Albinism is the congenital absence ofmelanin in an animal or plant resulting in white hair, feathers, scales and skin and red, pink, purple, or blue eyes.[1][2] Individuals with the condition are referred to asalbinos.
Varied use and interpretation of the terms mean that written reports of albinistic animals can be difficult to verify. Albinism can reduce the survivability of an animal; for example, it has been suggested that albino alligators have an average survival span of only 24 years due to the lack of protection from UV radiation and their lack of camouflage to avoid predators.[3] It is a common misconception that all albino animals have characteristic pink or red or violet eyes (resulting from the lack of pigment in theiris allowing the blood vessels of the retina to be visible); this is not the case for some forms of albinism.[4] Familiar albino animals include in-bred strains oflaboratory animals (rats, mice and rabbits), but populations of naturally occurring albino animals exist in the wild, e.g.,Mexican cave tetra. Albinism is a well-recognized phenomenon in molluscs, both in the shell and in the soft parts. By definition albinism is a genetic condition, however a similar coloration could be caused by diet, living conditions, age, disease, or injury.[5]
Oculocutaneous albinism (OCA) is a clearly defined set of seven types of genetic mutations which reduce or completely prevent the synthesis ofeumelanin orpheomelanin, resulting in reduced pigmentation.[6] Type I oculocutaneous albinism (OCA1a) is the form most commonly recognised as 'albino' as this results in a complete absence ofmelanin in the skin, hair/fur/feathers, and pink pupils, however this has led many to assume that all albinos are pure white with pink pupils, which is not the case.[7][8][6]
In plants, albinism is characterised by partial or complete loss ofchlorophyll pigments and incomplete differentiation of chloroplast membranes. Albinism in plants interferes withphotosynthesis, which can reduce survivability.[9] Some plant variations may have white flowers or other parts. However, these plants are not totally devoid of chlorophyll. Terms associated with this phenomenon are "hypochromia" and "albiflora".[10]
Biological pigments are substances produced by living organisms that have a colour resulting from selectivecolour absorption. What is perceived as a plant or animal's "colour" is the wavelengths of light that are not absorbed by the pigment, but instead are reflected. Biological pigments includeplant pigments andflower pigments.
Animals can appear coloured due to two mechanisms, pigments andstructural colours. Animals may have both biological pigments and structural colours, for example, somebutterflies with white wings.
Many animal body-parts, such asskin,eyes,feathers,fur,hair, scales and cuticles, contain pigments in specialized cells calledchromatophores. These cells are found in a wide range of animals includingamphibians,fish,reptiles,crustaceans andcephalopods.Mammals andbirds, in contrast, have a class of cells calledmelanocytes for colouration. The term chromatophore can also refer to coloured, membrane-associated vesicles found in some forms of photosyntheticbacteria. Chromatophores are largely responsible for generating skin and eye colour inpoikilothermic animals and are generated in theneural crest during embryonic development. Mature chromatophores are grouped into subclasses based on their colour under white light:
Animals can also appear coloured due tostructural colour, the result ofcoherent scattering[11] perceived asiridescence. The structures themselves are colourless. Light typically passes through multiple layers and is reflected more than once. The multiple reflections compound one another and intensify the colours. Structural colour differs according to the observer's position whereas pigments appear the same regardless of the angle-of-view. Animals that show iridescence includemother of pearl seashells, fish, and peacocks. These are just a few examples of animals with this quality, but it is most pronounced in the butterfly family.
iridophores (reflective/iridescent): sometimes called "guanophores", reflect light using plates of crystalline chemochromes made fromguanine[12]
leucophores (reflective white): found in some fish, utilize crystallinepurines (often guanine) to produce a reflective, shiny, white colour.
