Hemoglobin function in a skin-breathing aquatic salamander, Desmognathus quadramaculatus

Adult black-bellied salamanders (Desmognathus quadramaculatus) were maintained in humidified gas at 12 degrees C. Hypoxic salamanders were exposed to 8.1-9.6% O2 for 10-11 days; normoxic animals were maintained in air (20.9% O2). Hypoxia acclimation had no effect on blood O2 affinity, O2 equilibrium curve shape or CO2 Bohr effect. At pH 7.7, P50 values for hypoxic and normoxic salamanders were 28.2 +/- 0.4 and 28.6 +/- 0.8 Torr, respectively. Hill plots were curvilinear for both treatments; Hill's n increased from values of 2.1-2.2 below 40% saturation (S) to 2.6 above 50% S. CO2 Bohr slopes (delta log P50/delta pH) were -0.19 +/- 0.01 and -0.23 +/- 0.02 for hypoxic and normoxic animals, respectively. Resting MO2 for a separate group of normoxic salamanders fell into two categories; low MO2 (1.46 +/- 0.16 mumol.g-1.h-1) and high MO2 (3.51 +/- 0.52) animals. Exposures to 5 and 25% CO had no effect on MO2 of low metabolism Desmognathus, but reduced MO2 of high metabolism animals to levels similar to the low MO2 group. Hb-O2 binding results suggest that D. quadramaculatus blood is ideally suited for respiratory O2 exchange during normoxic activity. While submerged and inactive, hypoxic boundary layers surround the skin-breather. Contributions of Hb during hypoxic inactivity may be to augment O2 content and increase blood buffering capacity.