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If there’s something you generally think is a rule of nature, chances are there’s an animal breaking it. Octopus have nine brains to control their eight legs and three hearts to effectively circulate to their limbs. star-nose moles are in fact blind, but the bizarre tentacles protruding from their noses can create a sophisticated map of the world around them by touch alone. And a jelly in the cheeks of sharks makes them incredibly sensitive to the electric fields of other creatures. But not every bizarre animal fact is true, and the claim that turtles being able to breathe from their butts seems to be one of the most ridiculous. But it’s true, at least up to a point. The process is cloacal breathing, and it makes for one of the more fascinating examples of natural selection at work in nature.
What is a Cloaca?
Technically, turtles don’t even have butts – and the cloaca serves a similar function to their bodies, although it has more uses. As the end point of both the urinary tract and the digestive tract, it drains all body waste. The cloaca is also a reproductive opening for females, and males of some species use it instead of a phallic sex organ. The concept of the cloaca may seem strange to humans, but it is more the rule than the exception in the animal kingdom. reptiles, birds, and amphibians all manifest cloaca rather than different urinary and digestive systems – like many species of fish.
Most mammals have evolved waste systems more advanced than the cloaca, although there are rare exceptions, such as the golden one wart. And while the scientific community doesn’t agree on exactly how these separate waste systems evolved, we can still see their presence in human embryo development and traces where it once existed in marsupials.
How does cloacal breathing work?
In the same way that the cloaca isn’t technically a butt, what turtles do with it isn’t technically breathing. Despite this, it provides the same basic resources that all animals need: oxygen. Essentially, it’s just another way the cloaca serves as an all-purpose waste disposal system. By tightening their cloacal muscles, they can inhale water in much the same way that our breath inhales air. The water is then taken to a pair of organs known as bursae, which act similarly to lungs — the unique tissues taking the oxygen from the water and expelling the unwanted hydrogen. The oxygen then filters through the tissue into the bloodstream where it is transported to the rest of the body. The landscape may seem unfamiliar, but the path is still the same.
Why do turtles use cloacal breathing?
The simple answer is that turtles need to breathe underwater and cloacal bursae development has proven to be the most effective solution aside from growing gills – but not all turtles are even capable of cloacal breathing. Its presence with reptiles tells us a lot about their habits and about their complicated relationship with breathing. The average turtle species will spend about 60% of their time in the water and the rest on land, and most of them face the same dilemma as dolphins in the sense that they have to surface to breathe. By surfacing, they can become easy prey for birds of prey such as gulls and seagulls herons as well as aquatic predators prowling the surface like crocodiles and sharks.
When breathing air, a turtle’s lungs are functionally a little different from a human’s, although the fact that they carry their ribs on the outside requires them to have special muscles to breathe. A breathing process called buccopharyngeal pumping allows turtles to filter the oxygen from the water using specialized membranes built into their mouths. But turtles have an advantage over aquatic mammals such as: whales and dolphins simply because they are reptiles. Without the need to regulate body temperature, oxygen is needed in much lower volumes. sea turtles can hold their breath for up to two hours when active and three to four times as much when they sleep.
In any case, cloacal breathing is a supplement rather than a replacement for the more traditional breathing. Every turtle will eventually have to surface to get some air, but cloacal breathing can help them extend their time underwater for a significant amount of time. This is most useful during the colder months. When rivers and lakes freeze, many turtles will simply retreat underwater into a state of rest – equivalent to the hibernation that bears, squirrels, and other mammals run through.
The colder temperatures cause the turtle’s metabolism and energy needs to plummet, and that allows some species to remain submerged for months, depending solely or mainly on their cloaca for oxygen. But cloacal breathing does not seem to have developed exclusively for this purpose. In less extreme climates and seasons, turtles can rely on this breathing method as a sort of reserve tank, allowing them to avoid surface predators or forage in deeper waters.
Which turtles are capable of cloacal breathing?
Regardless of how it’s used, this unique form of breathing has been useful enough to develop into a number of different varieties. Here are some of the more famous ones:
- the oriental painted turtle is one of the most successful species of turtles in North America, with a habitat extending from Canadaeast coast all the way to the state Georgia. They rely on cloacal breathing to hibernate and even taking calcium from their shell as a way to offset the toxicity of the low oxygen levels in their blood.
- the white throat biting turtle is a Australian species that is also one of the largest turtles in the world. This Queensland turtle is endangered but can re
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in submerged in fresh water for up to three hours at a time. It is believed that nearly half of this underwater turtle’s oxygen comes from its cloacal bursae. - The Fitzroy river turtle is also found in Queensland, albeit in the much smaller habitat of the river of the same name and its tributaries. These turtles spend almost their entire lives in the water and up to 70% of their oxygen can be obtained from cloacal respiration.
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