Fig. 2

The anterior neuroectoderm plays a crucial role in opening the pylorus. a Serotonergic neurons and pan-neurons recognized by Synaptotagmin B (synB) in sea urchin larvae. Green, serotonin; magenta, SynB; blue (DAPI), nuclei. b Serotonin induced pyloric opening in both control larvae and larvae without the ANE and pre-oral arms. The inset of each image shows the bright-field images. c The graph shows the opening rate of the pylorus in control larvae treated with seawater, in control larvae 2 min after the addition of serotonin, and in larvae without the ANE and pre-oral arms 2 min after the addition of serotonin. N = 3; n (with seawater) = 55, 79, 74; n (with serotonin) = 23, 11, 10; n (without the ANE and pre-oral arms and with serotonin) = 5, 8, 4. Error bars show SE. d The expression pattern of Go-Opsin (opn3.2) in Hemicentrotus pulcherrimus (arrows). e The activity of alkaline phosphatase in the gut was invariant in control and Go-Opsin morphants. f The graph shows the opening rate of the pylorus in control larvae and Go-Opsin morphants 2 min after photoirradiation or the addition of serotonin. N = 3; n (control; no treatment) = 45, 28, 22; n (control; photoirradiation) = 78, 63, 54; n (control; +serotonin) = 25, 49, 38; n (Go-Opsin morphants with no treatment) = 16, 14, 14; n (Go-Opsin morphants with photoirradiation) = 33, 32, 11; n (Go-Opsin morphants with serotonin) = 9, 51, 28. Error bars show SE. Scale bars in a, b, d, and e = 50 μm