Nematode behavior in disordered and deformable granular environments

Adaptive locomotion allows organisms to thrive in changing environmental conditions. While animals move through their environment, they also reshape it. We aim to charac­terize the locomotive adaptability and decision-making of nematodes as they travel through a quasi-two-dimensional layer of microparticles that form disor­dered and deformable packings, that resembles the granular texture of soil, one of nematodes’ natural habitats. We leverage the potential of the highly informative model organism C. ele­gans, which displays remarkable locomotive adaptability while steered by a compact nervous system, to iden­tify key neuromechanical requirements for adaptability with sensory feedback in granu­lar environment. We experimentally track both the locomotive behavior of C. elegans and the position of the sur­rounding parti­cles, using cus­tom­ized deep learning-based algo­rithms. We show that the packing density of particles and prior experience of nematodes affect the locomotive behavior of the latter, e.g., their traveling speed, frequency of turns, number of body bends, as well as the way moving animals interact with microparticles, e.g., crawling through or over a particle monolayer or opting for low dense areas. In addition, we analyze the impact that moving nematodes have on the granular medium. Our work sets the stage for the analysis of nematode behavior in a dynami­cally changing granular envi­ronment, con­tinuously shaped by the animal itself.