Cost-benefit analysis potential in feeding behavior of a predatory snail by integration of hunger, taste, and pain

Hunger/satiation state interacts with appetitive and noxious stimuli to det ermine feeding and avoidance responses. In the predatory marine snail Pleur obranchaea californica, food chemostimuli induced proboscis extension and b iting at concentration thresholds that varied directly with satiation state . However, food stimuli also tended to elicit avoidance behavior (withdrawa l and avoidance turns) at concentration thresholds that were relatively low and fixed. When the feeding threshold for active feeding (proboscis extens ion with biting) was exceeded, ongoing avoidance and locomotion were interr upted and suppressed. Noxious chemostimuli usually stimulated avoidance, bu t, in animals with lower feeding thresholds for food stimuli, they often el icited feeding behavior. Thus, sensory pathways mediating appetitive and no xious stimuli may have dual access to neural networks of feeding and avoida nce behavior, but their final effects are regulated by satiation state. The se observations suggest that a simple cost-benefit computation regulates be havioral switching in the animal's foraging behavior, where food stimuli ab ove or below the incentive level for feeding tend to induce feeding or avoi dance, respectively. This decision mechanism can weigh the animal's need fo r nutrients against the potential risk from other predators and the cost of relative energy outlay in an attack on prey. Stimulation of orienting and attack by tow-revel noxious stimuli in the hungriest animals may reflect ri sk-taking that can enhance prey capture success. A simple, hedonically stru ctured neural network model captures this computation.