BEHAVIORAL MODES ARISE FROM A RANDOM PROCESS IN THE NUDIBRANCH MELIBE

Stochastic analysis was applied to observations of spontaneous behavio r in the carnivorous mollusc Melibe leonina. Six behaviors were define d that could be easily recognized on inspection and it was found that transitions between each of these behaviors could be fully described b y a first-order random process without memory of past behavioral choic es, The behaviors are organized by frequency of transition into two mo des, a feeding mode and a resting mode. Transitions within modes are m ore likely than transitions between modes, and the feeding and resting modes are linked by a preferred pair of behavioral transitions. The a mount of time spent in the feeding mode is positively correlated with body size, but the average length of a feeding episode is independent of size, This suggests that body size regulates the probability of ent ry into feeding behavior but does not influence the basic pattern of f eeding, In the presence of food the animals express nearly continuous feeding behavior, suggesting that food reduces the probability of exit ing the feeding mode. This model of spontaneous behavior in Melibe is used to form hypotheses amenable to further exploration through neurop hysiological experiments.