White or pigmentless or both?
I was fascinated as a kid by Hermann Melville’s story about “Moby Dick”, the white sperm whale chased fanatically by Captain Ahab, but who eventually lost the struggle to kill the beast that had dominated his life and caused him never-ending sleepless nights.
Moby Dick was white: a whale without body pigment. But whether it was a “true” albino and not just an individual lacking body colour is left open in that brilliant novel of Melville’s. White individuals amongst normally coloured ones have been reported from virtually all species and are often prematurely referred to as albinos. However, a true albino not only lacks all coloration in its fur, hair, feathers, scale or, generally speaking, its integument, it also possesses no pigment in its eyes, which therefore appear reddish. Since there is no protection against bright light, the eyes of albinos are often half closed and individuals with such eyes suffer badly from exposures to bright radiation and avoid bright light. Amongst reindeer white specimens become conspicuous during the summer season, but not being true albinos and tolerating bright lights well, one ought to expect them to have an evolutionary advantage in winter when predators like wolves should find it harder to spot them.
True albinos (and not only animals with white bodies) have also been reported from many different animal species, including birds and fish. I remember that in my school there was an albino boy, who constantly wore dark glasses and usually hung around the shady entrance to the school during playtime at school breaks. There are countries and societies where being an albino person can be outright dangerous as a lot of superstition is attached to especially human albinism. For certain animals, it’s a different story and white or albino lions and tigers are usually celebrated as very special individuals. But how common is true albinism as a condition that inhibits the synthesis of body pigments from specific amino acids via one specific recessive gene?
Using the famous Hardy-Weinberg equilibrium equation, an example found in most textbooks of human genetics shows that in a large human population, (given random mating, no mutations and no natural selection) about 1.4 % of the people, which is roughly one person amongst 70, carries the gene for albinism. This figure for humans does not, of course, apply to other species or even specific cases of human populations like those on small islands like Iwa or those in which there is a disadvantage for albinos in the society. However, white individuals and true albinos irrespective of the species they occur in, are just as capable physically and mentally as others – perhaps even more so, because being substantially different in appearance makes them stand out, more vulnerable, more at risk. And to overcome such handicap, they need to be extra smart or tough or both. One wonders whether Zahavi’s idea that females preferentially select handicapped males as partners (as they can be assumed to carry superior genes having made them survive into adulthood and sexual maturity) is applicable to albinos and not just to the peacock with its cumbersome and gaudy feathers or the stag with its heavy and unwieldy antlers. Specimens lacking body colour (and often eyes as well) have -as I had pointed out in another essay- an advantage in a cave environment: there is no need to produce pigments to protect them against radiation or to be seen by a mate or to blend into the background. Where there’s no light, eyes and coloration are luxuries not needed.
The opposite to albinism is melanism, i.e. a black coloration instead of the normal one. Perhaps less common than albinism, it too has been reported from numerous species of all vertebrate orders. I once cared for a beautiful pitch-black melanistic grass snake Natrix natrix. Other famously melanistic examples include the black panther, black squirrel and black wolf. It just occurs to me: what might happen if a black panther produces offspring with an albino panther. Any suggestions?
© Dr V.B. Meyer-Rochow and http://www.bioforthebiobuff.wordpress.com, 2019.
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