Definitions of albinism vary and are inconsistent. While they are clear and precise for humans and other mammals, this is because the majority of mammals have only one pigment, melanin. Many animals have pigments other than melanin, and some also have structural colours. Some definitions of albinism, whilst taking most taxa into account, ignore others. So, "a person or animal with very pale skin, white hair or fur, and pink eyes caused by a medical condition that they were born with"[13] and "a person or animal with white skin and hair and pink, red and violet eyes"[14] do not include feathers, scales or cuticles of birds, fish and invertebrates, nor do they include plants. Some definitions are too broad to be of much use, e.g. "an animal or plant with a marked deficiency in pigmentation".[15]
Other definitions of albinism encompass most of the major animal taxa, but ignore the several other pigments that non-mammalian animals have and also structural colouration. For example, "Absence of the pigment melanin in the eyes, skin, hair, scales, or feathers."[16] refers only to the pigment melanin.
Because of the various uses of different terms applied to colouration, some authors have indicated that the colour of the eyes is the defining characteristic of albinism, e.g. "This leads to a good diagnostic feature with which to distinguishleucistic and albino individuals – the colour of the eye."[17] However there are several forms of albinism – currently seven types recognised for humans – most of which do not result in red or pink pupils.[4]
The term "partial albino" is sometimes used in the literature. However it has been stated that "A common misnomer is 'partial albino' – this is not possible since albinism affects the whole plumage of a bird, not just part"[17] and the definition of albinism precludes the possibility of "partial albinism" in which a mostly white bird shows some form of melanin pigmentation. "It is simply impossible, just like being 'partially pregnant'".[18] Conditions that are commonly termed "partial albino" includeneural crest disorders such aspiebaldism,Waardenburg syndrome, or other depigmentation conditions such asvitiligo. These conditions result from fundamentally different causes to the seven types ofoculocutaneous albinism that have been identified in humans (and confirmed in some other animals) and the use of the term "partial albino" is therefore misleading.[6]
One definition states that "albinism (from the Latin albus, meaning "white"), hereditary condition characterized by the absence of pigment in the eyes, skin, hair, scales, or feathers",[19] However this does not encompass invertebrates, nor does it include plants. Furthermore, it could be interpreted that "...absence of pigment..." does not include an absence of structural colours.
The lack of clarity about the term is furthered when the name of an animal includes the term "albino" although the animals (clearly) do not have the condition. For example, thealbino gaur has this name because it is ash-grey whereas other gaur are almost black.
A clear definition appears to be – "Congenital absence of any pigmentation or colouration in a person, animal, or plant, resulting in white hair and pink eyes in mammals."[2] Whilst this does not state specifically that non-mammalian albino animals (or plants) are white, this can be inferred from "...absence of any pigmentation or colouration..." Due to the varied use and interpretation of the term "albino", written reports of albinistic organisms can often not be verified.
A hedgehog with albinism due to a genetic mutation
Melanin is an organic pigment that produces most of the colour seen in mammals. Depending on how it is created, melanin comes in two colour ranges,eumelanin (producing dark browns and blacks) andpheomelanin (producing light reddish tans and blondes). The dark and light melanins have their influence either alone or in conjunction, making either plain or multi-coloured coats. Sometimes, in a condition calledagouti, they make multi-coloured individual hairs. The production of melanin occurs inmelanocytes in a complex process involving the enzymetyrosinase. Mammals have a gene that codes for the presence of tyrosinase in cells – called the TYR gene. If this gene is altered or damaged, melanin cannot be reliably produced and the mammal becomes an albino. Besides the TYR gene, several other genes can cause albinism. This is because other hormones and proteins are involved in melanin production, the presence of which is genetically determined. In mice, a total of 100 genes are known to affect albinism.[20]
Most forms of albinism follow a recessive pattern of inheritance.[21] However, this is not always the case. Inpalomino horses, genes coding for coat whiteness are dominant, and this is also true for several arctic mammals who possess dominant white colors which are pseudo-albinistic. However, these mammals differ from truly recessive albinos in that they still producetyrosinase, and have normal eye pigmentation.[22] In Japan, research has identified a dominant albinism in therainbow trout.[23][24]
Albinism occurs throughout the animal kingdom. The condition is most commonly seen in birds, reptiles and amphibians, but more rarely seen in mammals and other taxa. It is often difficult to explain occasional occurrences, especially when only one documented incidence has occurred, such as only one albino gorilla and one albinokoala.[25] In mammals, albinism occurs once in every 10,000 births, but in birds, the rate is once in every 1,764 births.[26]
Some species, such as white peacocks, swans and geese, are not believed to be true albinos, as they do not have red eyes, rather, their colouration is suggested to be the expression of a white fur or feather gene, not a lack of melanin.[27]
Melanin functions in the normal development of various parts of the eye, including the iris, retina, eye muscles, and optic nerve. The absence of melanin results in abnormal development of eyes and leads to problems with focusing, and depth perception. The eyes of albino animals appear red because the colour of thered blood cells in theretina can be seen through the iris, which has no pigment to obscure this. Some albino animals may have pale-blue eyes due to other colour generating processes. Albino vertebrates exposed to intense light typically losephotoreceptors due toapoptosis.[28]
A true albino squirrel. Note the reddish-pink eyes.
