The effects of environmental temperature, hypoxia, and hypercapnia on the breathing pattern of saltwater crocodiles (Crocodylus porosus).

This study aimed to describe the effects of change in environmental temperature, hypoxia, and hypercapnia on the breathing pattern of Crocodylus porosus. Increased environmental temperature, hypoxia, and hypercapnia each caused an increase in minute ventilation and changes in breathing pattern. Breathing frequency increased and the duration of the nonventilatory period decreased in response to all three conditions. Under hypercapnia tidal volume also increased, with no change in rate of inspiration. The number of breaths per breathing burst decreased with increased temperature but remained unaltered under hypoxia. Hypercapnia reduced the number of breaths per burst at 20 degrees C, but the number did not decrease further at 30 degrees C. The results support the idea that the responses to increased temperature, hypoxia, and hypercapnia are under separate control but that some effects of hypercapnia and temperature may involve a common regulatory pathway.