If you have seen a turtle in real life or kept one as a pet, you might be wondering how the creatures get a fresh supply of oxygen, especially now that there are several theories about how they do it. Like all animals, turtles breathe in oxygen and release carbon dioxide into the atmosphere. And they do this through the lungs, which are their primary respiratory organ.
However, the turtle’s respiratory system is a little different from that of mammals since it’s modified to suit a range of various bizarre morphological features. Although aquatic turtles need to come to the water surface to gulp oxygen, their bodies have sophisticated adaptations that allow them to stay underwater for extended periods.
They also boast other extraordinary organs that enable them to continue absorbing small amounts of oxygen even when they’re not breathing through the lungs.
If you want to understand more about turtles’ respiration, we’ll cover everything from how they breathe, how they survive underwater, and they cope with the cold winter weather.
How Do Turtles Breath?
Of course, turtles use their lungs as the primary source of their oxygen. However, they still leverage other parts to get adequate oxygen supply underwater. These calm and docile shell-carrying creatures can get oxygen supply in three ways, including:
- Breathing through the lungs
- Absorption through mouths and throats
- Breathing through the butts
Breathing through the Lungs
Lungs are the turtle’s main respiratory organ and are often used when the creatures are above the water surface. Essentially, turtles need to come to the surface to gulp some air. However, one unique element about the turtle lungs is that they help these creatures respire and act as a store to reserve oxygen the turtles use when they dive in the water.
Air gets in through nose-like structures above the turtle’s mouth known as nares. The air moves down the glottis and then into the trachea, made of multiple rings of cartilage. The turtle’s trachea is long and flexible. This allows the turtle to extend and tuck its head into the shell without interfering with air supply into the lungs.
The trachea extends up to the heart and divides into two bronchi that deliver air to each lung. Once the air reaches the lungs, it is filtered, and oxygen is absorbed into the bloodstream.
Aquatic turtles feature subdivided, multicameral lungs with highly reinforced and wide airways. The lungs also boast uniformly distributed parenchyma lined with smooth muscles and extensively connected tissues. Due to these profound features, sea turtles have one of the highest respiratory flows.
With a vital capacity (VC) as large as the total lung capacity, sea turtles can fill nearly the whole lung volume with a single breath. It’s this capability that allows turtles to take one deep breath and dive into the water and stay submerged for hours.
Air Absorption through Mouth/Throat System
Turtles are often seen moving their throats with their mouths are wide open. Although there is plenty of misleading information claiming that turtles do this to pump air into the lungs, this is further from the truth. According to research, the cheek (buccal) pumping and throat (gular) pumping don’t correlate in any way to lung inflation.
Researches claim that turtle species pump their throats and mouths for smelling or olfaction. They can detect the smell of prey or predator through the pumping process.
However, they also claim that the buccal and gular pumping help these creatures absorb oxygen. Essentially some aquatic turtle species absorb oxygen across the surfaces inside their throat and mouth. Since these surfaces are moist, they diffuse oxygen, which is then transported to the turtle’s internal organs.
So, the next time you see turtles swimming with their mouths wide open, just know they are trying to catch some smell or maybe diffuse some oxygen from the water.
Cloacal Respiration
You must have heard that turtles can breathe through their butts. Although this might seem unbelievable, it is actually true, and the process is known as cloacal respiration.
Turtles boast a unique orifice known as the cloaca at the base of their tail. Besides performing functions like reproduction, excretion, and urination, the cloaca also helps turtles absorb oxygen from the water.
When turtles are submerged in water, the cloaca allows water into specialized pouches known as cloacal bursae. The pockets are lined up with small, finger-like projections that increase the surface area for absorption. Additionally, they boast extensive capillaries that help absorb oxygen from the water into the bloodstream. The turtle sucks oxygen out of the water and then expels it.
Because of how the cloaca operates, oxygen absorption through the cloacal respiration is less exhausting. The bad news is that the oxygen absorbed through this process can only suffice for a short period during normal conditions. However, when sea turtles are hibernating during winter, cloaca breathing can sustain a turtle for 3 to 4 months.
Do Turtles Have a Diaphragm?
Although both human beings and turtles have lungs, turtles lack a diaphragm to suck in oxygen and release carbon dioxide. One thing about turtles is that lung ventilation is a significant problem since all turtle’s internal organs are encased in the rigid shell. The shell’s rigidity means that the creature’s ribs can’t expand or contract and can’t be used as an aspiration pump.
However, turtles boast unique muscles within the inner walls of their shells, which contract and relax to force air in and out of the lungs. The fact that turtle ribs are conjoined with other bones to form the shell negates the usual movements that aid in lung ventilation in other animals. Instead of a diaphragm, turtles come with reinforced abdominal-muscle apparatus that helps suck in air and push out carbon dioxide.
Due to their unique body structure, turtles can’t experience normal ventilation like other amniotes. With the ribs firmly bound to the shell, another mechanism to encourage lung ventilation was imperative. This is the primary reason have why turtles have a specially designed apparatus that boasts two antagonistic abdominal muscles that facilitate breathing.
Can Turtles Hold Their Breath?
