Self-organization of tubular networks by fluid flows

Long-ranged dynamic patterns are important for development and functioning of large-scale organisms. In the tubular networks of plasmodial slime molds the tubes’ periodic contractions organize in a traveling wave on scales of up to several centimeters. What drives communication across the network? What drives the self-organization of the tube’s cortex to form long-wavelength patterns? Searching for the mechanism of signal propagation we find that flows are hijacked by signals to propagate through the network. Signals promote their own transport by invoking a propagating front of increased flow. This mechanism is sufficient to explain complex dynamics of the organism like finding the shortest path through a maze. Importantly, we find that distant parts within the tubular network communicate by fluid flow. We investigate the mechanism behind the self-sustained contractile waves by developing a minimal model, coupling the mechanics of a cell’s cortex to a contraction-triggering chemical. The chemical itself is spread with the fluid flows that arise due to the cortex contractions. Through theoretical and numerical analysis, we find that the oscillatory component of the flows can give rise to robust scaling of contraction waves with system size—much beyond predicted length scales.