melanismi

Melanismi, commonly referred to as melanism in English, is the increased development of dark pigmentation in an organism or a body part, resulting from higher melanin production. It can affect skin, fur, scales, or feathers and occurs across many animal groups, including mammals, birds, reptiles, and insects. Melanism is distinct from albinism and leucism, conditions characterized by reduced or altered pigment.

Genetic and environmental factors: In many species, melanism arises from mutations in genes that regulate melanin synthesis and distribution, such as MC1R, ASIP, TYR, TYRP1, and DCT. These mutations can elevate eumelanin production, leading to a predominantly black or dark phenotype. Some cases involve regulatory changes affecting pigment patterning. In some taxa, environmental factors during development can influence pigmentation, but constitutive melanism is typically genetic and heritable.

Ecological and evolutionary aspects: Melanism can affect camouflage, thermoregulation, and signaling, with fitness effects that depend on habitat and predator communities. A well-known example is industrial melanism in the peppered moth (Biston betularia) during the Industrial Revolution in Britain, where darker forms increased in polluted areas, then declined after air quality improved. Melanistic individuals are also common in certain felids (for example, melanistic jaguars and leopards) and in various bird and insect species. The study of melanism informs understanding of natural selection, pigment biochemistry, and adaptation.