Modeling the locomotion of Caenorhabditis elegans: Undulatory propulsion and maneuverability in fluids

This dissertation presents novel theoretical models for reproducing and analyzing the motion of free-living nematode Caenorhabditis elegans. Due to its simplicity and wealth of anatomical knowledge, this organism has become a powerful biological platform for performing a wide range of studies involving genetics, neuroscience, and behavior. Understanding the locomotion of C. elegans is of utmost importance, as the analysis and classification of nematode motion can be used as direct readout of the animal’s behavior. To provide further understanding of the mechanics of nematode locomotion, this work provides theoretical tools to efficiently model the motion of C. elegans in different environments, such as confined and unconfined fluids. Making use of preexisting mathematical descriptions for reproducing nematode gaits in two-dimensions, this study incorporates accurate hydrodynamic models to analyze the swimming motion of the animal, and evaluate its performance in terms of swimming speed, propulsive power optimization, and maneuverability in fluids. Furthermore, this work also generalizes previous models of nematode gait to three-dimensional space. Simulations accurately predict worm shapes corresponding to the maximum swimming speed as well as the optimal swimming gaits that maximize speed while minimizing propulsive power. Additionally, detailed analyses of the motion of C. elegans reveal what mechanisms are involved in efficient maneuverability of the animal in fluids.

This work also presents two independent studies elucidating how C. elegans interact with the surrounding environment and behave in the presence of chemoattractants. The first study explores the dynamics of swimming nematodes approaching a flat solid interface and aims to better understand what mechanisms are involved in the conglomeration of nematodes near solid boundaries. Such knowledge has the potential to aid in the improvement of devices used to sort nematodes.

The second study evaluates the chemotactic performance of swimming nematodes in 3D, and investigates how chemical sensing translates into observable behavior. In the framework this model, the sensory response was evaluated through direct measurements of the chemotactic performance of burrowing and swimming nematodes. Simulation results reveal that, in addition to chemical sensing, environmental conditions greatly contribute to the chemotactic performance of C. elegans. These results may provide a means of validating artificial neural systems through direct comparisons against the chemotaxis model.