| The optic lobes of Drosophila melanogaster have much to offer as a system in which to study neural development. The structure of the optic lobes reflects the arrangement of photoreceptors in the retina, and normal structure requires innervation from the eye. Cells giving rise to these structures proliferate throughout larval life, begin to differentiate and make connections during the late larval stage, and continue to develop throughout metamorphosis. Adult optic lobes consist of three discrete ganglia, connected by two chiasms. Their highly regular and repetitive structure simplifies the task of identifying defects in this tissue.;Three major topics are presented here. First, a review of optic lobe structure and development is given, as well as a brief study of normal optic lobe development. Adult structure is illustrated with reduced silver impregnations of sectioned heads. Optic lobe development is examined primarily by the use of novel insertions of an enhancer detector which express in this tissue. Several staining methods are employed as well. Second, an intensive investigation of a mutation causing structural defects in the optic lobes is detailed. The mutation was isolated using an behavioral assay for flight ability. Details of the structural defects and their onset during development are presented. The behavioral defects are characterized. The mutation has been localized and reverted, and a preliminary molecular analysis has been undertaken. The third topic is a survey of patterns of gene expression in the optic lobes using enhancer detection. The insertion lines are categorized according domain of expression during the third larval instar. Examples of some of these categories are examined during development. An analysis of variation within a few categories is made. |
