Melanism
Videos
Melanism is a congenital high level of melanin in an organism resulting in dark pigmentation.
Black serval (Leptailurus serval)
Black eastern grey squirrel (Sciurus carolinensis)
Melanistic guinea pigs (Cavia porcellus) are rare, and are used in rituals by Andean curanderos.
A melanistic European adder (Vipera berus) compared to a normal-colored adder
Leucism
Videos
Leucism or leukism, is a wide variety of conditions that result in partial loss of pigmentation in an animal—causing white, pale, or patchy coloration of the skin, hair, feathers, scales, or cuticles,
Melanism
…Heterochromia iridum Leucism, a partial loss of pigmentation that results in animals with pale or white skin, hair and/or feathers Melanosis, hyperpigmentation via increased melanin…
Leucistic white lions owe their colouring to a recessive allele. Note the eyes and lips remain the normal colour. Studies have shown that the reduced pigment comes from a mutation in the gene for tyrosinase, the same as causes Type I oculocutaneous albinism in humans.
This white horse owes its coloring to a dominant allele (dominant white).
A leucistic rock dove. Both the eyes and legs are still of the normal colour.
A leucistic house sparrow (Passer domesticus) in Kaycee, Wyoming, USA