Continuous arterial PO2 profiles in unrestrained, undisturbed aquatic turtles during routine behaviors.
Mammals and birds maintain high arterial partial pressure of oxygen (PO2) values in order to preserve near-complete hemoglobin (Hb) oxygen (O2) saturation. In diving mammals and birds, arterial O2follows a primarily monotonic decline and then recovers quickly after dives. In laboratory studies of submerged freshwater turtles, arterial O2depletion typically follows a similar pattern. However, in these studies, turtles were disturbed, frequently tethered to external equipment and confined either to small tanks or breathing holes. Aquatic turtles can alter cardiac shunting patterns, which will affect arterial PO2values. Consequently, little is known about arterial O2regulation and use in undisturbed turtles. We conducted the first study to continuously measure arterial PO2using implanted microelectrodes and a backpack logger in undisturbed red-eared sliders during routine activities. Arterial PO2profiles during submergences varied dramatically, with no consistent patterns. Arterial PO2was also lower than previously reported during all activities, with values rarely above 50 mmHg (85% Hb saturation). There was no difference in mean PO2between five different activities: submerged resting, swimming, basking, resting at the surface and when a person was present. These results suggest significant cardiac shunting occurs during routine activities as well as submergences. However, the lack of relationship between PO2and any activity suggests that cardiac shunts are not regulated to maintain high arterial PO2values. These data support the idea that cardiac shunting is the passive by-product of regulation of vascular resistances by the autonomic nervous system.
Department of Ecology and Evolutionary Biology, School of Biological Science, University of California Irvine, Irvine, CA 92697, USA cassondrawilliams@sandiego.edu.|Center for Marine Biotechnology and Biomedicine, Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA 92093-0204, USA.
Cassondra L
0000-0002-3977-2900
CL
Williams
Department of Ecology and Evolutionary Biology, School of Biological Science, University of California Irvine, Irvine, CA 92697, USA.
James W
JW
Hicks
D000818:Animals; D059001:Aquatic Organisms / Q000502:physiology*; D001158:Arteries / Q000378:metabolism*; D001522:Behavior, Animal / Q000502:physiology*; D004566:Electrodes; D005260:Female; D010100:Oxygen / Q000378:metabolism*; D010313:Partial Pressure; D014426:Turtles / Q000502:physiology*
D010100:Oxygen
Arterial PO2; Blood oxygen depletion; Cardiac shunt; Diving; Trachemys scripta; Turtle