Melanophore

Melanophores

Melanophores contain eumelanin, a type of melanin, that appears black or dark-brown because of its light absorbing qualities. It is packaged in vesicles called melanosomes and distributed throughout the cell. Eumelanin is generated from tyrosine in a series of catalysed chemical reactions. It is a complex chemical containing units of dihydroxyindole and dihydroxyindole-2-carboxylic acid with some pyrrole rings. The key enzyme in melanin synthesis is tyrosinase. When this protein is defective, no melanin can be generated resulting in certain types of albinism. In some amphibian species there are other pigments packaged alongside eumelanin. For example, a novel deep (wine) red-colour pigment was identified in the melanophores of phyllomedusine frogs. Some species of anole lizards, such as the Anolis grahami, use melanocytes in response to certain signals and hormonal changes, and is capable of becoming colors ranging from bright blue, brown, and black. This was subsequently identified as pterorhodin, a pteridine dimer that accumulates around eumelanin core, and it is also present in a variety of tree frog species from Australia and Papua New Guinea. While it is likely that other lesser-studied species have complex melanophore pigments, it is nevertheless true that the majority of melanophores studied to date do contain eumelanin exclusively.