Geckos use the saccule — a part of their inner ear traditionally associated with maintaining balance and body positioning — to detect low-frequency vibrations, according to a duo of biologists at the University of Maryland; this special ‘sixth sense’ plays a complementary role to the geckos’ normal hearing and the way they sense the world around them.
The tokay gecko (Gekko gecko). Image credit: Duncan Leitch.
“The ear, as we know it, hears airborne sound,” said University of Maryland’s Professor Catherine Carr.
“But this ancient inner pathway, which is typically linked to balance, helps geckos detect vibrations that travel through mediums like the ground or water.”
“This pathway exists in amphibians and fish, and now it’s proven to be preserved in lizards as well.”
“Our findings shed light on how the auditory system evolved from what you see in fish to what you see in land animals including humans.”
In their research, Professor Carr and her colleague, University of Maryland postdoctoral researcher Dr. Dawei Han, focused on tokay geckos (Gekko gecko).
They found that the geckos’ saccule can detect faint vibrations ranging from 50 and 200 Hz, a spectrum well below what geckos can usually hear through their ears.
This indicates that the saccule serves a distinct yet complementary function to the geckos’ regular auditory system.
While geckos can hear airborne sound, many other reptiles do not have that ability.
“The discovery of the saccule’s role in gecko hearing may lead to a better understanding of communication and behavior in other animals previously considered to have limited auditory capabilities,” said Dr. Dawei Han, a at the University of Maryland.
“A lot of snakes and lizards were thought to be ‘mute’ or ‘deaf’ in the sense that they do not vocalize sounds or hear sounds well.”
“But it turns out they could potentially be communicating via vibrational signals using this sensory pathway instead, which really changes the way scientists have thought about animal perception overall.”
The existence of this shared sensory pathway in modern reptiles offers a unique window into the evolutionary history of vertebrate sensory systems, suggesting that the transition from aquatic to terrestrial environments likely involved more complex and gradual changes in hearing mechanisms than previously thought.
Although these findings are not directly connected to how humans hear, the researchers believe that there’s always more than meets the eye — or in this case, ear.
“Think about when you’re at a live rock concert,” Professor Carr said.
“It’s so loud that you can feel your whole head and body vibrate in the sound field.”
“You can feel the music, rather than just hearing it. That feeling suggests that the human vestibular system may be stimulated during those loud concerts, meaning our sense of hearing and balance may also be linked closely.”
The findings were published in the journal Current Biology.
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Dawei Han & Catherine E. Carr. Auditory pathway for detection of vibration in the tokay gecko. Current Biology, published online October 4, 2024; doi: 10.1016/j.cub.2024.09.016
Source : Breaking Science News