Fig. 3: Morphological changes and connectional changes are mutually associated.

a EM cross-section view (left) and 3D volumetric reconstructions of presynaptic and postsynaptic neurons (middle) at the location of ASG-ASI contact where synapse exists (right, contact area marked as white) in adult-2 (top row) and dauer (bottom row). Contact area between ASG and ASI was significantly larger in dauer resulting in dauer-specific synapses (yellow arrows). Note that EM cross-section views of two stages may look different as two datasets have been sectioned in different orientations. b Same with a for ASG-AIA contact. ASG-AIA contact area is significantly reduced in dauer while ASG-AIA contact area is distinctive resulting in larger synapse (yellow arrow). c Wiring diagram of neurons shown in a and b in adult-2 stage (left) and dauer stage (right). Width and color of the arrow follows the same rule from Fig. 2d. Larger contact between ASG and ASI results in strong reciprocal connections and smaller contact between ASG and AIA results in no connection in dauer. d Same with a for RIC-IL1 contact. IL1-RIC contact exists in the dauer stage while they do not make contact in the adult-2 stage resulting in dauer-specific synapses (yellow arrows). e Same with a for RIC-AVA (light blue) and RIC-AVB (white) contacts. Area of RIC-AVA contact decreased in the dauer stage, leading to lack of synapses in the dauer stage while RIC-AVA synapses (yellow arrows) exist in the adult-2 stage. Area of RIC-AVB contact increased in the dauer stage resulting in dauer-specific synapses (yellow arrow). f Wiring diagram of neurons shown in d and e in adult-2 stage (left) and dauer stage (right). Contact between RIC-IL1 and RIC-AVB results in new connections and lack of contact between RIC-AVA results in no connection in dauer. a–e Scale bars: 500 nm (EM images) and 1 μm (3D views), asterisk: active zone, yellow arrow: stage-specific synapse.