Figure 2.

General model of body and imaginal disc growth in Drosophila. (a) The growth of the body and imaginal discs under optimal nutritional conditions. See main text for details. (b) A reduction in nutrition slows growth and delays attainment of critical size, extending total developmental time. Attainment of critical size initiates the same hormonal cascade that brings about the cessation of body and imaginal disc growth. The temporal dynamics of this cascade are unaffected by nutrition. Slow growth of the body and imaginal discs now reduces the amount of growth they can achieve during their TGPs, reducing final body and organ size. Hormones other than ecdsyteroids may be involved in the cessation of disc growth. L1–L3, first to third larval instar; TGP, terminal growth period.