Mechanical sensitivity of early pupal dendrites. (A–D) Mechanical stability of dendrites of white pupal (0 h APF [A–B′]) and pupal (5 h APF [C–D′]) dorsal c4da neurons as assessed by sensitivity to brief sonication in a water bath. A–D show dorsal c4da neurons before sonication, A′–D′ show the same neurons after 30 s sonication. (A and A′) White pupal control c4da neuron expressing Orco dsRNA. (B and B′) White pupal c4da neuron expressing Sox14 dsRNA. (C and C′) Control c4da neuron expressing Orco dsRNA at 5 h APF. (D and D′) C4da neuron expressing Sox14 dsRNA at 5 h APF. (E) Quantification of neurons with proximal dendrite regions containing thinnings and blebs in C and D. N = 24–25, ***P < 0.0005, two-tailed Fisher’s exact test. (F) Quantification of sonication-induced breaks in proximal primary and secondary dendrites. N = 24–25, *P < 0.05, **P < 0.005, two-tailed Fisher’s exact test. (G) Total number of breaks in proximal primary and secondary dendrites at 5 h APF before and after sonication. Values are mean ± SEM, N = 24–25, *P < 0.05, **P < 0.005, Mann–Whitney U test. Scale bars in A and C are 50 µm.