In all albino mammals studied, the centre of the retina is under-developed and there is a deficit of rod cells, which detect light levels; the central ganglion cell density is approximately 25% below normal (except for theeastern gray squirrel). In nearly all mammals, the overwhelming majority of photoreceptors are rods rather than cones, which detect color. Albinism specifically affects the rod cells, but the number and distribution of the cones is unaffected. In contrast, the retinas of birds are cone rich, meaning that the vision of albino birds is affected less than albino mammals.[29]
Reduced protection from sunlight in albino creatures
Melanin protects the skin fromultra-violet radiation in sunlight.Melanosomes block harmfulelectromagnetic radiation from the sun while allowing beneficial frequencies to enter the body. This means some animals may die from UV radiation due to a lack of protection. Albino humans must use an excessive amount of sunscreen, even if the sun is hidden behind the clouds.
Animals with albinism may lack protectivecamouflage in some environments, and are therefore less able to conceal themselves from their predators or prey. However, in other environments albino animals are less likely to be killed, and selection may favor them.[30] The lower survival rate of animals with albinism in certain environments has been documented,[31][32] however, it has been stated that in studies where animals had many places to hide, predators captured albino and normally coloured animals at the same rate.[20] Furthermore, in certain species, albino animals may be excluded from families or other groups,[26] or rejected as mates.[20] On the other hand, there is also evidence for positive selection for albinism in some animals,[33] as well as cultural selection favoringalbino people in some human societies, which results in the increase of genes associated with albinism.[34] Thefounder effect may explain why some animal populations become selected for albinism.[35]
They have also been protected in studies on their ecology, sociology and behaviour.[36]
Studies onmedaka fish in the laboratory, i.e. with no predators, sufficient food supply, controlled temperatures, etc., found that albinos had considerably reduced viability; from 800 albino embryos, only 29 survived to full adulthood.[37] Early studies on fish led some researchers to describe albinism as a "semi-lethal mutation".[37]
Examples of pet mammals artificially selected for albinism
Albino ferret
Albino rabbit
Intentionally bred albinistic strains of some animal species are commonly used asmodel organisms in biomedical research and also as pets. Examples include theBALB/c mouse andWistar andSprague Dawley rat strains, laboratory rabbits and ferrets.[39] Some researchers have argued that albino animals are not always the best choice for scientific studies due to the consequences of albinism (e.g. hearing and visual impairments).[40]
Many individual albino mammals are in captivity and were caught while young. However, the survival prospects of these creatures into adulthood outside of captivity are uncertain.[citation needed] It is doubtful whether these individuals would have survived to become adults without the protection and care they receive in captivity.[41]
It has been claimed that "Squirrels are the only known albino mammals to survive successfully in the wild".[29] The retina of the squirrel (Sciurus carolinensis) is unusual for mammals as it is rich in cones. Central cell densities are less than 5% lower in albino squirrels than in pigmented individuals. This relatively minor disruption to vision is thought to assist in the survivability of albino squirrels in the wild. This is supported by observations that the behaviour of albinos in the wild, e.g. leaping from branch to branch, is similar to pigmented squirrels.[29]
Albinism was observed injungle cats (Felis chaus) andjackals (Canis aureus) along the coastline of the southern Western Ghats (Kerala and Kanyakumari coast, India). Albinism was observed in jungle cats from the Amaravila area of Trivandrum district in the Kerala State. Albinism in jackals was observed from the Polooni area in Malappuram district and Chaliyam area of Calicut district (Kerala). As albinism is observed in those areas where the density of these mammals is comparatively low, it is concluded that continuous inbreeding could be the reason for expression of albinism.[43]
A study on albinisticprairie voles (Microtus ochrogaster) found that albinism in this species conferred an advantage for the males compared to the wild-type; albino males had higher mount frequencies than wild-type males. In addition, the albinos had greater differential fertilizing capacity.[44]
The costs of albinism for marine mammals may include reduced heat absorption in colder waters, poor camouflage from predators, increased sensitivity to sunlight, and impaired visual communication. Despite the costs, some individuals do reach adult age and breeding status.[45]
Albino dolphins were first sighted in the Gulf of Mexico in 1962. Since 1994, three further individuals have been seen. These tend to be pink in colour due to blood vessels showing through the blubber and unpigmented skin.
