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 cell area and cell number in the regulation of total wing area. In two random bred wild-type base stocks collected from different geographic locations we found a negative association between the area and the number of cells in the wing blade. Three replicate lines were selected for increased or decreased wing area, with cell area maintained at the same level as in the three controls. After eight generations of selection, despite a large and highly significant difference in wing area between the large, control and small selection lines, cell area did not differ significantly between them. Rather, the difference in wing area between selection regimes was attributable to differences in cell number. Over the course of selection, the initially significant negative correlation between cell area and cell number in the wing increased, providing evidence for compensatory regulation of cell area and cell number. As a result of the increasingly negative association between the two traits, the variance in wing area declined as selection proceeded. It will be important to discover the mechanisms underlying the compensatory regulation of cell area and cell number.