Long tentacles and oral arms alter feeding currents generated by the jellyfish Cyanea capillata

During development from larvae to adults, scyphozoan jellyfish undergo changes in morphology concomitant with the increase in Reynolds number of their fluid environment. Tentacles and oral arms develop as the wakes of cruise-foraging jellyfish become inertially dominant, characterized by vortices that induce feeding currents and transport prey to these trailing prey-capture surfaces. However, tentacles can reach far behind jellyfish, and it is unclear how effective these captures surfaces are when they extend past the vortex wake. Here we quantify changes in flow structures around a 50 cm, free-swimming robot model of Cyanea capillata with the addition of artificial tentacles and oral arms. We estimate the trade-off between decreased swimming efficiency and the increase in prey clearance rate that tentacles provide. Velocity fields measured with DPIV are used to identify changes in Lagrangian coherent structures (LCS) that transport prey to tentacles.