Fig. 3: ChAT-positive anal neurons in sea urchin larvae.

a The graph illustrates the number of anal neurons over time, showing the presence of approximately two neurons at the anus starting three days post-fertilization. (N = 3 batches [each consisting of a different male and female pair], n [2-day] = 4, 4, 3 larvae, n [3-day] = 6, 5, 6 larvae, n [4-day] = 8, 13, 3 larvae, n [5-day] = 4, 7, 3 larvae, n [6-day] = 8, 10, 10 larvae, n [7-day] = 7, 10, 8 larvae; [2 day] mean 0% ± 0% SEM, [3 day] mean 1.4% ± 0.1% SEM, [4 day] mean 1.9% ± 0.1% SEM, [5 day] mean 2% ± 0% SEM, [6 day] mean 1.9% ± 0.2% SEM, [7 day] mean 2.1% ± 0.1% SEM). b Immunostaining images of anal and intestine (yellow dotted-line) region with anti-SynB antibody (neurons) and anti-TroponinI (TnI) antibody (muscles). A rectangle indicated the magnified region shown in the right. The asterisks in the magnified view highlight the neurons. The schematic diagram presents a lateral view of the stomach and intestine. Magenta cells and green areas indicate neurons and sphincters, respectively, at anus. c–f Distribution of cholinergic neurons within the sea urchin larval intestine. d ChAT-neurons are not present around the pylorus. e Asterisks highlight neurons surrounding the anus. f Magenta cells in the schematic image depict ChAT-positive anal neurons. Scale bar in b =10 µm; c =20 µm. Source data are provided as a Source Data file.