DNA methylation of the endothelin receptor B makes blue fish yellow.

Animal pigmentation is essential for concealment and communication in nature. Though selection acts on the phenotypes of an organism, these traits are often resolved to genes that shape pigmentation in populations. In contrast, plasticity in coloration can occur within individuals in response to ambient environmental changes that act through integrative processes. It is well known that some animals often change color to match their visual ecology. The cichlid fish, Astatotilapia burtoni, can switch between robust blue and yellow body morphs in the lab and the wild. Different colors result from the positioning and density of chromatophores between different morphs and patterns. We show that A. burtoni switches from yellow to blue depending on its visual environment by downregulating endothelin receptor B (EdnRBa) mRNA via DNA hypermethylation at a single cytosine residue within its promoter. EdnRBa functions in yellow chromatophores to signal the aggregation of yellow pigments, making yellow less visible. Taken together, the regulation of EdnRBa through DNA methylation in yellow chromatophores contributes to pigmentation changes from blue to yellow morphs and their overall phenotypic plasticity.