File talk:White bison by N A Nazeer.jpg

Leucism?

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Hi Richard, Could you explain a bit more why you remove this from Albinism?. I didn't understand what you mean by "this animal is clearly leucistic". JKadavoor Jee 02:46, 30 November 2013 (UTC) Please have a look at Leucism. An albino animal has no melanin (black or brown pigment) at all, so it is pure white, or it may have some orange or yellow from other pigments such as carotenoids (this is discussed in Albinism#In animals). It will have pink eyes. The gaur in the photo is also shown in this photo: File:White_bison_by_N.A._Naseer.jpg (both photos are used in "Albino" gaur). It clearly shows the usual gaur pigmentation pattern, but in paler form. For example, it has the typical gaur white socks, which contrast with the brownish colour of the upper legs. In a true albino the socks would not be distinguishable, because the whole body would be the same white. The colour of this animal is clearly the brown of melanin, not the yellow of carotenoids or other non-melanin pigments. This sort of colour dilution is familiar in domestic animals, and in wild animal populations it's often an indication of some domestic ancestry. I do wonder if there is a history of keeping mithun in the area where these pale gaur are found. Even pure white animals often turn out to be leucistic rather than albino – close examination shows pigment in the iris and skin, or small flecks of pigment in the fur. This applies for example to white domestic sheep and chickens, and to the white fallow deer we often get here in the New Forest. It can make it difficult to tell a true albino from a leucistic animal – but in the case of this gaur there is no such doubt: it's definitely leucistic. I think the confusion in this case has arisen because of the loose use of the word "white", when what is really meant is "very pale" when compared with normal very dark gaur. Regards, Richard New Forest (talk) 11:21, 30 November 2013 (UTC) Thanks for the detailed reply. Shyamal also gave me the same reply. Do we need to change the file description accordingly? You may add your findings/opinion on the file talk page in Commons. JKadavoor Jee 13:06, 30 November 2013 (UTC)

JKadavoor Jee 14:41, 30 November 2013 (UTC)

Leucism versus albuinism

I know that there is an old idea, that diluted colors belong to leucism and spotted animals is some sort of partial alminism. In fact albinism ist due to defects in the melanin synthese and diluted colors in most cases are too. Leucism is due to defects in the traveling of melanocytes and spotted colors are too. Therefore people who know the details of color genetics know that diluted colors are partisl albinism. Kersti (talk) 07:47, 8 May 2018 (UTC)

[+Jkadavoor, +Shyamal, +Kersti Nebelsiek The above comment is moved from another page.--Praveen:talk 15:46, 8 May 2018 (UTC)]

Albino vs albinistic

Since this has been a contested issue in the past, here is my rationale for re-categorising this to "albinism in mammals":

• "albinism" refers to lowered function of pigment cells--resulting in diluted colouration
• albinistic skin will have pigment cells, but abnormal (deficient) pigment production
• albinism affects the pigment in the entire animal, although some types will dilute one pigment but not others
• "albino" is a special, "complete" case of albinism, usually understood to feature white to cream colouration with pink/red or pale blue/grey eyes in animals whose pigments only consist of melanins
• "leucism" refers to incomplete distribution of pigment cell precursors--resulting in variously white-spotted colouration
• leucistic patterns vary from complete whiteness (with blue or normal eyes) to small distal white markings in face and feet
• leucistic skin will be devoid of pigment cells (and therefore pigments) altogether, with other areas being unaffected
• leucism and albinism can and do co-occur (such as in this single cream dilute, tobiano-spotted pony).

Since the animal in question here is all over affected, features no stark white markings, and features a markedly diluted pigment in comparison to the unaffected specimen, I am moving this file back to Category:Albinism in mammals. --Pitke (talk) 10:39, 23 June 2020 (UTC)