Worm drop experiment : Fluid like behavior of tangled worm assemblages*

California blackworms collectively show visco-elastic properties. We investigate the fluid-like behavior of the worms. Taking inspiration from the dripping faucet experiment with ants (1998) and the pitch drop experiment (1984), we set up a “leaky faucet” like experiment where the worms flow under the influence of gravity through a funnel. Due to pressure difference, the worms adapt the shape of a drop. As part of the drop detaches from the system, an elastic recoil in the remaining drop is observed. This recoil is analogous with a falling drop of water from a dripping faucet typically modeled by spring-mass models. Dripping faucet being an example of chaotic dynamical systems, we try to understand the system dynamics of the worm drop system. We characterize the return map of the drop interval and drop mass time series to explore any underlying structure in the highly nonlinear system dynamics. Finally, we explore the effects of activity of the individual worms on its effective fluid properties. We find that the viscosity of the effective worm fluid can be decreased by increasing the activity of the individual worms. These insights could improve our understanding of flow behavior in living active fluids and the mechanisms underlying their tuneable fluid mechanical properties.