Metabolic and ventilatory responses to hypoxia in two altitudinal populations of the toad, Bufo bankorensis

Effects of hypoxia on resting oxygen consumption ((M) over dot (O2)), lung ventilation, and heart rate at different ambient P-O2 were compared between lowland and high altitude populations of the toad, Bufo bankorensis. Resti ng (M) over dot (O2) decreased significantly in mild hypoxia (P-O2 = 120 mm Hg) at 10 degrees C and in moderate hypoxia (P-O2 = 80 mm Hg) at 25 degree s C in both altitudinal populations; however, resting (M) over dot (O2) did not differ significantly between the two populations. Numbers of lung vent ilation periods (VP) and total inspired volume (V-L) did not change with P- O2 at 10 degrees C, but did increase at moderate and severe hypoxia (40 mm Hg), respectively, at 25 degrees C. Resting heart rates did not change duri ng hypoxia and did not differ between altitude populations. The results sug gest (1) the effect of P-O2 change on (M) over dot (O2) should be considere d in future studies involving transfer of anurans to a different altitude; and (2) the metabolic and ventilatory physiology in B. bankorensis does not compensate for the low temperature and P-O2 at high altitude. (C) 1999 Pub lished by Elsevier Science Inc. All rights reserved.