Melanism

Source: Wikipedia, the free encyclopedia.
eastern grey squirrel
(Sciurus carolinensis)
Melanistic guinea pigs (Cavia porcellus) are rare, and are used in rituals by Andean curanderos.[1]

Melanism is the congenital excess of melanin in an organism resulting in dark pigment.

Pseudomelanism, also called abundism, is another variant of pigmentation, identifiable by dark spots or enlarged stripes, which cover a large part of the body of the animal, making it appear melanistic.[2]

The morbid deposition of black matter, often of a malignant character causing pigmented

tumors, is called melanosis.[3]

Adaptation

European adder
(Vipera berus) compared to a normal-colored adder

Melanism related to the process of

leopards, use it as a foraging advantage during night hunting.[4] Typically, adaptive melanism is heritable: A dominant allele, which is entirely or nearly entirely expressed in the phenotype
, is responsible for the excessive amount of melanin.

Adaptive melanism has been shown to occur in a variety of animals, including mammals such as

canids, and coral snakes. Adaptive melanism can lead to the creation of morphs, the most notable example being the peppered moth, whose evolutionary history in the United Kingdom is offered as a classic instructional tool for teaching the principles of natural selection.[5]

Industrial melanism

Main article: Industrial melanism

Industrial melanism is an

industrial pollution. Darker pigmented individuals are favored by natural selection, apparently because they are better camouflaged against polluted backgrounds. When pollution was later reduced, lighter forms regained the advantage and melanism became less frequent.[6][7][8][9][10][11] Other explanations have been proposed, such as that the melanin pigment enhances function of immune defences,[12] or a thermal advantage from the darker coloration.[13][14][15]

In cats

See also: Black cat
Melanistic and normally coloured jaguars

Melanistic coat coloration occurs as a common

equatorial rainforest of Malaya and the tropical rainforest on the slopes of some African mountains, such as Mount Kenya. The serval also has melanistic forms in certain areas of East Africa. In the jaguarundi, coloration varies from dark brown and gray to light reddish. Melanic forms of jaguar are common in certain parts of South America.[16] In 1938 and 1940, two melanistic bobcats were trapped alive in sub-tropical Florida.[17]

Pseudomelanism on a cheetah
Melanistic eastern gray squirrel
Melanistic eastern gray squirrel

In 2003, the

domestic cats. These variants were absent in melanistic individuals of Geoffroy's cat, oncilla, pampas cat and Asian golden cat, suggesting that melanism arose independently at least four times in the cat family.[18]

Melanism in leopards is inherited as a

recessive trait relative to the spotted form. Pairings of black animals have a significantly smaller litter size than other possible pairings.[19] Between January 1996 and March 2009, Indochinese leopards were photographed at 16 sites in the Malay Peninsula in a sampling effort of more than 1000 trap nights. Of 445 photographs of melanistic leopards, 410 were taken south of the Kra Isthmus, where the non-melanistic morph was never photographed. These data suggest the near fixation of the dark allele in the region. The expected time to fixation of this recessive allele due to genetic drift alone ranged from about 1,100 years to about 100,000 years.[20]
Melanism in leopards has been hypothesized to be causally associated with a selective advantage for ambush.[21] Other theories are that genes for melanism in felines may provide resistance to viral infections, or a high-altitude adaptation, since black fur absorbs more light for warmth.[22]

In birds

White Silkie rooster
Black Silkie rooster

The chicken breeds Silkie and Ayam Cemani commonly exhibit this trait. Ayam Cemani is an uncommon and relatively modern breed of chicken from Indonesia. They have a dominant gene that causes hyperpigmentation (Fibromelanosis), making the chicken entirely black; including feathers, beak, and internal organs.

In April 2015, an extremely rare black flamingo was spotted on the Mediterranean island of Cyprus.[23]

In amphibians

The alpine salamander, Salamandra atra, has one subspecies (S. atra atra) that is completely black.[24] The pigment comes from a specific cell called a melanophore, which produce the compound melanin.[25][26]

There are four other subspecies of this salamander,[27] and they have varying levels of melanin pigmentation.[26][28][29] The subspecies have yellow spots in different concentrations or proportions. The pigment-producing cells that contribute to the yellow spots of some sub-species are called xanthophores.[28] It appears that the fully-black phenotypes do not ever develop these xanthophores.[29] Alpine salamanders produce a toxin from their skin, and both fully melanistic, black salamanders and spotted individuals produce the compound.[30]

Studies done that traced DNA histories have suggested that the original alpine salamander phenotype was black with some yellow spots, meaning that the fully black color evolved over time and was thus selected for over many generations.[29]

In humans

Melanism, meaning a mutation that results in completely dark skin, does not exist in humans. In humans, the amount of melanin is determined by three dominant alleles (AABBCC), and white people do not have as many as black people.

ultraviolet radiation. The same ultraviolet radiation is essential for the synthesis of vitamin D in skin, so lighter colored skin – less melanin – is an adaptation related to the prehistoric movement of humans away from equatorial regions, as there is less exposure to sunlight at higher latitudes. People from parts of Africa, South Asia, Southeast Asia
, and Australia may have very dark skin, but this is not melanism.

