

Courtesy Dawson via Wikimedia CommonsThe common musk turtle (Sternotherus odoratus) has a strange way of extracting oxygen from its surroundings – it breathes through its tongue. It’s certainly not the strangest way of taking a breath (as you’ll discover if you read further), but it is one scientists weren’t expecting to find.

Turtles have been around since the Late Triassic some 225 million years ago when they first appeared in the fossil record. A lot of the breed’s success has to do with its rigid protective shell (carapace), and being able to protect itself under it. Another is its ability to stay underwater for long periods of time without coming up for air and exposing itself to surface predators. But because the shell develops out of a turtle’s ribcage, limitations are imposed on its ability to breathe in what we consider the “normal way”. So turtles have come up with all kinds of interesting adaptations for extracting oxygen from their surroundings. Some, like the Painted turtle (Chrysemys picta) can stay submerged for 4 to 6 months while hibernating. It does this by slowing down its metabolism which subsequently reduces the production of lactic acid in its system. Others can breathe through their skin, others through their rear ends (okay, a major “ewwww” factor here – but of course who are we to judge?). The musk turtle’s ability to breathe through its tongue adds just another bizarre method to the family’s repertoire.

The musk turtle (aka stinkpot turtle – a great name by the way) is so named because of the disagreeable odor it can produce to fend off predators. It spends most of its life underwater, and can live for months at a time submerged without coming up for air. The species doesn’t breath through its skin as some other turtles do. Nor does the stinkpot turtle breathe through its butt like Australia’s Rheodytes leukops does. R. leukops possesses specialized bursae, large sacs in its rear orifice (cloaca) that can draw water in and out to get precious oxygen to its blood in that manner. The cloacal bursae are used to get nearly 70 percent of it oxygen. How bizarre is that?

Anyway, back to the stinkpot turtle. So now scientists have discovered S. odoratus’s breathing secrets. It all has to do with the cells called papillae that line its tiny tongue. As water flows past, the papillae are able to absorb oxygen. (We humans also have papillae on our tongues but they don’t extract oxygen from the atmosphere).

Egon Heiss, a PhD candidate at the University of Vienna in Austria, along with his colleagues, discovered the stinkpot’s secret while studying juveniles of the species. While an adult italicizedSternotherus odoratus tends to spend most of its life underwater, its young offspring do occasionally venture onto land in search of food. The researchers noticed the reptile youngsters wouldn’t eat their food on land but instead dragged it back into the water. This led the researchers to the creature’s tongue and its unique function. The team’s research appears in the journal The Anatomical Record.

LINKS

BBC story

More turtle facts

Turtles of the World site