |first2=J. D. |last3=Wang |first3=A. |last4=Warren |first4=D. E. |date=2019 |title=Heterogeneous bioapatite carbonation in western painted turtles is unchanged after anoxia |journal=Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology |volume=233 |pages=74–83 |doi=10.1016/j.cbpa.2019.03.019 |pmid=30930203 |s2cid=89619510 }}</ref> This large carbonate content helps the painted turtle buffer the accumulation of lactic acid during anoxia. Both the shell and skeleton release calcium and magnesium carbonates to buffer extracellular lactic acid.<ref>{{Cite journal |last1=Jackson |first1=D. C. |last2=Crocker |first2=C. E. |last3=Ultsch |first3=G. R. |date=2000 |title=Bone and shell contribution to lactic acid buffering of submerged turtles''Chrysemys picta bellii''at 3°C |journal=American Journal of Physiology. Regulatory, Integrative and Comparative Physiology |volume=278 |issue=6 |pages=R1564–R1571 |doi=10.1152/ajpregu.2000.278.6.r1564 |pmid=10848524 |s2cid=27785024 }}</ref><ref>{{Cite journal |last=Jackson |first=D. C. |date=2004 |title=Surviving extreme lactic acidosis: the role of calcium lactate formation in the anoxic turtle |journal=Respiratory Physiology & Neurobiology |volume=144 |issue=2–3 |pages=173–178 |doi=10.1016/j.resp.2004.06.020 |pmid=15556100 |s2cid=33342583 }}</ref> A painted turtle can also sequester 44% of total body lactate in their shell.<ref>{{Cite journal |last=Jackson |first=D |date=1997 |title=Lactate accumulation in the shell of the turtle Chrysemys picta bellii during anoxia at 3°C and 10°C |journal=Journal of Experimental Biology |volume=200 |issue=17 |pages=2295–2300 |doi=10.1242/jeb.200.17.2295 |pmid=9320212 }}</ref> Despite the shell's large buffering contribution, it does not experience any significant decrease in mechanical properties under natural conditions.<ref name=":1">{{Cite journal |last1=Odegard |first1=D. T. |last2=Sonnenfelt |first2=M. A. |last3=Bledsoe |first3=J. G. |last4=Keenan |first4=S. W. |last5=Hill |first5=C. A. |last6=Warren |first6=D. E. |date=2018 |title=Changes in the material properties of the shell during simulated aquatic hibernation in the anoxia-tolerant painted turtle |journal=Journal of Experimental Biology |volume=221 |issue=Pt 18 |doi=10.1242/jeb.176990 |pmid=30065038 |s2cid=51890031 |doi-access=free }}</ref>

The duration of anoxia tolerance varies depending on the sub-species of painted turtle. The western painted turtle (''C.&nbsp;picta bellii'') can survive 170 days of anoxia, followed by the midland painted turtle (''C.&nbsp;picta marginata'') which can survive 150 days, and finally the eastern painted turtle (''C.&nbsp;picta picta''), which can survive 125 days.<ref name=":1" /><ref name=":3">{{Cite journal |last1=Reese |first1=S. A. |last2=Stewart |first2=E. R. |last3=Crocker |first3=C. E. |last4=Jackson |first4=D. C. |last5=Ultsch |first5=G. R. |date=2004 |title=Geographic variation of the physiological response to overwintering in the painted turtle (''Chrysemys picta'') |journal=Physiological and Biochemical Zoology |volume=77 |issue=4 |pages=619–630 |doi=10.1086/383514 |pmid=15449233 |s2cid=24651637 }}</ref><ref>{{Cite journal |last1=Reese |first1=S. A. |last2=Crocker |first2=C. E. |last3=Jackson |first3=D. C. |last4=Ultsch |first4=G. R. |date=2000 |title=The physiology of hibernation among painted turtles: the midland painted turtle (Chrysemys picta marginata) |journal=Respiration Physiology |volume=124 |issue=1 |pages=43–50 |doi=10.1016/S0034-5687(00)00188-2 |pmid=11084202 }}</ref><ref name=":4">{{Cite journal |last1=Ultsch |first1=G. R. |last2=Hanley |first2=R. W. |last3=Bauman |first3=T. R. |date=1985 |title=Responses to Anoxia during Simulated Hibernation in Northern and Southern Painted Turtles |journal=Ecology |volume=66 |issue=2 |pages=388–395 |doi=10.2307/1940388 |jstor=1940388 |bibcode=1985Ecol...66..388U }}</ref>  Differences in anoxia tolerance are partially attributed to the rate of lactate production and buffering capability in painted turtles.<ref name=":3" /> Furthermore, northern populations of painted turtles have a higher anoxia tolerance than southern populations.<ref name=":3" />

