Pharyngeal stimulation with sugar triggers local searching behavior in .

Foraging behavior is essential for all organisms to find food containing nutritional chemicals. A hungry fly performs local searching behavior after drinking a small amount of sugar solution. Using video tracking, we examined how the searching behavior is regulated in We found that a small amount of highly concentrated sugar solution induced a long-lasting searching behavior. After the intake of sugar solution, a fly moved around in circles and repeatedly returned to the position where the sugar droplet had been placed. The non-nutritious sugar d-arabinose, but not the non-sweet nutritious sugar d-sorbitol, was effective in inducing the behavior, indicating that sweet sensation is essential. Furthermore, mutant flies, which have no external taste bristles, showed local searching behavior, suggesting the involvement of the pharyngeal taste organ. Experimental activation of pharyngeal sugar-sensitive gustatory receptor neurons by capsaicin using the GAL4/UAS system induced local searching behavior. In contrast, inhibition of pharyngeal sugar-responsive gustatory receptor neurons abolished the searching behavior. Together, our results indicate that, in , the pharyngeal taste-receptor neurons trigger searching behavior immediately after ingestion.