Melanism
Melanism is the congenital excess of melanin in an organism resulting in dark pigment.
Pseudomelanism, also called abundism, is another variant of pigmentation, identifiable by dark spots or enlarged stripes, which cover a large part of the body of the animal, making it appear melanistic.[2]
The morbid deposition of black matter, often of a malignant character causing pigmented tumors, is called melanosis.[3]
In amphibians[edit]
The alpine salamander, Salamandra atra, has one subspecies (S. atra atra) that is completely black.[24] The pigment comes from a specific cell called a melanophore, which produce the compound melanin.[25][26]
There are four other subspecies of this salamander,[27] and they have varying levels of melanin pigmentation.[26][28][29] The subspecies have yellow spots in different concentrations or proportions. The pigment-producing cells that contribute to the yellow spots of some sub-species are called xanthophores.[28] It appears that the fully-black phenotypes do not ever develop these xanthophores.[29] Alpine salamanders produce a toxin from their skin, and both fully melanistic, black salamanders and spotted individuals produce the compound.[30]
Studies done that traced DNA histories have suggested that the original alpine salamander phenotype was black with some yellow spots, meaning that the fully black color evolved over time and was thus selected for over many generations.[29]