Worm With No Ears Can "Listen" to Sound, Offers New Tool for Studying Sensory Biology

Caenorhabditis elegans is a species of roundworm that is widely used in biological research. A recent study from the University of Michigan Lab Science Institute reveals that despite a lack of ear-like organs, this worm can sense and respond to sound.

The study, titled "The Nematode C. Elegans Senses Airborne Sound," published in the journal Neuron, offers a new tool for studying sensory biology, particularly the genetic mechanism underlying the sense of hearing.

Earless Worm Has Five Senses Except Hearing

Fifteen years ago, scientists believed that C. elegans only had three primary senses, which are the sense of taste, touch, and smell. But as Techzle reported, researchers in the lab of Shawn Xu have studied the worm for many years and found that they can sense light despite having no eyes.

Moreover, further research revealed that C. elegans has proprioception, or the ability to sense one's position. That means this worm can perceive its body's position while moving.

Despite these five senses, wherein the two were just recently discovered, Xu said that this species of roundworm lacks the sense of hearing. They do not have ear-like organs to help them hear.

But his team recently made a remarkable discovery about these earless worms. They found out that C.elegans hear sounds unlike any other species within the animal kingdom. The sense of hearing is only discovered in some anthropods and vertebrates, which means that most invertebrates are not sensitive to sounds.

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C. elegans' Whole Body Act as a Cochlea to Sense Sounds

According to Phys.org, Xu's team discovered that the worm could sense and respond to airborne sounds in the range of 100 hertz to 5 kilohertz despite not having ears. They conducted several experiments to see how the worm would respond to airborne sound waves and not rely on vibrations from where it was resting.

The team believes that the worm could sense sound waves at that range because it quickly moved away from the sound source. That means that they can both sense the source and hear the sound. Xu added that the worm itself acts as a whole-body cochlea, a part of the inner ear of vertebrates that translates vibrations into nerve impulses.

Biocompare reported that the worm has two types of auditory sensory neurons that are connected to its skin, so when sound waves bump to them, the skin detects the vibration that may cause the fluid inside the worm's body to vibrate similarly to how fluids in the cochlea vibrate when detecting sounds.

Moreover, the worm can detect the sound source based on which of the two types of neurons are activated. This helps them detect and evade potential predators, which generate sounds when hunting.

This recent discovery suggests that other earless invertebrates like C. elegans, like flatworms, mollusks, and earthworms, might also sense and respond to sound via their skin. More so, it reveals key differences from how vertebrates and arthropods sense sounds.