Differential Coding of Fruit, Leaf, and Microbial Odours in the Brains of Drosophila suzukii and Drosophila melanogaster

Drosophila suzukii is a major pest that damages berries and stone fruits by laying its eggs in ripening fruit still on the plant, in contrast to its sister species Drosophila melanogaster, which lays its eggs on overripe, fermenting fruit on the ground. Both species rely on their sense of smell to find such fruit, but how their brains process these odours and subsequently decide on different hosts is not yet fully understood. In this study, we hypothesised that the differences in behaviour may begin in the antennal lobes, the first brain regions of the olfactory system. Using advanced brain imaging techniques, we investigated how the two species respond to odours of ripe fruit, fermented fruit, leaves, and bacteria. We found structural differences in the antennal lobes and differences in the way the odours are represented in these areas of the brain, while behavioural experiments looking for direct differences in the attractiveness of the tested odours revealed no significant variation between the species. The differences in odour processing could form the basis for alternative species-specific pest control strategies that could reduce dependence on insecticides.