A Mechanosensory Circuit in Drosophila Larva Revealed by Electron Microscopy Reconstruction
(A) Schematic of the mechanosensory (Me) Chordotonal neurons and the nociceptive multidendritic class IV neurons, projecting their axons from the periphery to the VNC. Insets illustrate their morphology in the body wall. Vibration activates the Me neurons and elicits bending and hunching. Noxious stimulus activates the nociceptive neurons and elicits a rolling escape response.
(B) EM imaging and reconstruction reveal fine morphology and synaptic connectivity.
(C) Synaptic connectivity diagram of preferred local interneuron partners of the Me neurons (Jovanic et al., 2016; Ohyama et al., 2015). Strong activation of the excitatory multisensory Basin (Bs) triggers rolling; weak activation triggers bending and hunching. Inhibitory Drunken (Dr), Griddle (Gr), and Ladder (Ld) interneurons trigger bending and hunching though disinhibition. “Other,” less strongly connected (dashed arrows) interneurons. Circles, neuron type. Dark arrows, connections that are analyzed in this study. Thickness of solid arrows, connectivity strength. Only connections greater than 1% of postsynaptic input in each hemisegment are shown.