Worms Have the Ability to Identify Thousands of Different Smells; Scientists Discover Mystery Behind This Sniffing Skill

For decades, scientists have been puzzled about how worms can differentiate between more than 1,000 unique scents.

As indicated in a SciTechdaily report, for soil-dwelling nematodes that rely mainly on olfaction for survival, the ability to smell or not smell "may be different between life and death."

The University of Toronto researchers have now identified the molecular mechanisms behind this process and have demonstrated that it comprises the conserved protein that helps to equilibrate human eyesight.

The team's finding has impacts beyond nematode olfaction and may even shed light on how human brains are functioning.

Worms' Sense of Smell

Professor of molecular genetics Derek van der Kooy from the Temerty Faculty of Medicine, the University of Toronto, who's also director of Donnelly Centre for Cellular and Biomolecular Research, is the study's lead researcher.

Furthermore, the worm Caenorhabditis elegans is one of the model organisms used in the neuroscience research carried out at the van der Kooy lab.

The findings were recently published in the Proceedings of the National Academy of Sciences journal.

According to the study's first co-author and newly minted Ph.D. graduate Daniel Merritt from the van der Kooy lab after his thesis defense last week, the worms have an "incredible sense of smell," which is amazing.

C. Elegans

He added that they could identify quite a variety of compounds like molecules released from soil, flowers, bacteria, and fruit. More so, they can even smell cancer biomarkers and explosives n the patients' urine.

Essentially, C. elegans is a champion sniffer due to its possession of roughly 1,300 odorant receptors whose discovery started 30 years ago.

Similar to humans, who possess roughly 400 receptors, each receptor is dedicated to sensing a single type of smell, although this is where similarities end.

Huan noses are lined with hundreds of sensory neurons expressing just one receptor type. More so, when an odorant stimulates a given neuron, the signal travels deeper into the brain along its long process, or axon, where it is perceived as scent or odor.

Smell discrimination is stimulated by the axonal cables' separation carrying different smell signals.

The worms have only 32 olfactory neurons, holding all their 1,300 receptors. Merritt explained that the one neuron-one smell technique "is not going to work here."

GPCRs Expressed

The finding, a related Phys.org report specified, is significant as it is the first evidence that shows the arrestin can fine-tune numerous sensations.

Describing the findings, Merritt said there is no case known in biology before this where arrestin is employed to enable discrimination of signals outside the cell.

He added that the same mechanism could play out in other animals when numerous GPCRs are expressed on the same cell, particularly in the brain.

Essentially, the brains are bathed in neurochemicals that signal through hundreds of different GPCRs, raising the probability that arresting, of which there are four different types in humans, could be key for processing information.

The work provides a single piece of the puzzle of how the amazing sense of smell of worms works, although it informs the understanding as well of how GPCR signaling works "more broadly within animals," Merritt concluded.

Related information about C. elegans is shown on OpenWorm's YouTube video below:

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