Dense iridophores (white) cluster in the skin of zebrafish larvae (top left). In juvenile zebrafish, the different pigment cells begin to form stripes, during which immature xanthophores (yellow) extend airinemes to immature melanophores (gray). In adult zebrafish, mature xanthophores (orange) and iridophores form the pale interstripe regions, while mature melanophores (black) form the dark stripe regions. If airinemes are absent, some of the melanophores remain in the interstripe regions (bottom left, Eom et al., 2015). In zebras, epidermal cells (gray) and melanocytes (black) are uniformly distributed, and assignment of stripe identity may depend on periodic changes in the concentration of a Turing-like molecule outside the cells (dotted line) as the skin develops in the fetus. In adult zebra skin, work in horses and other equine animals (Imsland et al., 2015) suggests that hair follicle melanocytes are lost from white stripes.