THE SWARMING BEHAVIOR OF THE COPEPOD DIOITHONA-OCULATA - IN-SITU AND LABORATORY STUDIES

The behavior of the swarm-forming copepod Dioithona oculata was studie d both in situ and in the laboratory using a video-computer system for motion analysis. In nature, swarms form in light shafts between the p rop roots of red mangroves. Swarms maintain their position within thes e light shafts despite currents of up to 2 cm s(-1). In the laboratory , swimming speeds and turning rates of swarming copepods in still wate r were lower than those observed in the held. Copepods studied in a fl owthrough chamber in the laboratory had swimming behaviors similar to those observed in nature; the stimulation from water movement caused i ncreases in both swimming speed and rate of change of direction. Incre ased current speeds also caused the swarms to become more tightly pack ed within the center of a vertical light shaft. Nonswarming copepods w ere unable to maintain their position in a current in darkness. In lab oratory experiments, the presence of actively feeding planktivorous fi sh caused swarms to temporarily disperse due to escape responses of th e copepods. However, planktivorous fish were rarely observed feeding o n swarms in nature, perhaps due to the presence of predatory fish hidi ng among the prop roots.