JOINT REGULATION OF CELL-SIZE AND CELL NUMBER IN THE WING BLADE OF DROSOPHILA-MELANOGASTER

We used Drosophila melanogaster to test for compensatory control of ce ll area and cell number in the regulation of total wing area. In two r andom bred wild-type base stocks collected from different geographic l ocations we found a negative association between the area and the numb er of cells in the wing blade. Three replicate lines were selected for increased or decreased wing area, with cell area maintained at the sa me level as in the three controls. After eight generations of selectio n, despite a large and highly significant difference in wing area betw een the large, control and small selection lines, cell area did not di ffer significantly between them. Rather, the difference in wing area b etween selection regimes was attributable to differences in cell numbe r. Over the course of selection, the initially significant negative co rrelation between cell area and cell number in the wing increased, pro viding evidence for compensatory regulation of cell area and cell numb er. As a result of the increasingly negative association between the t wo traits, the variance in wing area declined as selection proceeded. It will be important to discover the mechanisms underlying the compens atory regulation of cell area and cell number.