UC Riverside

In this work we examine the response of two Drosophila species to acids found in their natural food sources. We show that acids reduce normal gustatory behavior to sweet stimuli. We find that this acid aversion behavior is mediated by both the sweet and bitter neurons in the Drosophila taste system. Through electrophysiological studies we determine that acids inhibit neuronal firing to sucrose independently of bitter neuron input. We show that this inhibition can be overcome by increased sucrose concentration. We also find that acid inhibition of the sweet neuron is dependent on pH, regardless of the anion of the acid. Lastly, we examined the behavior of two members of the melanogaster subgroup, Drosophila sechellia and Drosophila melanogaster, to acids present in the main food source of Drosophila sechellia, morinda fruit. Behavioral studies showed that these two species diverge in their responses to morinda fruit and its component acids. Upon further examination we find that for some of the acids the behavioral difference can be attributed to a reduced sweet neuron inhibition in Drosophila sechellia. Thus we propose that sweet neuron inhibition plays an important role in behavior towards acidic stimuli.