Synergistic genetic interactions between ecdysis and local dendrite pruning pathways. (A–C) C4da neurons were labeled with ppk-CD4::tdtomato and dendrite pruning phenotypes were assessed at 16 h APF. (A) Animal heterozygous for the mical mutant allele swp2^MICAL. (B) Animal expressing UAS-hid under CCAP-GAL4 to ablate CCAP neurons. (C)swp2^MICAL heterozygote with ablated CCAP neurons. (D) Penetrance of neurons with dendrite severing defects in A–C. *P < 0.05, **P < 0.005, two-tailed Fisher’s exact test, N = 48–69 neurons. (E) Length of unpruned dendrites in A–C. Values are mean ± SEM, **P < 0.005, Wilcoxon-Mann-Whitney test. (F–H) Ecdysis inhibition causes phagocytosis defects during dendrite pruning. C4da neurons were labeled by pHluorin-CD4-tdtomato expression under the ppk promotor (ppk-MApHS), and pHluorin/GFP and tdtomato fluorescence was assessed at 14 h APF. (F–F″) C4da neuron in control animal. (G–G″) C4da neuron in animal with ablated CCAP neurons. (H) Length of pHluorin-positive (severed and unsevered) dendrites in F and G. Values are mean ± SEM, ***P < 0.0005, Wilcoxon-Mann-Whitney test, N = 27 each. (I–K) C4da neurons were labeled with ppk-CD4::tdtomato and dendrite pruning phenotypes were assessed at 18 h APF. (I) Animal heterozygous for drpr^Δ5, wsp¹ mutant alleles. (J) Animal expressing UAS-hid under CCAP-GAL4 to ablate CCAP neurons. (K)drpr^Δ5, wsp¹ heterozygote with ablated CCAP neurons. (L) Penetrance of dendrite severing defects in I–K. *P < 0.05, **P < 0.005, two-tailed Fisher’s exact test, N = 40–47 neurons. (M) Length of unpruned dendrites in I–K. Values are mean ± SEM, ***P < 0.0005, Wilcoxon-Mann-Whitney test. Scale bars in A, F, and I are 50 μm.