A single breath of fresh air is enough to last turtles underwater for several hours. Essentially, sea turtles can hold their breath for hours based on their activity level. Freshwater turtles can hold their breath for 5 hours when they are sleeping.
When hibernating, turtles can stay underwater without breathing for up to 7 hours. Since there’s minimal movement, these creatures can conserve a lot of oxygen. During routine activities such as swimming or scavenging for food, turtles can hold their breath for 45 minutes. Nevertheless, these shell-carrying creatures only dive for 4 to 6 minutes and resurface to take a breather for a few seconds.
However, when a turtle is stressed, sick, or entangled in aquatic plants or fishing nets, it can quickly use up its oxygen reserve and drown. This brings us to our next question.
Can Terrestrial Turtles Hold their Breath?
Since terrestrial turtles don’t have any reason to hold their breath, nobody knows whether they can stay without breathing or not. They can survive on land by hiding under rocks during the cold season, but they don’t need to hold breath since they’re not surrounded by anything.
Can Turtles Drown?
Although turtles can hold their breath, they can’t breathe underwater. Therefore, turtles will drown if they don’t get adequate oxygen supply like any other creature with lungs. However, this isn’t something that often happens since turtles are adapted to living in aquatic habitats.
Even though it is unlikely, several cases of turtles drowning have been documented, all associated with the creatures being caught up underwater. Most of the reported incidences include turtles entangled in fishnets and ghost gears.
When turtles get trapped, they get stressed and deplete their oxygen reserves in minutes. Drowning symptoms include lack of reflexes, comatose, water in the lungs, and alteration of various organs when inspected using radiographs.
Under undue stress, turtles may use up all the oxygen and trigger anaerobic respiration, leading to lactic acid build-up. If this type of respiration goes on for hours, it can become toxic and lead to a quick death if the turtle can’t swim to the surface to catch a breath.
Turtles that have drowned may not necessarily die inside the water. When they come out of the water when unconscious, they usually have a 50% chance of survival. To avoid any turtle drowning, pet turtle owners should ensure that the turtle tank doesn’t have any foreign materials, such as nets or ropy plants, which may trap turtles, especially the juveniles.
How Turtles Breath When in Hibernation?
Being cold-blooded, turtles’ activity level inherently depends on the external temperature. The docile creatures are always active in the warmer months, but their rate of activity and metabolism decreases when temperatures plummet. When the temperature drops to unbearable levels during the cold season, turtles slow down their metabolism by hibernating.
When ice and snow start to cover lakes and ponds, most turtles descend into the bottom of the water and hibernate. Unlike humans that leverage their metabolism to maintain steady body temperature, turtles’ internal temperature adjusts based on the temperature in the environment.
Ice-covered sea or pond brings two problems to turtles. First, they make it impossible for turtles to get to the surface and take a breather. Secondly, they allow less oxygen to diffuse into the water, making it hard for aquatic animals to get adequate oxygen. They become hypoxic or anoxic during winter, making it daunting for marine animals to survive.
Luckily, some turtle species can survive in such conditions. Painted and snapping turtles usually switch to metabolism that doesn’t need much oxygen. At the same time, the ability to withstand hypoxic or anoxic conditions may be pretty impressive but can be dangerous or even lethal if it goes on for too long. Snapping and painted turtles can stay submerged in ice-cold water for over 100 days.
Painted turtles are considered the kings of anoxia tolerance since they collect calcium from the cells to neutralize the lactic acid formed during the long period of oxygen inefficiency. When turtles get out of hibernation in the spring, they look more than a big muscle cramp due to lactic acid accumulation. They crave basking in the sunshine to kick start their metabolism and eliminate lactic acid build-up.
What Is Acidosis?
In the last section, we mentioned that inadequate oxygen induces anaerobic respiration, leading to lactic acid formation. When too much of this acid accumulates in the body, it can result in a dangerous condition known as acidosis. If the condition is not reversed, it can lead to death.
When turtles accumulate high lactic acid levels, they exploit the abundant reserves in their mineralized shells to bring the acidity to optimal levels. Essentially, turtle shells come with calcium and magnesium carbonates, which are released to lower the high lactate in the blood.
These compounds react with lactic acid to prevent the turtle from getting fatal acidosis. Together with a suppressed metabolism, the shell buffers allow turtle species to hibernate for months at Celsius.
Conclusion
No matter how you perceive turtles, they are some of the world’s most amazing survivors. Despite having a rigid shell that incorporates the ribs, they still have potent lungs that allow the free flow of air. They boast reinforced abdominal-muscle apparatus on the inner shell, which relax and contract to allow oxygen in and carbon dioxide out of the lungs.
Conversely, these docile and slow-walking creatures can absorb oxygen through their mouth and throat. They also breathe through an orifice at the base of the tail known as the cloaca. It’s this cloacal respiration that enables these reptiles to survive even the coldest months during winter.
Although being able to withstand extreme conditions is one of the turtle’s most fancied attributes, it comes at a cost. When in hibernation, turtles have to tread carefully to ensure they don’t use up all the oxygen and suffer acidosis, which can be fatal. So, if you were wondering how turtles get their oxygen supply and how they cope with the cold climate, now you have the answers.
