Nature Note – Fish Chromatophores

Chromatophores on a rock bass change color at night. Photo by Amy Calkins.

Ever wonder what makes brook trout spots so orange? Or sunfish so bright? The color of fish is determined by the arrangement and patterns of chromataphores in their scales. Chromatophores are pigment-containing and light-reflecting organelles within the cells.

Chromatophores color can change with environmental conditions, for example at night. As the light reaching a fish’s eyes changes, signals from a fish's nerves then rearrange the pigments in the chromatophores to make them darker or lighter shifting the color patterns on the scales.