It is critical for all animals to make appropriate, but also flexible, foraging decisions, especially when facing starvation. Sensing olfactory information is essential to evaluate food quality before ingestion. Previously, we found that <i>Drosophila</i> larvae switch their response to certain odors from aversion to attraction when food deprived. The neural mechanism underlying this switch in behavior involves serotonergic modulation and reconfiguration of odor processing in the early olfactory sensory system. We now investigate if a change in hunger state also influences other behavioral decisions. Since it had been shown that fly larvae can perform cannibalism, we investigate the effect of food deprivation on feeding on dead conspecifics. We find that fed fly larvae rarely use dead conspecifics as a food source. However, food deprivation largely enhances this behavior. We will now also investigate the underlying neural mechanisms that mediate this enhancement and compare it to the already described mechanism for a switch in olfactory choice behavior. Generally, this flexibility in foraging behavior enables the larva to explore a broader range of stimuli and to expand their feeding choices to overcome starvation.

Animals modify their behavioral outputs in response to changes in external and internal environments. We use the nematode, C. elegans to probe the pathways linking changes in internal states like hunger with behavior. We find that acute food deprivation alters the localization of two transcription factors, likely releasing an insulin-like peptide from the intestine, which in turn modifies chemosensory neurons and alters behavior. These results present a model for how inter-tissue signals to generate flexible behaviors via gut-brain signaling.

How does the presence or absence of food shape and prioritize behavioral decisions? When is food more than just food? As in other animals, prolonged food deprivation dramatically alters sensory behaviors in C. elegans. For instance, it has been known since the mid-1970s that hungry worms no longer respond to temperature changes in their environment, but the underlying mechanisms have been unclear. I will describe unpublished work showing that insulin signaling from the gut regulates thermosensory behaviors as a function of feeding state by engaging a modulatory sensorimotor circuit that gates the output of the core thermosensory network. C. elegans is associated with, and consumes, diverse bacteria in the wild. I will also discuss a recent story in which we find that in addition to providing nutrition, a bacterial strain in the worm gut alters the hosts’ olfactory behavior and drives food choice decisions by producing a neurotransmitter that targets the hosts’ sensory neurons. These results add to our growing body of knowledge of how signaling from the gut modulates peripheral and central neuron properties and drives sensory behavioral plasticity.