Pseudo-melanism, also called abundism, is another variant of pigmentation, characterized by dark spots or enlarged stripes, which cover a large part of the body of the animal, making it appear melanistic. A deficiency in or total absence of melanin pigments is called amelanism.
The morbid deposition of black matter, often of a malignant character causing pigmented tumors, is called melanosis. For a description of melanin-related disorders, see melanin and ocular melanosis.
Melanism related to the process of adaptation is called adaptive. Most commonly, dark individuals become fitter to survive and reproduce in their environment as they are better camouflaged. This makes some species less conspicuous to predators, while others, such as black panthers, use it as a foraging advantage during night hunting. 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 squirrels, many felines and 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.
Industrial melanism is an evolutionary effect in insects such as the peppered moth, Biston betularia in areas subject to 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. Other explanations have been proposed, such as that the melanin pigment enhances function of immune defences, or a thermal advantage from the darker coloration.
Melanistic coat coloration occurs as a common polymorphism in 11 of 37 felid species and reaches high population frequency in some cases but never achieves complete fixation. The black panther, a melanic form of leopard, is common in the equatorial rainforest of Malaya and the tropical rainforest on the slopes of some African mountains, such as Mount Kenya. The serval also has melanic 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. In 1938 and 1940, two melanistic bobcats were trapped alive in sub-tropical Florida.
In 2003, the dominant mode of inheritance of melanism in jaguars was confirmed by performing phenotype-transmission analysis in a 116-individual captive pedigree. Melanistic animals were found to carry at least one copy of a mutant MC1R sequence allele, bearing a 15-base pair inframe deletion. Ten unrelated melanistic jaguars were either homozygous or heterozygous for this allele. A 24-base pair deletion causes the incompletely dominant allele for melanism in the jaguarundi. Sequencing of the agouti signalling peptide in the agouti gene coding region revealed a 2-base pair deletion in black 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.
Melanism in leopards is inherited as a Mendelian, monogenic recessive trait relative to the spotted form. Pairings of black animals have a significantly smaller litter size than other possible pairings. Between January 1996 and March 2009, leopards were photographed at sixteen sites in the Malay Peninsula in a sampling effort of more than 1000 trap nights. Of 445 photographs of melanistic leopards taken, 410 came from study sites 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.
Melanism in leopards has been hypothesized to be causally associated with a selective advantage for ambush. 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 heat.
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.
Melanism, meaning a mutation that results in completely dark skin, does not exist in humans. Melanin is the primary determinant of the degree of skin pigmentation and protects the body from harmful 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 have very dark skin, but this is not melanism.
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 and was promoted by some Afrocentrists, such as Frances Cress Welsing.
Amelanism (also known as amelanosis) is a pigmentation abnormality characterized by the lack of pigments called melanins, commonly associated with a genetic loss of tyrosinase function. Amelanism can affect fish, amphibians, reptiles, birds, and mammals including humans. The appearance of an amelanistic animal depends on the remaining non-melanin pigments. The opposite of amelanism is melanism, a higher percentage of melanin.
A similar condition, albinism, is a hereditary condition characterised in animals by the absence of pigment in the eyes, skin, hair, scales, feathers or cuticle. This results in an all white animal, usually with pink or red eyes.Bernard Kettlewell
Henry Bernard Davis Kettlewell (24 February 1907 – 11 May 1979) was a British geneticist, lepidopterist and medical doctor, who performed research on the influence of industrial melanism on peppered moth (Biston betularia) coloration, showing why moths are darker in polluted areas. This experiment is cited as a classic demonstration of natural selection in action. After live video record of the experiment with Niko Tinbergen, Sewall Wright called the study as "the clearest case in which a conspicuous evolutionary process has actually been observed."Black panther
A black panther is the melanistic color variant of any big cat species. Black panthers in Asia and Africa are leopards (Panthera pardus), and those in the Americas are jaguars (Panthera onca).Charissa obscurata
Charissa obscurata, the annulet or Scotch annulet, is a moth of the family Geometridae. The species was first described by Michael Denis and Ignaz Schiffermüller in 1775. It is found in most of Europe.
It is a variable species, whose ground colour generally reflects the area it inhabits. It is whitish or pale grey in limestone and chalky districts. Darker forms are found in areas with peaty soils. The circular O marks on all four wings are typical but may be vague. The forewings have strongly toothed lines, whose which continue on the hindwings. The margin of the large hindwing is very heavily ruffled and incised, which differ from other species of Charissa moths.The wingspan is 27–32 mm. Adults are on wing from July to August.
