qWho hasn’t dreamed of enjoying a sixth sense? A unique gift that would allow you to see in the dark or ultraviolet, hear ultrasound or infrasound, echolocate like a bat or a dolphin. Or something even more unlikely, that neither you nor I could imagine… This sounds a bit like what an American team has just discovered in the tokay gecko. In an article published on October 4 in the magazine Current biologyCatherine Carr and Dawei Han, from the University of Maryland, have just shown that this reptile could “hear” non-sound vibrations thanks to vesicles in the inner ear: the saccules.
These small cavities are not unknown to us. Housed in the inner ear, they help guarantee our balance. For us, but also for all other land animals. In fish and some species of amphibians, on the other hand, these same saccules allow those interested to perceive sounds that circulate through the water or land. Could the same happen with other groups, such as reptiles?
To answer this question, the two American researchers looked at geckos. And not just any ones: the tokays. Like all their cousins, they are characterized by their nocturnal lifestyle and the sticky pads that cover their paws and allow them to climb any vertical surface, including glass. But, in addition to their respectable size (20 centimeters without tail) and a somewhat aggressive character, tokays are famous for their singing. In other words, and unlike many other reptiles, they hear. Sounds, of course, caused by the air pressure in your ears. But also very low frequency vibrations that propagate in the earth.
Double experience
To demonstrate this, the researchers carried out two experiments. In the first, they installed the tokay on a platform, which they made vibrate, and placed electrodes on the animal’s skull. Thus they were able to observe the activation of neurons in an area at the back of the brain called the “oval vestibular nucleus.” They confirmed this direct relationship by injecting dye into the nerves exiting the saccule and following their progression using imaging. During this second experiment, the dye spread to the vestibular nucleus, then continued to the auditory cortex, located at the top of the brain stem. “A very beautiful, very rigorous demonstration.greets Anthony Herrel, CNRS researcher at the National Museum of Natural History in Paris and specialist in reptiles. It invites us to rethink our vision of reptiles, of the way they perceive the world. »
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