Cell lineage relationships in the imaginal wing disc of Drosophila melanogaster

Abstract

An account is given of the patterns of cell lineage in the wing and mesonotum, the derivatives of the imaginal wing disc of Drosophila melanogaster. The system was analyzed using somatic crossing over, induced by X-rays at specific stages of development. Clonally related cells occupy longitudinal stripes in the wing, and this is interpreted to mean that cell divisions are oriented in the developing disc. Clonally related cells occupy irregularly shaped areas in the mesonotum, but some nonrandomness is detectable. The data indicate that, in the embryo, presumptive wing disc cells are not determined as between upper wing, lower wing, and mesonotum. In the larva, however, the anlagen of these three structures are represented by separate populations of proliferating cells within the disc. These groups of cells have distinct rates and patterns of cell division. The data were used to estimate cell numbers in the three parts of the disc at various stages of development. It appears that the growth rates of the parts of the wing disc are constant throughout larval development. The results are discussed in relation to problems of morphogenesis in imaginal discs.