The larvae feed on various herbaceous plants, including Calluna species, Viscaria vulgaris, Sedum telephium and Rubus species.E. B. Ford
Edmund Brisco "Henry" Ford (23 April 1901 – 2 January 1988) was a British ecological geneticist. He was a leader among those British biologists who investigated the role of natural selection in nature. As a schoolboy Ford became interested in lepidoptera, the group of insects which includes butterflies and moths. He went on to study the genetics of natural populations, and invented the field of ecological genetics. Ford was awarded the Royal Society's Darwin Medal in 1954.Grey pug
The grey pug (Eupithecia subfuscata) is a moth of the family Geometridae. It is found throughout the Palearctic region and the Near East. It is also found in North America.
The forewings of this species are grey (ccasionally with an ochreous tinge) marked with pale fascia and radial lines which give it a mottled appearance. There is a pale sub-marginal line and a small discal spot. The hindwings are much paler and plainer also with a small black discal spot. Melanism is quite common in this species. The wingspan is 17–21 mm.
The adults fly in May and June with a second brood sometimes emerging in August. The species flies at night and is attracted to light.
The larva feeds on the leaves and flowers of a wide range of plants (see list below). The species overwinters as a pupa.Industrial melanism
Industrial melanism is an evolutionary effect prominent in several arthropods, where dark pigmentation (melanism) has evolved in an environment affected by industrial pollution, including sulphur dioxide gas and dark soot deposits. Sulphur dioxide kills lichens, leaving tree bark bare where in clean areas it is boldly patterned, while soot darkens bark and other surfaces. Darker pigmented individuals have a higher fitness in those areas as their camouflage matches the polluted background better; they are thus favoured by natural selection. This change, extensively studied by Bernard Kettlewell, is a popular teaching example in Darwinian evolution, providing evidence for natural selection. Kettlewell's results have been challenged by zoologists, creationists and the journalist Judith Hooper, but later researchers have upheld Kettlewell's findings.Industrial melanism is widespread in the Lepidoptera (butterflies and moths), involving over 70 species such as Odontopera bidentata (scalloped hazel) and Lymantria monacha (dark arches), but the most studied is the evolution of the peppered moth, Biston betularia. It is also seen in a beetle, Adalia bipunctata (two-spot ladybird), where camouflage is not involved as the insect has conspicuous warning coloration, and in the seasnake Emydocephalus annulatus where the melanism may help in excretion of trace elements through sloughing of the skin. The rapid decline of melanism that has accompanied the reduction of pollution, in effect a natural experiment, makes natural selection for camouflage "the only credible explanation".Other explanations for the observed correlation with industrial pollution have been proposed, including strengthening the immune system in a polluted environment, absorbing heat more rapidly when sunlight is reduced by air pollution, and the ability to excrete trace elements into melanic scales and feathers.J. W. Tutt
James William Tutt (26 April 1858–10 January 1911) was an English schoolteacher and entomologist. He founded and edited the journal Entomologists' Record in 1890 and published a landmark series of volumes on the British Lepidoptera in which he described numerous species of moths. He was among the first to notice industrial melanism, and the melanistic form of the pepper moth Biston betularia which he explained based on the theories of contemporaries as becoming commoner due to industrialism and the role of crypsis in natural selection.
Tutt was born in Strood, Kent and went to the St. Nicholas Schools before going to St. Mark's Training College, Chelsea in 1876. He matriculated in the University of London and became a headmaster at Snowfields Board School followed by Webb Street School and Higher Grade School in Portman Place. Tutt was interested in insects from the age of thirteen but became more scientific after meeting a certain Mr Coverdale in 1881. Tutt was active in London scientific societies including the Entomological Society of London which he joined in 1885. A major contribution was his explanation of melanism that he noted in several insects including the famed pepper moth. He noted this in Yorkshire and provided a selectionist (based on Darwinian natural selection) explanation synthesized from ideas proposed by contemporaries including Buchanan White and Nicholas Cooke.Tutt had a congenital heart condition but lived without much trouble. He died at his home in Rayleigh Villa, Westcombe Hill. He was buried at Lewisham Cemetery. Tutt had been married Frances Marsh Collins and they had two sons and three daughters.Tutt was the author of The British Noctuae and their Varieties (1891–92), Natural History of the British Lepidoptera (1890–1911), Practical hints for the Field lepidopterist (1901) and A natural history of the British Lepidoptera. A text-book for students and collectors (1908).Kettlewell's experiment
Kettlewell's experiment was a biological experiment in the mid-1950s to study the evolutionary mechanism of industrial melanism in the peppered moth (Biston betularia). It was executed by Bernard Kettlewell, working as a research fellow in the Department of Zoology, University of Oxford. He was investigating the cause of the appearance of dark-coloured moth since Industrial Revolution in England in the 19th century. He conducted his first experiment in 1953 in the polluted woodland of Birmingham, and his second experiment in 1955 in Birmingham as well as in the clean woods of Dorset.