Peutz–Jeghers syndrome

Main article: Peutz–Jeghers syndrome

This rare

macules with hyperpigmentation on the lips and oral mucosa (melanosis), as well as benign polyps in the gastrointestinal tract.[32]

Socio-politics

Further information: Melanin theory

The term melanism has been used on Usenet, internet forums and blogs to mean an African-American social movement holding that dark-skinned humans are the original people from which those of other skin color originate. The term melanism has been used in this context as early as the mid-1990s[33] and was promoted by some Afrocentrists, such as Frances Cress Welsing.

See also

References

  1. ISBN 0-8165-1558-1
    .
  2. S2CID 84554567
    .
  3. ^ Webster's Revised Unabridged Dictionary (1913). Melanosis Archived 2013-07-29 at the Wayback Machine. C. & G. Merriam Co. Springfield, Massachusetts. Page 910
  4. ^ King, R.C., Stansfield, W.D., Mulligan, P.K. (2006). A Dictionary of Genetics, 7th ed., Oxford University Press
  5. ISBN 9781405151986
    .
  6. ^ Majerus, M. E. (2009). Industrial melanism in the peppered moth, Biston betularia: an excellent teaching example of Darwinian evolution in action. Evolution: Education and Outreach, 2(1), 63–74.
  7. ^ McIntyre, N. E. (2000). Ecology of urban arthropods: a review and a call to action. Annals of the Entomological Society of America, 93(4), 825–835.
  8. ^ Cook, L. M., Saccheri, I. J., 2013. The peppered moth and industrial melanism: evolution of a natural selection case study. Journal of Heredity 110:207–12
  9. ^ Grant, B. S., Wiseman L. L., 2002. Recent history of melanism in American peppered moths. Journal of Heredity 93:86-90.
  10. ^ Brakefield, P. M., Liebert, T. G., 2000. Evolutionary dynamics of declining melanism in the peppered moth in the Netherlands. Proceedings of the Royal Society of London Biology 267:1953–1957.
  11. ^ Grant, B. S., Cook, A. D., Clarke, C. A., & Owen, D. F. (1998). Geographic and temporal variation in the incidence of melanism in peppered moth populations in America and Britain. Journal of Heredity, 89(5), 465–471.
  12. ^ Mikkola, K., & Rantala, M. J. (2010). Immune defence, a possible nonvisual selective factor behind the industrial melanism of moths (Lepidoptera). Biological Journal of the Linnean Society, 99(4), 831–838.
  13. ^ Mikkola, K., Albrecht, A., 1988. The melanism of Adalia-bipunctata around the Gulf of Finland as an industrial phenomenon (Coleoptera, Coccinellidae). Annales Zoologici Fennici 25:177–85.
  14. ^ Muggleton, J., Lonsdale, D., Benham, B. R., 1975. Melanism in Adalia-bipunctata L (ColCoccinellidae) and its relationship to atmospheric pollution. Journal of Applied Ecology 2:451–464.
  15. ^ De Jong, P. W., Verhoog, M. D., Brakefield, P. M., 1992. Sperm competition and melanic polymorphism in the 2-spot ladybird, Adalla bipunctata (Coleoptera, Coccinellidae). Journal of Heredity 70:172–178.
  16. ^ Searle, A. G. (1968) Comparative Genetics of Coat Colour in Mammals. Logos Press, London
  17. ^ Ulmer, F. A. (1941) Melanism in the Felidae, with special reference to the Genus Lynx. Journal of Mammalogy 22 (3): 285–288.
  18. S2CID 19021807
    .
  19. S2CID 5446868
    .
  20. doi:10.1111/j.1469-7998.2010.00731.x
    .
  21. ^ Majerus, M. E. N. (1998). Melanism: evolution in action. Oxford University Press, New York
  22. ^ Seidensticker, J., Lumpkin, S. (2006). Smithsonian Q & A: the ultimate question and answer book. Cats. Collins, New York
  23. ^ Krol, Charlotte (2015-04-09). "Rare black flamingo spotted in Cyprus". The Telegraph. Archived from the original on 2015-04-25. Retrieved 2015-05-16.
  24. ^ "Salamandre noire". www.karch.ch. Retrieved 2022-11-30.
  25. PMID 1816547
    .
  26. ^
    PMID 2385569
    .
  27. S2CID 22175429
    .
  28. ^
    S2CID 212664862
    .
  29. ^
    S2CID 83504324
    .
  30. S2CID 235611059
    .
  31. ^ Scheneider, Patricia (2004). "the genetics and evolution of human color". ProQuest.
  32. PMID 30283795
    .
  33. ^ "Sundiata, AFROCENTRISM: THE ARGUMENT WE'RE REALLY HAVING". Retrieved 2007-06-23.

Bibliography

Wikimedia Commons has media related to Melanism.
Retrieved from "https://en.wikipedia.org/w/index.php?title=Melanism&oldid=1217637852"