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pigment cell[′pig·mənt ‚sel]
(also called chromatophore), any vertebrate animal or human cell whose cytoplasm contains colored substances that are called pigments, which are responsible for skin color and the color of certain internal organs. The principal types of pigment cells are melanocytes and melanophores, which contain melanin; xanthophores, which contain carotenoids, flavins, and pterins; and iridocytes, or guanophores, which contain guanidine crystals. Melanin ranges in color from yellow to blackish; carotenoids, flavins, and pterins range from yellow to red; and guanidine crystals impart an iridescent silver or gold sheen. By engulfing pigment granules of decomposing pigment cells, macrophages can take on the appearance of pigment cell.
The coloration of fish, amphibians, and reptiles is predicated by the combined pattern of pigment cells of different shapes and sizes in the skin. The coloration of birds and mammals depends mostly on the color of the feathers and hairs, which absorb pigment from pigment cells in the papilla at the base of each feather or hair.
Pigment cells originate in the course of embryonic development from the neural crests, which are situated between the neural plate and the ectoderm. Their coloration and the various markings that they produce depend on several factors. One important factor is the interaction of the developing pigment cells both among each other and with the surrounding tissues, especially the epidermis. In amphibians, many fishes, and certain reptiles—for example, chameleons—pigment granules can either migrate to the outgrowths of the pigment cells or accumulate around the nucleus. This enables the animal to change its color quickly as it adapts to the environment. Adaptive changes in coloration and markings are controlled by the nervous system in response to visual stimuli, by pituitary and thyroid hormones, and by hormones of the pineal body.
REFERENCESProsser, L., and F. Brown. Sravnitel’naia fiziologiia zhivotnykh. Moscow, 1967. Pages 566-600. (Translated from English.)
Bagnara, J. T. “Cytology and Cytophysiology of Nonmelanophore Pigment Cells.” International Review of Cytology, 1966, vol. 20, pp. 173-205.
O. G. STROEVA