Fig. 5

Development of the serotonergic nervous system of M. japonica. Green: 5-HT-like immunoreactivity; blue or purple (B”): cilia, acetylated tubulin immunoreactivity; cyan: nuclei labeled with DAPI; red: muscles labeled with phalloidin. (A, A’) 48-hour-old larvae, a substack from dorsal view (A) and a substack lateral view (A’) showing apical neurons (an) leading to lateral neurons (ln) via lateral nerve cords. (B, B’, B”); 72-hour-old larvae, a substack from dorsal view (B), a substack from lateral view (B’), and a substack from dorsal view with higher magnification of apical neurons (B’). (C, C’) 5-day-old larvae, a substack from dorsal view (C) and a substack lateral view (C’) showing well-developed lateral nerve cords. (D) 7-day-old larvae with higher magnification of dorsal nerve commissure (dnc), an arrowhead pointing to the mouth opening. (E, E’, E”) 14-day-old larvae, a substack from dorsal view (E), a substack from dorsal view, with higher magnification of dorsal nerve commissure (dnc) and nerve processes of 5-HT-like immunoreactive cells running from cephalic nerves (cn) into the body wall (arrowheads pointing to cerebral organs) (E’) (E”), and magnification of posterior nerve ring pointed with an arrowhead, a substack from dorsal view (E”). (F, F’) 21-day-old larvae, a substack from lateral view (F) and a substack from ventral view, mouth opening (arrowhead) leading to foregut lumen (F’). Scale bars: 30 μm. Abbreviations: an, apical neuron; ap, apical tuft; co, cerebral organ; dnc, dorsal nerve commissure; fg, foregut; ln, lateral neuron; lnc, lateral nerve cord; mg, midgut; pc, posterior cirrus; pnc, posterior nerve commissure