FEEDING MICROSTRUCTURE APPROACHING CESSATION IN LARVAL MANDUCA SEXTA: EFFECTS OF SATIATION, IMMUNE CHALLENGE, MOLTING, AND PREDATOR STRESS.

Abstract

As animals approach satiation, their motivation to feed decreases. However, there are a variety of factors other than satiation that can affect feeding motivation. The tobacco hornworm caterpillar, Manduca sexta, is an ideal system for studying feeding motivational physiology. It shows no circadian rhythm in its feeding and has a relatively simple nervous system. It reduces feeding when ill, exposed to model predators, and during certain developmental periods. It reduces feeding when approaching a developmental molt, as in other larval insects. The stress from a predator can also reduce feeding. The force with which an animal bites during feeding has been linked to feeding motivation in many other species. By noninvasively measuring the force applied to food during feeding, changes in M. sexta motivation can be examined across a feeding period and between different conditions. Understanding how this caterpillar terminates a self-generated behaviour such as feeding, provides insight into the regulation of motivation.