Influence of fast advective flows on pattern formation in Dictyostelium discoideum*

A classic example of self-organized patterns in nature is found in the social amobae Dictyostelium discoideum. We present experiments on pattern formation of Dictyostelium discoideum in the presence of fast advective flows. We observe wave trains that propagate both parallel and perpendicular to the flow direction. While the transverse wave velocity and the wave period are constant, the downstream wave propagation velocity scales linearly with the imposed flow velocity. We show that the acquired wave shape is highly dependent on nucleation point of the wave as well as on the strength of the advective flow. We compare the experimental results with numerical simulations performed using a Reaction-Diffusion model and found excellent agreement. Additionally we show that a Reaction-Diffusion model with fast dynamic assumptions does not reproduce the observed results. These results are relevant to understand the process of pattern formation and aggregation of Dictyostelium discoideum that may experience fluid flows in its natural habitat.