Seasonal Oxygen-Metabolism and Cutaneous Osmoregulation in California Newt, Taricha-Torosa

While breathing air at rest, aquatic Taricha torosa consumed 0.054 cm302 g-1 h-1, which represent oxygen metabolism twice that of the terrestrial phase. There was no significant difference in the rate of oxygen consumption between phases upon sub-mergence. Aquatic newts accumulated a significantly higher lactate debt than the terrestrial phase while underwater. Aquatic newts had a higher emerged heart rate and exhibited a significantly greater bradycardial response after 40 min of dive. Although initiation of the response was relatively slow in both phases, lowest heart rates were realized after 60-120 min. The reduced oxygen uptake and increased blood lactate levels during a dive by aquatic newts suggest that skin permeability may be a limiting factor for oxygen uptake. Data from this study do not indicate cutaneous changes to have respiratory consequence. Aquatic T. torosa skin exhibited significantly lower in vitro rates of water transfer in an osmotic gradient of 210 mOsm/liter and a significantly greater rate of sodium transport when compared to the terrestrial phase. The results of these experiments imply an osmoregulatory function for seasonal morphological skin changes displayed by T. torosa.