Fig. S1. Brook and fourspine sticklebacks have canals and canal neuromasts. (A) Close-up dorsal view of a canal pore (solid arrowhead) in the supraorbital line (SO) line of a DASPEI-stained C. inconstans specimen. Note canal neuromasts (asterisks) below the plane of focus. Scale bar=0.75 mm. (B) Lateral view of a DASPEI-stained A. quadracus specimen showing large canal neuromasts beneath the skin (asterisks) and smaller superficial neuromasts on the surface of the skin (arrowheads). Scale bar=1 mm.

Fig. S2. Main trunk line neuromasts are arranged in a single line in unplated regions and in dorsal-ventral pairs in plated regions of the flank. Lateral view of a DASPEI-stained threespine stickleback exhibiting the low-plated phenotype. Dotted line indicates the division between the main trunk line anterior (Ma) and main trunk line posterior (Mp) lines. Note that the Ma line contains pairs or groups of neuromasts on lateral plates (plates are not visible in this preparation) whereas the Mp line contains a single row of neuromasts. Scale bar=4 mm.