Abnormal mushroom body plasticity in the Drosophila memory mutant amnesiac

In Drosophila melanogaster, adult or larval rearing conditions influence brain structure. In particular, larval density affects the number of fibers forming the mushroom bodies, a neuropil structure involved in olfactory learning. The mushroom bodies receive chemosensory inputs from the antennal lobes at the level of the calyx. In this study we report that larval density affects calyx volume measured shortly after eclosion from the pupal case. We observe that in the memory mutant amnesiac this form of experience-dependent structural plasticity is missing, whereas it is not affected in the learning mutant rutabaga and in the memory mutant radish. Independent of the plasticity effect, the calyces are on average slightly bigger than wild type in amnesiac and smaller in rutabaga flies.