C. elegans senses its physical environment to adapt its movement

Caenorhabditis elegans, a one-millimeter-long worm, is commonly used as a model animal to study mechanosensation, the ability of animals to detect and convert mechanical forces (such as touch, pressure, or stretch) into electrical signals that the brain can interpret.

Touch receptor neurons (TRNs), located along the animal’s body wall, were long thought to passively sense simple touch stimuli as they occurred, triggering the corresponding avoidance response. Now, a team of ICFO researchers, Dr. Aleksandra Pidde, Dr. Montserrat Porta de la Riva, Dr. Costanza Agazzi, Dr. Carmen Martínez Fernández, Alice Lorrach, Dr. Neus Sanfeliu Cerdán and Dr. Alba Calatayud Sánchez, led by ICFO Prof. Michael Krieg, and in collaboration with the Centre Internacional de Mètodes Numèrics en Enginyeria (CIMNE) and the Universitat Politècnica de Catalunya (UPC), has shown in a Nature Communications study that these receptors can also detect velocity-dependent forces, such as the friction exerted by the surface on which the worm crawls. This means that the worm can generate movements to actively gather sensory information about its environment, rather than merely receiving input passively.

“When an organism moves, it needs to feel the surface. Without this feedback, we barely can walk and maintain posture – a feeling we experience when our legs fall asleep,” explains Prof. Michael Krieg, lead author of the article. “Crawling animals also use this proprioceptive feedback, gathered through specialized mechanoreceptors, to optimize the energy spent during locomotion.” As a result, the worm's body wall is constantly sensing how fast it's moving and how much resistance it encounters from the surface, allowing it to move efficiently and adapt to changing environments.

In particular, the researchers have identified a previously unknown behavioral function for PVM, one of the six neurons responsible for sensing gentle mechanical stimuli in C. elegans. This neuron appears to selectively sense soft substrates and send this information to proprioceptive neurons –neurons that sense the position and movement of the animal’s own body–, so that the worm can adjust its posture and movement in a similar way to how plantar mechanoreceptors in our feet work.

This connection between mechanoreceptors and proprioceptors was further exemplified by studying mutant C. elegans with disrupted MEC-4 activity (a specialized protein that helps the worm detect mechanical forces and convert them into electrical signals). These specimens displayed lethargic behavior and reduced mobility, suggesting that the ability to detect and transmit mechanical input is vital for efficient movement.

Overall, the study shows for the first time that body-substrate contact plays an important role in spatial navigation in eye-less animals as they move.

Reference:

Pidde, A., Porta-de-la-Riva, M., Agazzi, C. et al. Mechanosensory encoding of surface mechanics optimizes locomotion. Nat Commun 17, 9083 (2026).

DOI: https://doi.org/10.1038/s41467-026-75352-7

Acknowledgements:

AP acknowledges financial support from Grant FJC2021-047089-I funded by MCIN/AEI/10.13039/501100011033 and by the European Union "NextGenerationEU/PRTR", MK acknowledges financial support from the Human Frontiers Science Program (RGP021/2023), MCIN/AEI/10.13039/501100011033/ FEDER “A way to make Europe” (PID2024-157334OB-I00, CNS2022-135906), “Severo Ochoa” program for Centres of Excellence in R&D (CEX2024-001490-S)[MICIU/AEI/10.13039/501100011033], from Fundació Privada Cellex, Fundació Mir-Puig, and from Generalitat de Catalunya through the CERCA and Research program. ICFO is the recipient of the Severo Ochoa Award of Excellence of MINECO (Government of Spain). JJM and AB acknowledge Severo Ochoa program (CEX2018-000797-S). JJM is also financially supported by grant PID2020-116141GBI00 funded by MCIN/AEI, and grant SGR 01049 from the local government Generalitat de Catalunya.