leucism

Leucism is a congenital condition characterized by reduced pigmentation in an animal's skin, hair, feathers, or scales, resulting in white or pale coloration in affected areas. Unlike albinism, which is a global absence of melanin affecting skin, hair, and eyes, leucism typically leaves eye coloration and other pigment-free tissues unaffected. It also differs from vitiligo, an autoimmune depigmentation that produces irregular patches in already pigmented areas.

Causes and development: Leucism results from disruptions in the development or function of pigment cells (melanocytes) derived from neural crest cells. Pigment cells may fail to migrate, proliferate, or produce melanin. The condition can be inherited through various genetic mechanisms or arise sporadically as a de novo mutation or developmental error. The pattern and extent of pigment loss vary among species and individuals.

Occurrence and examples: Leucism has been reported across many taxa, including birds, reptiles, mammals, and fishes. Individuals may be completely white or show localized patches of reduced pigmentation. Eye color is generally normal in leucistic animals, though exceptions occur.

Ecological and practical implications: The white or pale appearance can affect camouflage and thermoregulation, influencing behavior and survival in the wild. In captivity or breeding programs, leucistic individuals may be valued for aesthetic reasons, while in the wild they may face different predation risks. Leucism is typically discussed as a natural variation in pigmentation, rather than as a disease.