Characterizing the effect of prey on swimming and feeding efficiency of the scyphomedusa Chrysaora quinquecirrha
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The scyphomedusa Chrysaora quinquecirrha (Desor, 1848) is an important predator in many coastal and estuarine systems of the eastern USA, but little is known of its swimming or feeding behavior. Medusae were collected from two tributaries of Chesapeake Bay, USA, in August–October 1998 and videotaped in three dimensions in a 10,000 l tank (diameter=2.4 m, depth=2.3 m). Their swimming patterns were dependent on the presence of prey. When prey were present, medusae decreased their pulsation rate by 17%, and increased their velocity and acceleration by 87% and 78%, respectively, as compared to when prey were absent. In addition, cyclical variations in each of these characteristics were prey dependent. When prey were absent, medusae altered their pulsation rate and velocity cyclically every 50–100 s. By contrast, when prey were available, pulsation rate and velocity varied every 18 s, and acceleration varied every 37 s. Medusae often were near the surface or bottom of the tanks regardless of the availability of prey, but swimming between these two locations was more frequent when prey were available. We attribute these prey-dependent changes in swimming to feeding behavior that minimizes energy expended while searching for and capturing prey in habitats where prey is heterogeneously distributed.
KeywordsFeeding Behavior Pulsation Rate Estuarine System Cyclical Variation Important Predator
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