Neural reorganization during metamorphosis of the corpora pedunculata in Drosophila melanogaster

Abstract

Adult fruit flies and Drosophila larvae have very different bodies and behaviour patterns. The question therefore arises: how much reorganization does the brain undergo during pupation? Some apparent shape changes have been documented, for example, the growth of the optic lobes and the separation of the prothoracic and suboesophageal ganglia^1,2. In the central brain, the issue is less clear. Most neurone cell bodies persist through metamorphosis³, and the general shape of certain neuropil regions is conserved. However an identified motoneurone in another holometabolous insect (Manduca) has been shown to change its dendritic arborization patterns during pupation⁴. Here we report that the mushroom body, a major neuropil area in the insect brain, is extensively reorganized during pupation (that is, many of the intrinsic fibres are broken down and made anew). This reorganization is cryptic—the overall morphology of the mushroom body is apparently constant throughout pupation. We have now studied this reorganization by examining two mutations (mbd, mud) which cause derangement of this structure during metamorphosis, and we report that this reorganization is one of the most extensive yet found in insect metamorphosis.