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Comparative Biochemistry and Physiology Part A 126 (2000) 223231 Respiratory responses to short term hypoxia in the snapping

Summary: Comparative Biochemistry and Physiology Part A 126 (2000) 223­231
Respiratory responses to short term hypoxia in the snapping
turtle, Chelydra serpentina
Sebastian Frische, Angela Fago, Jordi Altimiras *
Department of Zoophysiology, Danish Center for Respiratory Adaptation, Uni6ersity of Aarhus, DK-8000 A, rhus C, Denmark
Received 1 January 2000; received in revised form 22 March 2000; accepted 27 March 2000
Among vertebrates, turtles are able to tolerate exceptionally low oxygen tensions. We have investigated the
compensatory mechanisms that regulate respiration and blood oxygen transport in snapping turtles during short
exposure to hypoxia. Snapping turtles started to hyperventilate when oxygen levels dropped below 10% O2. Total
ventilation increased 1.75-fold, essentially related to an increase in respiration frequency. During normoxia, respiration
occurred in bouts of four to five breaths, whereas at 5% O2, the ventilation pattern was more regular with breathing
bouts consisting of a single breath. The increase in the heart rate between breaths during hypoxia suggests that a high
pulmonary blood flow may be maintained during non-ventilatory periods to improve arterial blood oxygenation. After
4 days of hypoxia at 5% O2, hematocrit, hemoglobin concentration and multiplicity and intraerythrocytic organic
phosphate concentration remained unaltered. Accordingly, oxygen binding curves at constant PCO2
showed no changes
in oxygen affinity and cooperativity. However, blood pH increased significantly from 7.5090.05 under normoxia to
7.7290.03 under hypoxia. The respiratory alkalosis will produce a pronounced in vivo left-shift of the blood oxygen
dissociation curve due to the large Bohr effect and this is shown to be critical for arterial oxygen saturation. © 2000


Source: Altimiras, Jordi - Department of Biology, Linköpings Universitet


Collections: Environmental Sciences and Ecology