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The specialized swimming behaviors described above for the hydromedusae increase their hunting efficiency considerably. However, even conventional “straight‐line” swimming creates flow fields around the swimming medusa that enhance prey capture. Analysis of movement in the disc‐like moon jelly Aurelia aurita shows that normal swimming motions, particularly the expansion of the swimming bell during the recovery stroke, entrain particles to within easy reach of the tentacles as the water rushes into the subumbrellar space (cf. Costello 1992).

Figure 3.18 Different hunting and feeding behaviors of medusae. Shaded areas indicate effective feeding spaces. (a) Motionless ambush strategy; (b) swimming‐sinking search pattern; (c) downward sinking with trailing tentacles creating vortices, which bring food particles within the feeding space; (d and e) two strategies employed by medusae such as Polyorchis penicillatus; part‐time swimming and fishing in the water column and part‐time resting on its tentacles on the bottom and capturing the prey directly with its manubrium.

Source: Adapted from Mills (1981).