Can turtles go underwater like a turtle

The turtle can stay under water for six months

Vienna - The Musk Tortoise (Sternotherus odoratus) has an extraordinary ability for reptiles: it can stay under water for a good six months without having to come up to breathe. Scientists working with Egon Heiss at the Department of Theoretical Biology at the University of Vienna have now investigated how the turtle achieves this: There are papillae in the turtle's mouth and throat - lobed surface structures with blood vessels that absorb the oxygen and carbon dioxide in the water submit. The research results were recently published in the journal The Anatomical Record released.

Enigmatic papillae

Like the proverbial fish in water, the musk turtle moves because it does not appear for up to six months. The starting point of the investigation was an analysis of the eating behavior: "We came across the lobed surface structures of the mouth and throat, which are particularly pronounced in the musk turtle," says Heiss. So far, the function of the papillae has been a mystery, because other turtle species that do not breathe under water also have surface-enlarging protrusions.

Since these large, branched papillae of the musk turtle are not related to food intake, the scientists researched their breathing. Until now it was assumed that gas exchange - absorbing oxygen, releasing carbon dioxide - takes place through the skin; Sea snakes, many amphibians and also softshell turtles "breathe" in this way. But the skin of the musk turtle is thick, horny and there are few vessels underneath. She cannot breathe with it.

"Gills" in the throat

The papillae are different: they are criss-crossed by numerous blood vessels. The researchers examined very thinly cut tissue that they obtained from the museum and of which they took digital images under the light microscope. A scanning electron microscope was also used, which provided remarkably high magnifications of the surface structures. Heiss explains: "The recordings show how present these papillae are. They are relatively large, branched and to be found in large numbers. And they are perfectly flushed, since the turtles regularly supply their throat with fresh water. Thus it is clear that these animals have developed something like gills. "

The musk turtle is unusual in many ways: with a size of 7.5 to 10 cm, it is one of the smallest species of turtle - giant turtles on the Galápagos Islands, on the other hand, reach a shell length of over one meter. Their appearance resembles - although a turtle - the tortoises; it is also able to scare off enemies with a strong smelling secretion. It is home to the fresh waters of North America, where it mainly eats snails. (red)