This project will examine the potential cues that initiate and maintain swarm behavior in the marine copepod, Dioithona oculata, by computerized motion analysis to study individual and swarm responses to light intensity and pheromones. A conceptual model is presented for the swarming behavior pattern: diel light cycles provide a releasor cue, a threshold light intensity provides an arousal cue, and gradients of light intensity elicit a swarming response. Cues for individuals to orient in the swarm may be light intensity, and/ or pheromones. The study will first determine photosensitivity by phototaxis, and response to chemical pheromone signals by recording individual swimming tracks. The swimming behavior and spatial distribution of individuals in a swarm will be quantified for laboratory swarms in experimental light gradients, changes in light intensity, and presence of a swarm marker (beam of light). The life history stage composition of laboratory swarms will be manipulated to test for the effect of pheromones from adult females and other swarming stages. Laboratory swarm behavior will be compared to that of field swarms. Initially all experiments will be conducted during midday until the presence or absence of circadian rhythms has been determined. This study will help verify the conceptual model of swarm behavior, provide a framework for interpreting in situ observations of zooplankton aggregation, and provide mechanisms for explaining swarming which can be included in mathematical models.
