Calcium Taste Avoidance in Drosophila.

Many animals, ranging from vinegar flies to humans, discriminate a wide range of tastants, including sugars, bitter compounds, NaCl, and sour. However, the taste of Ca is poorly understood, and it is unclear whether animals such as Drosophila melanogaster are endowed with this sense. Here, we examined Ca taste in Drosophila and showed that high levels of Ca are aversive. The repulsion was mediated by two mechanisms-activation of a specific class of gustatory receptor neurons (GRNs), which suppresses feeding and inhibition of sugar-activated GRNs, which normally stimulates feeding. The distaste for Ca, and Ca-activated action potentials required several members of the variant ionotropic receptor (IR) family (IR25a, IR62a, and IR76b). Consistent with the Ca rejection, we found that high concentrations of Ca decreased survival. We conclude that gustatory detection of Ca represents an additional sense of taste in Drosophila and is required for avoiding toxic levels of this mineral.