Although many turtles spend large amounts of their lives underwater, all turtles and tortoises breathe air,
and must surface at regular intervals to refill their lungs. They can also spend much of their lives on dry
land. Aquatic respiration in Australian freshwater turtles is currently being studied. Some species have large
cloacal cavities that are lined with many finger-like projections. These projections, called papillae, have
a rich blood supply, and increase the surface area of the cloaca. The turtles can take up dissolved oxygen
from the water using these papillae, in much the same way that fish use gills to respire.
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