Neuroendocrine control of physiological color change in Chameleo gracilis

Color changes in Chameleo gracilis are under neuroendocrine control. Denervation of the limbs, by removal of the sciatic or brachial nerves, does not interfere with the normal color changes in the affected limbs. Denervated skins, placed back onto C. gracilis, show color changes in synchrony with the rest of the animal. Pieces of isolated skin turn very dark or black in alpha-melanophore stimulating hormone (alpha-MSH) and green in adrenaline, but do not show any color changes in physiological saline. Hypophysectomized animals turn green but never turn dark. Injections of alpha-MSH cause intact or hypophysectomized animals to turn dark or black, while injections of adrenaline cause them to turn light green. Injections of physiological saline have no effect. Crude pituitary extracts cause darkening of isolated skins or of intact animals injected with such extracts. Similar treatment with crude extracts of adrenal glands causes the skins to become light green. Electrical stimulation of transected spinal cord leads to localized lightening of the skin but never to darkening of the same. Light, temperature, darkness, and color of the surroundings influence color change. Color change to green at night and to darker colors in the daytime suggests a possible circadian rhythm in the phenomenon.