This hormone adapts the animal to light backgrounds by stimulating concentration of the pigment of its red body-chromatophores. Strongly expressed in the eyestalk and weakly in brain. Not expressed in other tissues tested. Expression changes during the molting cycle with highest expression in the late pre-molt and post-molt stages, intermediate expression in the intermolt stage and lowest expression in the early pre-molt stage. Temporarily up-regulated under high salt conditions. Belongs to the AKH/HRTH/RPCH family.