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要旨

The genetic basis of morphological variation provides a major topic in evolutionary biology. The genus Danio displays a striking variation of colour patterns ranging from horizontal stripes, to vertical bars or spots. In zebrafish, Danio rerio, the strict horizontal orientation of the stripes depends upon the horizontal myoseptum as anatomical landmark, otherwise stripe formation is a self-organizing process
based on cell-contact–mediated interactions among three different types of chromatophores. Patterning mutants from D. rerio provide candidate genes that might have evolved to contribute to the differences observed in Danio species. Here, we show that stripe or bar formation differentially depend on the horizontal myoseptum, but self-organization is a common mechanism of pattern formation. Several mutations in the barred sibling species, Danio aesculapii, lead to phenotypes that indicate species-specific differences in the interactions between chromatophores. Using a reciprocal heterozygosity test in interspecific hybrids, we identify an evolved gene, which regulates heterotypic cell interactions in both species but contributes to patterning differences between species. Our results highlight the power of in vivo genetic tests, which are now possible in non-model organisms by CRISPR/Cas9–mediated reverse genetics, to identify loci that
underlie morphological variation of complex traits in vertebrates.