1b NMJs elevate evoked neurotransmission in a target-specific manner in the absence of 1s inputs. A–C, Representative EPSP traces of m6 (A), m12 (B), and m4 (C) in control (A8>GFP) and 1s-ablated (A8>GFP,hid,rpr) animals. Traces and graphs are color coded as indicated in the color key. D–F, Quantification of EPSP amplitudes in m6 (D; t(22) = 8.306, p < 0.0001, unpaired t test), m12 (E; t(22) = 13.82, p < 0.0001, unpaired t test), and m4 (F; t(29) = 3.057, p = 0.0048, unpaired t test) in control and 1s-ablated animals. G–I, Normalized EPSPs of m6 (G; t(25) = 2.301, p = 0.0300, unpaired t test), m12 (H; t(25) = 1.552, p = 0.1332, unpaired t test), and m4 (I; t(31) = 4.605, p < 0.0001, unpaired t test) in control and 1s-ablated third instar larvae. Normalized EPSPs in A8>GFP,hid,rpr are compared with the EPSP ratio of 1b/1b + 1s calculated from corresponding muscles in Figure 1I, indicated by gray dashed line. Note m6-1b slightly compensates, m12-1b does not compensate and m4 largely compensates the loss of 1s MNs. J–L, Normalized QC of m6 (J; t(25) = 1.239, p = 0.2268, unpaired t test), m12 (K; t(25) = 2.119, p = 0.0442, unpaired t test), and m4 (L; t(31) = 4.639, p < 0.0001, unpaired t test) in control and 1s-ablated larvae. Normalized QCs were compared with 1b baseline QC (see Materials and Methods). Note m4-1b shows an increased QC, while m12-1b shows a decrease. Error bars indicate ±SEM. *p < 0.05, **p < 0.01, ****p < 0.0001, ns - not significant. n values (NMJs/larva) are 12/9, 12/11, 12/9, 12/12, 14/11, and 17/14, respectively.