Newly hatched stickleback fry were treated with DMSO (control, A), SB431542 (B–C), XAV939 (D–E), or a combination of the two drugs at low (25µM for SB431542 and 5 µM for XAV939, F) or high (50 µM for SB431542 or 10 µM XAV939, G) doses for 5 days. Main panels show Alizarin red and GFP for the ventral tooth plate; insets show GFP only for mesenchyme of a single tooth from the dorsal tooth plate. (B, C) SB431542 reduced GFP in tooth epithelia (arrows) relative to control (A, and see Fig. 3). However, mesenchymal GFP (arrowhead, inset) was less severely reduced. (D, E) XAV939 alone did not affect GFP expression in epithelia (arrows) or mesenchyme (arrowheads) at either dose. (F, G) No strong additional effect on GFP expression was seen when XAV939 and SB431542 were combined, though mesenchymal GFP appeared slightly lower in the combined dose. (H) A combination of SB431542 and XAV939 significantly reduced ventral pharyngeal tooth number. (I) Treatment with SB431542, but not XAV939, decreased the number of green tooth epithelia relative to total ventral teeth (ratio is expressed as a decimal). XAV939 had no additional effect on green epithelia in combination with SB431542. Tukey HSD P-values of relevant comparisons are shown above with asterisks (*=P<0.05, ** =P<0.0005, n.s.=P>0.05). Scale bars = 200 µm