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

Adult black-bellied salamanders ( Desmognathus quadramaculatus) were maintained in humidified gas at 12 °C. Hypoxic salamanders were exposed to 8.1–9.6% O 2 for 10–11 days; normaoxic animals were maintained in air (20.9% O 2). Hypoxia acclimation had no effect on blood O 2 affinity, O 2 equilibrium curve shape or CO 2 Bohr effect. At pH 7.7, P 50 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. CO 2 Bohr slopes ( Δlog P 50 Δ pH ) were −0.19 ± 0.01 and −0.23 ± 0.02 for hypoxic and normoxic animals, respectively. Resting M O 2 for a separate group of normoxic salamanders fell into two categories; low Ṁ O 2 (1.46 ± 0.16 μmol·g −1·h −1) and high Ṁ O 2 (3.51 ± 0.52) animals. Exposures to 5 and 25% CO had no effect on Ṁ O 2 of low metabolism Desmognathus, but reduced Ṁ O 2 of high metabolism animals to levels similar to the low Ṁ O 2 group. Hb–O 2 binding results suggest that D. quadramaculatus blood is ideally suited for respiratory O 2 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 O 2 content and increase blood buffering capacity.