Turtles, despite their aquatic lifestyles, do not possess gills like fish do. They are reptiles, and like all reptiles, they breathe air using lungs. However, they have developed remarkable adaptations that allow many species to remain submerged for extended periods, sometimes leading to confusion about their respiratory mechanisms.
The Primary Answer: Lungs
Turtles primarily breathe using their lungs, which function similarly to those of other terrestrial vertebrates. Air enters through their nostrils and moves down the trachea into the lungs, where oxygen is absorbed into the bloodstream. Their lungs are located beneath the carapace, the upper part of their shell.
The rigid shell of a turtle presents a unique challenge for lung ventilation, as it prevents the rib cage from expanding and contracting in the same way human ribs do. To overcome this, turtles use specialized muscles attached to their pelvic and shoulder girdles and to the plastron (the lower shell) to facilitate inhalation and exhalation. Some turtles also use movements of their limbs in and out of the shell to alter pressure and aid in lung ventilation.
Beyond Lungs: Specialized Breathing
Beyond their primary lung respiration, many aquatic turtle species employ supplementary methods to absorb oxygen when submerged. One adaptation is cloacal respiration, often called “butt breathing.” In some species, like the Eastern snapping turtle and Fitzroy River turtle, the cloaca contains highly vascularized sacs (bursae) that pump water, allowing oxygen diffusion into the bloodstream.
Another method is cutaneous respiration, where oxygen is absorbed directly through the skin, especially in areas with rich blood supply like the neck, tail, or limb pits. This “skin breathing” contributes to oxygen uptake, particularly in smaller turtles. Additionally, some turtles engage in buccal pumping, rhythmically moving the floor of their mouth to circulate water over vascularized membranes in their throat, facilitating oxygen absorption. These alternative methods are less efficient than lungs but become important in low-oxygen environments or during prolonged dives.
Underwater Survival Without Gills
Turtles survive prolonged periods underwater without gills by combining specialized breathing methods with physiological adaptations. Their ability to lower their metabolic rate is important, especially in cold water or during brumation (a reptile’s winter dormancy). A reduced metabolism means they require less oxygen to sustain bodily functions.
When oxygen becomes scarce or depleted, turtles can switch to anaerobic respiration, a process that generates energy without oxygen. While this allows survival in oxygen-poor conditions, it leads to lactic acid buildup, limiting how long they can maintain this state. Some species, like painted turtles, mobilize calcium from their shells to neutralize this acid. Their capacity to store oxygen in blood and muscles, combined with a slowed heart rate during dives, enhances underwater endurance. This allows some species to remain submerged for hours, or even months during brumation.