|[Note Guidelines] Photographer's Note|
|Blackbuck (Antilope cervicapra) is a species of antelope found mainly in India, and also in some parts of Pakistan and Nepal. There are also introduced populations in various parts of the world including numerous ranches in Texas in the United States of America; free-ranging populations also exist in Argentina and in southern Australia.|
The distinctive horns of the Blackbuck are ringed with 1 to 4 spiral turns, rarely more than 4 turns, and can be as long as 79 cm (31 in). A trophy Blackbuck is greater than 46 cm (18 in). The white blackbuck on the extreme right has 5 spiral turns.
Albinism in Blackbucks is rare and caused by the lack of 'Melanin'. The animal looks fully white due to the lack of melanin in their skin. Wildlife experts say that the biggest problem with these Albinos is that they are singled out by predators and hunted. These are Albinos.
Leucism is a condition characterized by reduced pigmentation in animals and humans. Unlike albinism, it is caused by a reduction in all types of skin pigment, not just melanin. Example:Leucistic Texas Rat Snake, Leucistic Indian Peafowl, White lions, Leucistic Chipping sparrow (Spizella passerina).
Leucism (also spelled Leukism) is a general term for the phenotype resulting from defects in pigment cell differentiation and/or migration from the neural crest to skin, hair or feathers during development. This results in either the entire surface (if all pigment cells fail to develop) or patches of body surface (if only a subset are defective) having a lack of cells capable of making pigment.
Since all pigment cell-types differentiate from the same multipotent precursor cell-type, leucism can cause the reduction in all types of pigment. This is in contrast to albinism, for which leucism is often mistaken. Albinism results in the reduction of melanin production only, though the melanocyte (or melanophore) is still present. Thus in species that have other pigment cell-types, for example xanthophores, albinos are not entirely white, but instead display a pale yellow colour.
More common than a complete absence of pigment cells is localized or incomplete hypopigmentation, resulting in irregular patches of white on an animal that otherwise has normal colouring and patterning. This partial leucism is known as a "pied" or "piebald" effect; and the ratio of white to normal-coloured skin can vary considerably not only between generations, but between different offspring from the same parents, and even between members of the same litter. This is notable in horses, cows, cats, dogs, the urban crow and the ball python but is also found in many other species.
A further difference between albinism and leucism is in eye colour. Due to the lack of melanin production in both the retinal pigmented epithelium (RPE) and iris, albinos typically have red eyes due to the underlying blood vessels showing through. In contrast, leucistic animals have normally coloured eyes. This is because the melanocytes of the RPE are not derived from the neural crest, instead an outpouching of the neural tube generates the optic cup which, in turn, forms the retina. As these cells are from an independent developmental origin, they are typically unaffected by the genetic cause of leucism.
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