Allometric scaling of lung volume and its consequences for marine turtle diving performance

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Marine turtle lungs have multiple functions including respiration, oxygen storage and buoyancy regulation, so lung size is an important indicator of dive performance. We determined maximum lung volumes ( V L) for 30 individuals from three species ( Caretta caretta n = 13; Eretmochelys imbricata n = 12; Natator depressus n = 5) across a range of body masses ( M b): 0.9 to 46 kg. V L was 114 ml kg −1 and increased with M b with a scaling factor of 0.92. Based on these values for V L we demonstrated that diving capacities (assessed via aerobic dive limits) of marine turtles were potentially over-estimated when the V L-body mass effect was not considered (by 10 to 20% for 5 to 25 kg turtles and by > 20% for turtles ≥ 25 kg). While aerobic dive limits scale with an exponent of 0.6, an analysis of average dive durations in free-ranging chelonian marine turtles revealed that dive duration increases with a mass exponent of 0.51, although there was considerable scatter around the regression line. While this highlights the need to determine more parameters that affect the duration-body mass relationship, our results provide a reference point for calculating oxygen storage capacities and air volumes available for buoyancy control.