Turtles, as reptiles, possess lungs for respiration. This means that most turtle species, despite their ability to spend significant time underwater, must regularly surface to breathe air. Their existence relies on atmospheric oxygen for biological functions.
Respiratory System Basics
All turtles depend on lungs for gas exchange, making them obligate air-breathers. Their respiratory system extracts oxygen from the air and expels carbon dioxide. Oxygen is essential for cellular respiration, which generates energy for all bodily functions. Without a consistent supply of oxygen, a turtle’s metabolic processes cannot function. The lungs, located beneath their rigid carapace, serve as the primary organs for gas exchange.
The Act of Breathing
When a turtle needs to breathe, it typically surfaces, often exposing only its nostrils. Unlike mammals, turtles cannot expand and contract their rib cage to ventilate their lungs because their ribs are fused to their shell. Instead, they rely on a unique muscular system to change the volume within their body cavity. Specialized abdominal muscles, such as the transversus abdominis and obliquus abdominis, contract and relax to push and pull internal organs, compressing and expanding the lungs. Movements of their pectoral (shoulder) and pelvic (hip) girdles, and even their limbs, also contribute to pumping air in and out.
Specialized Breathing Methods
Some aquatic turtles possess remarkable adaptations that allow them to extend their time underwater by supplementing their oxygen intake.
Cloacal Respiration
This method, sometimes informally called “butt breathing,” involves absorbing oxygen from water through specialized, richly vascularized sacs called bursae, located within their cloaca. Species like the Fitzroy River turtle and Mary River turtle are notable for their efficiency, with the Fitzroy River turtle capable of deriving a significant portion of its oxygen this way, allowing for extended submersions.
Pharyngeal and Cutaneous Respiration
Pharyngeal breathing involves some turtles, particularly softshell turtles, absorbing oxygen through the vascularized lining of their throat (pharynx). This involves pumping water over small, finger-like projections called villiform processes, which facilitate gas exchange. Cutaneous respiration, or breathing through the skin, also occurs to a lesser extent, especially in smaller or juvenile turtles, or during periods of dormancy.
Factors Influencing Submersion Time
Several factors influence how long a turtle can remain submerged. Water temperature significantly impacts metabolic rate; in colder water, a turtle’s metabolism slows, reducing its oxygen demand and allowing for longer dive times. Activity level is another determinant; a resting turtle can hold its breath for much longer than one actively swimming or foraging, sometimes for several hours. Stress, however, can rapidly deplete oxygen reserves, potentially leading to drowning. These specialized methods and physiological adjustments enable turtles to thrive in diverse aquatic environments.