melanophores

Melanophores are pigment-containing cells responsible for the production and distribution of melanin in the skin and other integuments of several vertebrate groups, most notably fish and amphibians. They belong to the broader class of chromatophores, pigment cells that contribute to the animal’s coloration. In contrast to mammalian melanocytes, which reside in the epidermis and are relatively fixed, melanophores in these groups can rapidly alter color by moving melanosomes within the cell.

Structure and mechanism: Melanophores contain melanosomes, organelles that store melanin. Color change is achieved by dispersion or aggregation of melanosomes within the cytoplasm, driven by neural and hormonal signals. In many fish and amphibians, the dispersion of pigment granules darkens the skin, while aggregation lightens it. Hormones such as alpha-melanocyte-stimulating hormone (alpha-MSH) promote dispersion, whereas melatonin tends to induce aggregation. The response can be rapid, occurring within seconds to minutes in some species.

Development and ecology: Melanophores originate from neural crest cells during embryonic development and populate the dermis. They often interact with other chromatophores, such as erythrophores and xanthophores, to form a dermal chromatophore unit that produces a range of colors. The primary ecological roles of melanophores include camouflage, social and mating signaling, and thermoregulation in certain species.

Pathology and variation: Abnormal melanophore function or density can contribute to color disorders and, in some species, to depigmentation or hyperpigmentation patterns. In many animals, melanophore number and distribution shift during growth, affecting coloration.