Guide RNAs (SI Appendix, Fig. S4) were generated as described previously (28 (link)). The plasmids pT7-gRNA and pT3TS-nCas9n were obtained from Addgene (nos. 46759 and 46757). The oligonucleotide sets designed for guide RNAs were as follows: 5′-TAGGGTGGCGGTGTCCTGGGTC-3′ and 5′-AAACGACCCAGGACACCGCCAC-3′ for zebrafish parapinopsin guide RNA and 5′-GGCGTATGAGCGCTATAACG-3′ and 5′-AAACCGTTATAGCGCTCATACG-3′ for zebrafish parietopsin guide RNA. Annealed oligonucleotide sets were inserted into pT7-gRNA, which had been linearized by BsmB I. Guide RNAs were transcribed by using the MEGAscript T7 Transcription Kit. Cas9 mRNA was transcribed in vitro by using the mMESSAGE mMACHINE T3 Transcription Kit (Ambion). Guide RNA (∼50 pg) and Cas9 mRNA (∼150 pg) were coinjected into embryos during the one-cell stage. Mutations in the zebrafish parapinopsin and parietopsin nucleotide sequences were confirmed by a heteroduplex mobility assay (29 (link)). Stop codons appear after Val224 and Ser135 in the PP−/− and PT−/− mutants, respectively. Opsin(s)-deficient fish were obtained by mating the established KO strains.