Study of earless worm's auditory capacity brings new tool into view for hearing research

 

sensory biology

© HeitiPaves - iStock

Fifteen years of careful study of the roundworm Caenorhabditis elegans has led scientists at the University of Michigan Life Sciences Institute (LSI) to this nematode's fascinating hearing sense: it picks up tones through neurones in its skin.

Shawn Xu's laboratory had worked out that, in addition to basic senses of touch, smell and taste, C. Elegans also senses light—despite not possessing eyes—and has proprioceptive recognition of its own movement and location. It was thought it might not be able to detect sound. "Hearing is unlike other senses, which are found widely across other animal phyla. It's really only been discovered in vertebrates and some arthropods. And the vast majority of invertebrate species are thus believed to be sound insensitive," said Xu, LSI research professor and lead author of a study earmarked for publication this autumn in the journal Neuron.

Xu and colleagues discovered, however, that C. Elegans responded to sounds in the 100 hertz to 5 Khz range, moving away from the source of the sound in experiments, indicating their tone detection also includes directionality. Additional experiments confirmed that the response was to airborne sounds rather than surface vibrations.

The worm's hearing mechanism

These worms hear through a kind of whole-body cochlea. Tightly woven into their skin and body are two types of auditory sensory neurones that react when the skin is vibrated by sound waves, while the fluid inside the work trembles in the same way as the fluid inside a cochlea. The auditory neurones are then activated and the vibrations translate into nerve impulses.

The immportance of this discovery

This research, which will now be taken further by Xu and colleagues, provides another pathway for exploring the hearing sense.

"This opens a whole new field for studying auditory sensation, and mechanosensation as a whole," he said. "With this new addition of auditory sensation, we have now fully established that all primary senses are found in C. elegans, making them an exceptional model system for studying sensory biology."

Source: EurekAlert!

P.W.