How to Search Space using Active Filaments

Searching space is key for organisms to find food, mates and suitable ecological niches. But how does one search when one is very small and stuck in place? The ciliate Lacrymaria olor presents a striking example of such a "search" behavior wherein a single-cell rapidly extends a neck-like protrusion to several times its body size to dynamically and efficiently hunt for prey in its surrounding space. Inspired by this remarkable behavior, here we present a framework for how cells search by combining experiments using the ciliate Lacrymaria olor, and a physical model based on deformable active filaments: i.e. filaments capable of exerting active hydrodynamic stresses on the surrounding fluid. Using our model we show that the "self-deforming activity" of these filaments can lead to complex filament dynamics even with simple patterns of underlying activity. Exploring how this dynamics depends on filament parameters such as length, stiffness and activity time-scales allows us to identify distinct regimes where effective "search" behaviors can emerge. Our model and results serve as the starting framework for understanding how the behavior of biological and man-made systems at the microscale can be programmed through the interplay of motility and morphodynamics.