The experiment found that birds selectively prey on peppered moths depending on their body colour in relation to their environmental background. Thus, the evolution of a dark-coloured body provided a survival advantage in a polluted locality. The study concluded that "industrial melanism in moths is the most striking evolutionary phenomenon ever actually witnessed in any organism, animal or plant." It is now regarded as the classic demonstration of Charles Darwin's natural selection in action and one of the most beautiful experiments in evolutionary biology.Melanosis
Melanosis is a form of hyperpigmentation associated with increased melanin.It can also refer to:
Riehl melanosisNatural experiment
A natural experiment is an empirical study in which individuals (or clusters of individuals) are exposed to the experimental and control conditions that are determined by nature or by other factors outside the control of the investigators. The process governing the exposures arguably resembles random assignment. Thus, natural experiments are observational studies and are not controlled in the traditional sense of a randomized experiment. Natural experiments are most useful when there has been a clearly defined exposure involving a well defined subpopulation (and the absence of exposure in a similar subpopulation) such that changes in outcomes may be plausibly attributed to the exposure. In this sense, the difference between a natural experiment and a non-experimental observational study is that the former includes a comparison of conditions that pave the way for causal inference, but the latter does not.
Natural experiments are employed as study designs when controlled experimentation is extremely difficult to implement or unethical, such as in several research areas addressed by epidemiology (like evaluating the health impact of varying degrees of exposure to ionizing radiation in people living near Hiroshima at the time of the atomic blast) and economics (like estimating the economic return on amount of schooling in US adults).Pale November moth
The pale November moth (Epirrita christyi) is a moth of the family Geometridae. It is a fairly common species in Western Europe including the British Isles.
This species is almost identical to its relatives the November moth and autumnal moth and it is almost impossible to identify them without examination of the genitalia. In general, although melanism occurs regularly in this species it is less prevalent than in the November moth. The pale November moth flies at night from September to November  and is attracted to light.
The larva feeds on a variety of trees and shrubs (see list below). The species overwinters as an egg.
^ The flight season refers to the British Isles. This may vary in other parts of the range.Paradarisa consonaria
Paradarisa consonaria, the brindled square spot or square spot, is a moth of the family Geometridae. It is found in north and central Europe and east to south-eastern Siberia and Japan.
It is a variable species and has a tendency to melanism. Well-marked individuals have a dark square spot on the forewing. It differs from the crepuscularia group in its tone of colour as well as in the shape and position of the postmedian line. The female is much more whitish than the male and shows a stronger, darker quadrate spot between the postmedian and subterminal lines of the forewing. Abnormal form nigra Bankes is unicolorous blackish except a very small patch of white distally to the cell.The wingspan is 40–45 mm. Adults are on wing from April to June.
