The pigment-dispersing hormone causes the migration of the distal retinal pigment into the proximal end of the pigment chromatophore cells and thus decreases the amount of light entering the retinulas. May also function as a neurotransmitter and/or neuromodulator (By similarity). Eyestalk. The function of PDH precursor-related peptide is unknown. The sequence is not well-conserved among different species and that might be an indication that it is inactive. Belongs to the arthropod PDH family. Extended N-terminus.