PREDATORS CAN INDUCE SWARMING BEHAVIOR AND LOCOMOTORY RESPONSES IN DAPHNIA

1. Exposure to chemical cues released by fish induced a tendency to fo rm and maintain aggregations in two Daphnia clones originating from ha bitats inhabited by fish (and invertebrate predators), while Daphnia f rom a clone originating from a fishless habitat did not aggregate in r esponse to fish cues. 2. Daphnia from one of the two clones responsive to fish cues, also aggregated in response to chemical cues released b y invertebrate predators or to a substance released from homogenized D aphnia. 3. Chemical cues released by predators and the substance relea sed from homogenized conspecifics induced a significant decrease in Da phnia's swimming speed and an increased readiness to perform a somersa ulting escape behaviour, especially in response to light cues.