The eggs are longitudinally ribbed, and yellow, marked with orange red. Larva elongate, transversely wrinkled, with two minute warts on the 8th abdominal segment: yellowish brown clouded with grey and with reddish. The larvae feed on various deciduous and coniferous trees. On birch, beech, oak, etc. The pupa hibernates.Peppered moth
The peppered moth (Biston betularia) is a temperate species of night-flying moth. Peppered moth evolution is an example of population genetics and natural selection.Peppered moth evolution
The evolution of the peppered moth is an evolutionary instance of directional colour change in the moth population as a consequence of air pollution during the Industrial Revolution. The frequency of dark-coloured moths increased at that time, an example of industrial melanism. Later, when pollution was reduced, the light-coloured form again predominated. Industrial melanism in the peppered moth was an early test of Charles Darwin's natural selection in action, and remains as a classic example in the teaching of evolution. Sewall Wright described it as "the clearest case in which a conspicuous evolutionary process has actually been observed."The dark-coloured or melanic form of the peppered moth (var. carbonaria) was not known before 1811. After field collection in 1848 from Manchester, an industrial city in England, the frequency of the variety was found to have increased drastically. By the end of the 19th century it almost completely outnumbered the original light-coloured type (var. typica), with a record of 98% in 1895. The evolutionary importance of the moth was only speculated upon during Darwin's lifetime. It was 14 years after Darwin's death, in 1896, that J.W. Tutt presented it as a case of natural selection. Due to this, the idea widely spread, and more people believed in Darwin's theory.
Bernard Kettlewell was the first to investigate the evolutionary mechanism behind peppered moth adaptation, between 1953 and 1956. He found that a light-coloured body was an effective camouflage in a clean environment, such as in Dorset, while the dark colour was beneficial in a polluted environment like in Birmingham. This selective survival was due to birds which easily caught dark moths on clean trees, and white moths on trees darkened with soot. The story, supported by Kettlewell's experiment, became the canonical example of Darwinian evolution and evidence for natural selection used in standard textbooks.However, failure to replicate the experiment and criticism of Kettlewell's methods by Theodore David Sargent in the late 1960s led to general skepticism. When Judith Hooper's Of Moths and Men was published in 2002, Kettlewell's story was more sternly attacked, accused of fraud, and became widely disregarded. The criticism became a major argument for creationists. Michael Majerus was the principal defender. His seven-year experiment beginning in 2001, the most elaborate of its kind in population biology, the results of which were published posthumously in 2012, vindicated Kettlewell's work in great detail. This restored peppered moth evolution as "the most direct evidence", and "one of the clearest and most easily understood examples of Darwinian evolution in action".Rock pocket mouse
The rock pocket mouse (Chaetodipus intermedius) is one of 19 species of pocket mice in the genus Chaetodipus. (It is sometimes grouped in the genus Perognathus.)
Found mainly in rocky outcrops in the deserts of the southwestern United States and Mexico, the rock pocket mouse is medium-sized (length ~18 cm, weight ~12–18g) and nocturnal. It eats mainly plant seeds and makes small burrows in soil close to or under rocks to evade owls, its main predator. The breeding season spans a few months, starting in February or March, and the litter size is typically between three and six. As with most pocket mice, the tail is longer than the body (~10 cm).
Historically, rock pocket mice have been subdivided into as many as ten subspecies (Benson 1933; Dice and Blossom 1937) based on geographical distribution and coat colour. Most rock pocket mouse populations have light, tawny fur consistent with the colour of the desert rocks on which they live. However, darker coloured rock pocket mice are found living amid black, basaltic rock formations.
In 2003, scientists sampled DNA from both light- and dark-coloured rock pocket mice from areas in Pinacate Peaks, Mexico and New Mexico, USA. In the Pinacate mice, they discovered a perfect association between different versions of the Melanocortin-1 receptor (Mc41r6) gene and coat colour . Subsequent studies demonstrated that there is strong selective pressure maintaining Mc1r allele and coat colour frequencies across the short geographic distances between the light- and dark-coloured rock islands.Thus melanism in rock pocket mice is considered a fabulous example of adaptation by natural selection. Changes in the Mc1r gene sequence are not responsible for the colour difference in the mice sampled from New Mexico, however, leading the researchers to conclude that the almost identical dark coat colours developed multiple times in rock pocket mice, an example of convergent evolution.The Evolution of Melanism
The Evolution of Melanism: a study of recurring necessity; with special reference to industrial melanism in the Lepidoptera is a 1973 science book by the lepidopterist Bernard Kettlewell.
The book includes Kettlewell's original papers in the journal Heredity on his classic predation experiments on the peppered moth. It also covers Kettlewell's experiments in the Hebrides.White panther
A white panther is a white specimen of any of several species of larger cat. "Panther" is used in some parts of North America to mean the cougar (Puma concolor), in South America to mean the jaguar (Panthera onca) and elsewhere it refers to the leopard (Panthera pardus). A white panther may therefore be a white cougar, a white jaguar or a white leopard. Of these, white leopards appear to be the most common, although still very rare.