Daily variation of multiple behaviors in Aplysia fasciata: Integration of feeding, reproduction, and locomotion

Abstract

Daily variations in feeding, reproductive behaviors, and activity level were examined under three conditions: (1) animals had access to food and mates; (2) there was access only to food; (3) neither food nor mates were present. Behaviors differed in amplitude of variations from their daily mean value. Egg-laying had the strongest tendency to be clustered. Amplitude of variations in courtship and swimming was larger than those of immobility, crawling, and feeding, while moving in place was the least clustered behavior. Changes in state affected the tendency to be clustered. When food and mates were present, amplitude of variations became progressively larger for immobility, moving in place, crawling, and swimming. Behaviors differed in the degree to which variations were patterned as a 1/day oscillation. Relatively little of the variability in crawling, moving in place, courtship, and egg-laying was due to a 1/day oscillation under any condition. By contrast, a large proportion of the variability of immobility, swimming, mating, and eating was modulated by a 1/day oscillation in at least one condition. The contribution of a 1/day oscillation to variability differed in the conditions examined. For immobility and swimming, when food and mates were present, the 1/day component of variability became smaller. By contrast, presence of mates led to an increase in the 1/day component of variability modulating feeding. Daily peaks of swimming and feeding were in phase with one another, and out of phase with mating and feeding. The ratio of locomotion to inactivity is constant, independent of change in external conditions. However, this ratio varied throughout the day. When food and mates were absent, variations of immobility and swimming were strongly related to variations in the inactivity ratio. When food and mates were added, this tendency decreased. The data suggest that daily variations in occurrence of behaviors can be accounted for by interactions between oscillators affecting Aplysia behavior and motivational variables. A 1/day oscillator has strong effects on mating, swimming, and immobility. The effect of the oscillator is modified by changes in motivational state.