A report published in 2008 stated that in marine mammals, "anomalously white" individuals have been reported for 21 cetacean species and sevenpinniped species but there were no known reports of anomalously whitesea otters (Enhydra lutris) orsirenians.[45]
Whales and dolphins also may appear white if extensively scarred, or covered with a fungus, such asLacazia loboi.[45]
The most important pigments that determine plumage colouration in birds are melanines and carotenoids. The latter are ingested in food and transformed into colour pigments by enzymes. Aberrations in this pigmentation are mostly caused by food deficiencies and usually do not have a genetic basis. Well-known examples areflamingos, which owe their distinct pink colour to the presence of red carotenoids in their natural food. When these carotenoids are in short supply, these birds appear white after the nextmoult. Mutations causing changes in carotenoid-based colour pigments are rare; melanine mutations occur much more frequently. Two types of melanin, eumelanin and phaeomelanin, are present in birds. In the skin and eyes, only eumelanin is present. In some bird species, the colour is completely caused by eumelanin, however, both types of melanin are found in most species. In birds, albinism has been defined as "a total lack of both melanins in feathers, eyes and skin as a result of an inherited absence of tyrosinase",[18] however, this ignores the effects of other pigments and structural colours.
An albino bird has a white beak, white plumage, non-coloured skin, whitetalons and pink or red eyes.Albinism is only seen in about 1 of every 1,800 birds. The two most common species of albino birds are thecommon house martin and theAmerican robin.[25] Famous albino birds include "Snowdrop", aBristol Zoopenguin.[48]
In one study, albinism in birds has been categorised according to the extent of pigment absence.[49]
Total albinism – a simultaneous complete absence of melanin from the eyes, skin, and feathers. This is the rarest form. Only 7% of 1,847 cases of avian albinism examined was this type.
Incomplete albinism – when melanin is not simultaneously absent from the eyes, skin and feathers.
Imperfect albinism – when melanin is reduced in the eyes, skin and feathers.
Partial albinism – when albinism is localized to certain areas of the body.
