Genetic perturbations of autophagy and the Tor pathway affect developmental atrophy of persistent muscles. Short hairpin RNAs (UAS-shRNA) and the nuclear UAS-histone-mKO (red) reporter were co-expressed in muscles using the Mef2-Gal4 driver. Another fluorescent reporter MHC-tau-GFP (green) was used to label muscle cell bodies. (a) In a control pupa, persistent muscles in the 3rd abdominal segments undergo atrophy upon head eversion which is defined as time point zero hours. (b) Silencing of Atg9 by RNAi inhibits atrophy, resulting in enlarged muscle fibers compared to control. (c) Silencing of Tor enhances atrophy, leading to thinner fibers. (d) The effects of gene perturbations on muscle fiber diameter can be compared in time-series plots.