Dynamics of \textit{C. elegans} in various fluidic environments

\textit{C. elegans} is a freely moving soil nematode that crawls or swims by propagating a body wave backwards. In fluids we investigate its swimming locomotion as the fluid viscosity is varied over many orders of magnitude and in the presence of non-Newtonian fluid responses. For Newtonian fluids we find power-law relations between swimming speed and fluid viscosity, and these relations are not in accordance with assumptions of constant power input to the fluid. We also find that the Strouhal frequency is nearly independent of viscosity and swimming speed. We investigate the influence of confinement on \textit{C. elegans} locomotion and find that interactions between confining walls and body undulations can markedly increase swimming speed.