Acid-base balance and temperature in a predominantly skin-breathing salamander, cryptobranchus alleganiensis

Blood gases and pH and plasma [Na +], [K +], [Cl −] and [lactate] were measured on arterial blood of the large predominantly skin-breathing salamander, the hellbender (Cryptobranchus alleganiensis), at 5, 15 and 25°C, both with and without access to air. Access to air had no effect on any of the acid-base variables, but temperature had significant effects on both pH and P CO 2 . Blood pH decreased with temperature by about 0.016 unit/°C both in vivo and in vitro (over the range studied) which is similar to the change previously observed on other ectotherms. Blood P CO 2 rose significantly with temperature while plasma [HCO 3 −] rose slightly but insignificantly. Other ions were unaffected by temperature. This is the first demonstration that the characteristic ectothermic acid-base response to temperature occurs in a vertebrate respiring exclusively through its skin. We suggest that the response in this animal is essentially passive and uncontrolled and is due to: 1. (1) the proportional effects of temperature upon metabolic CO 2 production and blood P CO 2 , and 2. (2) the temperature-independent CO 2 conductance of the skin.