Recently, I asked a boat-load of youngsters what they could tell me about sea turtles. Among the answers, was ‘they can breathe through their butts’. And interestingly enough, as much as I tried to dislodge that visual from the 9-year-old’s mind from which it sprang, I couldn’t. I couldn’t because his best friend is possessed by sea turtles and that friend, like many nine year-old kids, has unfettered access to the nearly infinite sea of information online. On the Internet his friend had learned that sea turtles could breathe through their butts, and this kid was sticking with his trusted, best friend, not ole Doc Bruce.
So, online we will go. Firstly, turtles don’t have ‘butts’; their anatomy is different than ours. Reptiles and birds (some fish and even a few mammals) have a single opening through which the digestive, excretory and reproductive systems all open, the cloaca. The term cloaca is derived from the Latin cloāca meaning sewer, which was derived from cluō meaning to cleanse.
Secondly, the word breathing is typically used to describe the process through which animals bring air in to their bodies; extracting oxygen from that air, adding carobon dioxide to it and release it back to the external world. A more general term used to describe this gas exchange among animals is respiration. Respiration can occur both in air and in water – where many animals exchange the gasses oxygen and carbon dioxide from water.
Thirdly, there are two main groups of living turtles, which are fairly distinct from one-another. A major difference between the two is how they retract their heads into their shells. Most turtles, including sea turtles belong to the cryptodire group; the second, and much smaller group, the pleurodires are limited in geography to South America, Australia and Africa.
Some of the pleurodires have a pair of enlarged, blind pouches arising from the internal walls of the cloaca called bursae. The cloacal bursae in some pleurodire species are highly vascularized and have been shown to carry out a respiratory function. Some fresh water turtles carry out cloacal respiration, as do some dragonfly larvae and sea cucumbers.
From some relatively small fresh-water turtles carrying out cloacal respiration to sea turtles breathing through their butts. Like so many legends, there is an interesting nugget of information at its core. However, living things are extremely complex; there are always exceptions to rules and just about every weird thing imaginable has been done along the pathway of evolutionary history. Problems arise when we apply what we think we know about one living creature to its relatives.
So for all you sea turtle lovers – of any age, here’s the straight-up truth – to the best of our current knowledge, sea turtles don’t breathe through their butts, If they did, we would call it cloacal respiration and very proudly add that to one of the many reasons we so love those leviathans of the sea.
And, like everything else in life, a good education takes a lot of work. We are lulled by the comfort that perhaps a single google search will rapidly reveal a Holy Grail. At least in biology, it rarely does.