Swimming and feeding by the scyphomedusa Chrysaora quinquecirrha

The semaeostome scyphomedusa, Chrysaora quinquecirrha (Desor, 1848), is an abundant and important planktonic predator in estuaries and coastal waters of the eastern USA during the summer. We videotaped free-swimming medusae in the laboratory and in the field in order to determine the relationship between swimming motions and prey encounter with capture surfaces. Medusae were collected from the Choptank River (Chesapeake Bay) in September 1992 and in the Niantic River, Connecticut, USA in July 1994. We used newly hatched Artemia sp. nauplii and fluorescein dye to trace water motions around swimming medusae. Swimming results in a pulsed series of toroids which travel along the medusan oral arms and tentacles. Prey are entrained in this flow and the location of naupliar encounter was influenced by the phase of the pulsation cycle during which entrainment occurred. Flow-field velocities, measured by tracking particles adjacent to the bell margin during contraction, increased with bell diameter. Received: 29 March 1997 / Accepted: 11 April 1997