However, it has been argued that the definition of albinism precludes the possibility of "partial albinism" in which a mostly white bird shows some form of melanin pigmentation. "It is simply impossible, just like being 'partially pregnant'.[18]
Zebrafish have three types of chromatophores—iridophores, melanophores, and xanthophores—which produce silver, black, and yellow pigmentation respectively. Zebrafish that lack iridophores are known asroy mutants, those that lack melanophores asalbino mutants, and those which lack both melanophores and iridophores areruby mutants. The gross eye morphology, feeding and swimming behaviours between wild-type and albino zebrafish were indistinguishable, except under dim or bright light or low contrast.[50]In mammals, albinism is occasionally associated with hearing impairments. However, when tested, there was no differences in responses between wild-type and albinistic European wels catfish (Silurus glanis) and South American bronze catfish (Corydoras aeneus). Similarly, Mexican blind cave fish (Astyanax mexicanus) do not differ in hearing sensitivity from the normally pigmented and eyed surface-dwelling populations. Fish lack melanin in the inner ear, meaning that hearing in fishes is less likely to be affected by albinism than in mammals.[38]
There are several reports of total albinism in both freshwater and marine fish, however, frequently captured albino fish are only reported in aquarium magazines and local newspapers.[51]
The incidence of albinism can be artificially increased in fish by exposing the eggs toheavy metals (e.g. arsenic, cadmium, copper, mercury, selenium, zinc).[52]
In the wild, albinism is reasonably common in theteleosts, especially thePleuronectiformes (flatfish), however, it is rarely reported in theelasmobranchs.[53] Albinism has been reported in hagfish, lampreys, sharks, rays and numerous teleost fishes, e.g. catfishes, grunts or cyprinids.[38]
Albino and normally pigmentedchannel catfish (Ictalurus punctatus) differ in their characteristics. Normal individuals of this species are superior to albinos in body weight and total length. Albinos crossed with other albinos require 11 days longer to spawn and produce smaller egg masses. These masses contain eggs of lighter weight with poorer hatchability than crosses of normal fish. The albino fish have lower survival rates than normal fish but dress-out percentages are nearly equal.[54]
Some wildcave fish have populations that are albinistic. TheMexican cave tetra is a species that has evolved specialized characteristics in a series of independent caves. One of these is albinism linked to theOca2 gene, a known pigmentation gene. This trait has evolved independently in at least two caves.[55]
In the classChondrichthyes, several species of naturally occurring albino rays and sharks have been recorded. Furthermore, an albino individualspotted ratfish (Hydrolagus colliei) from the orderChimaeriformes has been reported.[56]
Albinistic individuals of the following shark species have been reported:[57][58][59]
Many reptiles labeled as albino are, in fact, not completely lacking in all colour pigments. They are actuallyamelanistic, not albino. Reptiles often possess at least two pigments. Among the most common are xanthin (yellow) and erythrin (red). An amelanistic reptile therefore, may still have pale yellow, orange, or red pigmentation.
TheCalifornia Academy of Sciences, in theSteinhart Aquarium, as of 2015, has on display an albino American alligator named "Claude". The alligator is partially blind because of lack of pigment in its eyes.[61] The albino alligator hatched from the egg in 1995 in Florida, and was brought to the academy in 2008. This alligator would not have survived in the wild because its whiteness would have made it too easy a prey object. The only known albino alligators are in captivity.[62] While extremely rare, white-colouredcrocodiles andalligators do exist in other places. However, most of these animals areleucistic given that they have a general loss ofpigmentation with some colour tinges remaining on their bodies although looking at first like other albino creatures, thus creating the misconception that the reptiles are albino themselves when they are not. Four such alligators are kept at theGatorlandtheme park in the U.S. state ofFlorida.[63] In Australia, a crocodile believed to be "part-albino" and nicknamed by people in the area as "Michael Jackson", attacked and killed a man.[64]
In snakes, partial absence of pigment is more common than absolute albinism. For snakes that are usually patterned in colours, they appear as a faint blue, peach or yellowish. In these cases, there has been a genetic mutation in the melanin and pigment delivery. The appearance comes from the inability for full colours to be present, such as black, red, brown and others. The eyes of an albino snake are typically red or pink. Albino snakes can remain in the sunlight for several hours with minimal harm.Corn snakes and snakes of larger types, such as aboa or diamondback snakes, are the most commonly affected by albinism often appearing to be a pinkish or yellowish colour.[25]
Albino tortoises and turtles are uncommon;Sulcata tortoises are the most likely type of turtle to express albinism. The shells have an almost yellow colouration and they have pink eyes. For turtles, a pure white colour is nearly impossible, even with albinism. Albino turtles can have a longer lifespan than many other albino animals; their hard shells help to prevent predation and other environmental challenges. Vision and sensory organs are slightly affected.[25]
In 2012, an albinoanole was reported and photographed.[65] In 2007, it was reported that an albino stumpy-tail lizard (possibly ashingleback lizard), approximately 12 cm (4.7 in) long and roughly 1 year old, had been found in Victoria, Australia.[66]
There are three known "albino" strains ofleopard gecko, however, breeders state that albinos are generally recognized by their lack of black pigment and having red eyes is not a requirement to be considered an albino. These three strains are called "tremper albinos", "rainwater albinos" and "bell albinos".[67]
As with reptiles, many amphibians labeled as albino are, in fact, not completely lacking in all colour pigments. They are actually amelanistic, not albino. Amphibians have six types of chromatophore in their skin, i.e. melanophores, xanthophores, erythrophores, leucophores, cyanophores and iridophores.[68] An amelanistic amphibian therefore, may still have various pigmentation.