Other anoxia tolerant freshwater turtles include: the southern painted turtle (''Chrysemys dorsalis''), which can survive 75–86 days of anoxia, the snapping turtle ([[Common snapping turtle|Chelydra serpentina]]), which can survive 100 days under anoxia, and the map turtle ([[Northern map turtle|Graptemys geographica]]), which can survive 50 days of anoxia.<ref name=":3" /><ref name=":4" /><ref>{{Cite journal |last1=Reese |first1=S. A. |last2=Jackson |first2=D.C. |last3=Ultsch |first3=G. R. |date=2002 |title=The Physiology of Overwintering in a Turtle That Occupies Multiple Habitats, the Common Snapping Turtle (Chelydra serpentina) |journal=Physiological and Biochemical Zoology |volume=75 |issue=5 |pages=432–438 |doi=10.1086/342802 |pmid=12529844 |s2cid=32401168 }}</ref><ref>{{Cite journal |last1=Reese |first1=S. A. |last2=Crocker |first2=C. E. |last3=Carwile |first3=M. E. |last4=Jackson |first4=D. C. |last5=Ultsch |first5=G. R. |date=2001 |title=The physiology of hibernation in common map turtles (Graptemys geographica) |journal=Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology |volume=130 |issue=2 |pages=331–340 |doi=10.1016/S1095-6433(01)00398-1 |pmid=11544078 }}</ref> One reason for the difference in duration between more anoxia-tolerant species and less anoxia-tolerant species is the turtle's ability to buffer lactic acid accumulation during anoxia.<ref>{{Cite journal |last1=Jackson |first1=D. C. |last2=Taylor |first2=S. E. |last3=Asare |first3=V. S. |last4=Villarnovo |first4=D. |last5=Gall |first5=J. M. |last6=Reese |first6=S. A. |date=2007 |title=Comparative shell buffering properties correlate with anoxia tolerance in freshwater turtles |journal=American Journal of Physiology. Regulatory, Integrative and Comparative Physiology |volume=292 |issue=2 |pages=R1008–R1015 |doi=10.1152/ajpregu.00519.2006 |pmid=17008457 |s2cid=6911719 }}</ref>

Unlike adult painted turtles, hatchlings can survive only 40 days, but still exhibit high anoxia tolerance and freeze tolerance compared to other hatchling species (30 days for ''Chelydra serpentina'', and 15 days for ''Graptemys geographica'') due to cold winters.<ref name=":2">{{Cite journal |last1=Reese |first1=S. A. |last2=Ultsch |first2=G. R. |last3=Jackson |first3=D. C. |date=2004 |title=Lactate accumulation, glycogen depletion, and shell composition of hatchling turtles during simulated aquatic hibernation |journal=Journal of Experimental Biology |volume=207 |issue=17 |pages=3123 |doi=10.1242/jeb.207.17.3123 }}</ref><ref>{{Cite journal |last1=Dinkelacker |first1=S. A. |last2=Costanzo |first2=J. P. |last3=Lee |first3=R. E. |date=2005 |title=Anoxia tolerance and freeze tolerance in hatchling turtles |journal=Journal of Comparative Physiology B |volume=175 |issue=3 |pages=209–217 |doi=10.1007/s00360-005-0478-0 |pmid=15739066 |s2cid=12647870 }}</ref>{{Clear}}