Fig. 4. Defects in visual axon targeting in regenerating planarians and in phototactic behavior after Smed-netR RNAi. (A) Confocal projections showing the visual axons (VC-1 staining, magenta) relative to the cephalic ganglia (anti-phospho-tyrosine staining, green). In control animals, the visual axons target the brain visual center (arrowheads, n=45/50; 5/50 show minor defects in the visual pattern different from those described below). In Smed-netR dsRNA-injected animals the visual axons do not project posteriorly to the brain visual center (white arrowheads). A black arrowhead in the upper right panel labels an ectopic anterior projection along the midline. All the samples are 2-week regenerants. Anterior to the left. (B) Phototaxis assays. Twenty-five days after Smed-netR RNAi, the negative response to light is significantly slower compared with control and Smed-semcap1 RNAi animals (bottom right panel; *P<0.005; ns, non significant). After Smed-semcap1 RNAi, the anterior commissure is thinner compared with controls and Smed-netR dsRNA-treated animals (white arrows). White arrowheads point to the posterior end of the visual axons, which project more posteriorly after Smed-semcap1 RNAi. Asterisks indicate the position of the eye-cups. Anterior to the top. Scale bar for A: 100 µm. oc, optic chiasm.