Most vertebrates have a elastic rib cage which allows the lungs to expand and contract through breathing. Numerous species of turtles have evolved distinct way of drawing air in their lungs. Turtles also have developed indirect methods for getting oxygen during times when they’re sealed from contact with the atmosphere, as when hibernating or staying underwater.
In turtles, the lungs lie just beneath the carapace and over the other internal organs. The top surface of the lungs attaches to the carapace itself, while the lower part is connected to the viscera (liver, heart, stomach, and intestinal tract) by a skin of connective tissue called diaphragmaticus. The viscera themselves can also be included within a membrane that attaches to the diaphragmaticus. Groups of muscles rhythmically change the amount of the abdominal cavity. 1 pair of muscles moves the viscera upward, pushing air from the lungs.
When turtles walk around, the motions of the forelimbs foster the compression and suction activities that encircle the lungs. A turtle can alter its lung volume by simply drawing its limbs , then extending them outward again: Turtles floating along with the water frequently can be seen moving their legs in and out, which helps them breathe. A turtle pulled back within its shell has no room in its lungs for air. At these and sometimes, turtles utilize various approaches to obtain oxygen.
Raising and lowering the hyoid apparatus causes a turtle’s neck to grow and drop, pulling in air. (Along with boosting ventilation, this air motion enables a turtle to better use its sense of smell.) To process oxygen rich water, a soft shell uses its hyoid apparatus to fill and empty its own throat in a procedure called buccopharyngeal breathing. When submerged, a soft shell typically pushes water out and in about 3 times a minute. Turtles that hibernate underwater also exchange gases through the throat lining, cycling the water within the throat cavity several times every minute. Many turtles practice this process of breathing, and a few turtles even take in oxygen through the cloaca.
Lots of the specifics of turtles breathing remain unidentified. What is clear however is that different sorts of turtles have evolved different procedures of fulfilling their oxygen requirements. Through evolution, they’ve gotten really good at obtaining this critical gas. As Ronald Orenstein notes in Turtles, Tortoises, and Terrapins: Survivors in Armor, turtles seem able to breathe”with the least amount of work regardless of what their situation.”