Heat production during diving in the fresh water turtle, Pseudemys scripta

Heat production was measured calorimetrically in the turtle, Pseudemys scripta elegans , (a) while submerged and (b) while partially submerged and breathing various gas mixtures. Submersion resulted in a profound reduction of heat production (80%). This reduction was not merely a response to the dive per se , but depended on the oxygen concentration available to the turtle prior to the onset of the dive. Heat production while breathing gas mixtures with different O 2 concentrations was unchanged down to 5% O 2 . At 3% O 2 , heat production was 50% of normal, and at 100% N 2 , it was 20% of normal. Uptake of dissolved O 2 from water was found to be 6% of the O 2 uptake from air by these turtles. These results suggest that following diving, there is a profound reduction in metabolic rate, but not until the O 2 stores are depleted. This low rate is primarily anaerobic and only a very low oxidative metabolism can be supported by O 2 extracted from the water.