Adult deficiencies and duplications of head and thoracic structures resulting from microcautery of blastoderm stage Drosophila embryos.

Drosophila embryos were damaged by microcautery at the cellular blastoderm stage at the sites of presumptive imaginal cells, identified from fate maps. The resulting adults were analyzed for abnormal structures. Cautery of any of the presumptive imaginal regions can lead to defects in the adult cuticle, though the majority of adults which hatch are morphologically normal. The abnormal adults had one or more discs either deleted, incompletely formed, or misarranged. Several of the structures which were incomplete had duplicated regions. The results suggest that, from the time fo their initial formation in the cellular blastoderm, a group of cells determined to be an 'adult' structure possesses a gradient of developmental capacity which is expressed by certain regions duplicating and other cells regenerating. The types of duplications found were similar to those resulting from other experimental treatments of imaginal discs at later stages in development, indicating that the presumptive imaginal disc cells, when they are first established in the cellular blastoderm, have a similar organization to mature imaginal discs.