Neural differentiation in fly CNS transplants cultured in vivo

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Abstract
To study the influence of afferent retinal innervation on neuronal organization in the CNS during differentiation in the fly Sarcophaga bullata, we transplanted larval CNS with or without eye imaginal discs into freshly pupariated animals. After metamorphosis and eclosion of the adult flies, the transplants were recovered and analyzed histologically.Optic lobes transplanted with eye disc differentiated fully like normal in situ optic lobes. In transplants without discs the outermost optic neuropil, the lamina, did not differentiate at all, and the more central ones, medulla, lobula, and lobula plate, were reduced in volume. Although certain neuron types present in normal optic lobes could be identified, the strict columnar and layered organization of these neuropils was no longer apparent in the eyeless transplants.The experiments confirm the earlier notion that afferent innervation strongly influences normal differentiation in the peripheral optic lobes of insects, whereas more central neuropil regions are less dependent on the retinal innervation. In addition, we show that the formation of the normal pattern of dendritic arborizations as well as strict columns and layers in these lobes seems to require retinal and/or laminar input.