(A) Optogentic activation of CsChrimson-expressing epidermal cells in the body wall triggers calcium transients in the axon terminal of GCaMP6s-expressing nociceptive SSNs. Images show responses from one representative animal. Plots depict mean GCaMP6s fluorescence intensity of the axon terminals of (B) C4da, (C) C3da, (D) Cho, and (E) C1da neurons following optogenetic activation (light stimulus, yellow box) of epidermal cells over time. Solid lines depict mean GCaMP6s fluorescence across replicates (n=15 larval fillet preparations), shading indicates SEM, red traces are GAL4+ ATR+, blue traces are GAL4+ ATR-, black trace is GAL4- ATR+. (F) The fraction of larvae exhibiting indicated behaviors during optogenetic epidermal stimulation in combination with SSN silencing via Tetanus Toxin (TnT) expression. We note that although baseline rolling probability is elevated in all genetic backgrounds containing the AOP-LexA-TnT insertion, silencing C4da and C3da neurons significantly attenuates responses to epidermal stimuluation. (G) The duration of the behavioral responses during optogenetic epidermal stimulation with neuronal TnT expression. Genotypes: (A-B) R27H06-LexA (C4da neurons), AOP-GCaMP6s, UAS-CsChrimson/+; R38F11-GAL4/+ or R27H06-LexA (C4da neurons), AOP-GCaMP6s, UAS-CsChrimson/+ (GAL4- ATR-effector-only control); (C) AOP-GCaMP6s, UAS-CsChrimson/+; R38F11-GAL4/NompC-LexA (C3da neurons); (D) UAS-GCaMP6s, AOP-CsChrimson, R61D08-GAL4 (Cho neurons)/R38F11-LexA; (E) UAS-GCaMP6s, AOP-CsChrimson, R11F05-GAL4 (C1da neurons)/R38F11-LexA; (F-G) R38F11-GAL4, UAS-CsChrimson, AOP-LexA-TnT/+ (Epi>CsChrimson); R38F11-GAL4, UAS-CsChrimson, AOP-LexA-TnT/ppk-LexA (Epi>CsChrimson + C4da>TnT); R38F11-GAL4, UAS-CsChrimson, AOP-LexA-TnT/NompC-LexA (Epi>CsChrimson + C3da>TnT).