The incidence of albinism in frogs, salamanders, and newts is relatively higher than other taxa. It has been estimated that one in four hundred of these animals is albino. When albino tadpoles hatch, they are almost transparent. This may help camouflage them initially, however, after two weeks, when their hindlegs begin to emerge, they become milky white. A survey in 2001 found hundreds of tiny albinoplains leopard frogs, but when the researcher returned a few months later, not a single albino adult could be found.[39]
Genetic studies of albinism inamphibians have focused on mutations in thetyrosinase gene. The albinophenotype of thenorthern leopard frog (Lithobates pipiens) has been attributed to a failure inpost-translational control in a singlerecessive tyrosinase gene which still has some tyrosinase andDOPAoxidase activity. This is in contrast withmammals, some of which have mutations that show no tyrosinase or DOPA oxidase activity in albinos.[69] The albino phenotype of thepond frog (Pelophylax nigromaculatus) has been attributed to one of three mutations that created a dysfunctional tyrosinase. Two of those mutations involve an insertion of athymine (T), aframeshift mutation, resulting in a truncatedisoform of the TYR protein that is defective. The other mutation involves the deletion of acodon, threenucleotides that code for alysine (Lys). In thewrinkled frog (Glandirana rugosa) and in therice frog (Fejervarya kawamurai), a substitution from aguanine (G) to anadenine (A) creates amissense mutation, in which aglycine (Gly) changes to anaspartic acid (Asp) and anarginine (Arg), respectively. These changes in thepolypeptide chain causes a dysfunctional tyrosinase.[70]
Albinoaxolotl (an amphibian) are also used widely in the laboratory as their transparent skin allows observation of the underlying tissues during limb regeneration.
Albinism inmolluscs has been recognized to be a hereditary phenomenon at least since 1900.[71] Albinism in molluscs can exist to a variable degree. Sometimes an individual snail has a normally pigmented body, but the shell is completely without the normal pigmentation because of a defect in the cells of themantle. Shells of certain mollusc species can be translucent when they lack the normal pigmentation.[72]
Normal (left) and albinistic (right) forms of theland snailPseudofusulus varians. Note that in the albino both the body and the shell are lacking the normal pigmentation.
Albino freshwater snailBiomphalaria glabrata showing the red oxygen-transport pigmenthaemoglobin. Without its normal pigment, the shell of this species is translucent.
The neurohormone [His7]-corazonin induces darkening of the cuticle ofLocusta migratoria. The Okinawa strain of this species is deficient in [His7]-corazonin and is albino. One of the typical features ofLocusta migratoria is that they are gregarious locusts. However, the albino strain shows more solitarious behaviour.[73]
Theyellow mutation infruit flies is a mutation causing a congenital lack of normal pigment; it is a similar phenomenon to albinism in other organisms.[74]
The Japanese sea cucumber (Apostichopus japonicus) is anechinoderm that is caught in the wild or cultivated for food.Normal Japanese sea cucumbers start to develop pigmentation when they are about 1 cm long. The upperside becomes a dull, yellowish -brown to maroon and the underside a light brown. The body walls of adult, albino Japanese sea cucumbers contain only 0.24% melanin compared to 3.12% in normal adults. The difference in melanin content becomes visually apparent at 60 days of age. Theepidermis is thinner in the albinos and contains fewer melanocytes. Albino individuals are similar to normal individuals in growth rate, digestion rate and fertility.[75]
Astaxanthin is the main carotenoid in marine crustaceans (and fish). It has been shown that adding astaxanthin to the feed can improve the skin and muscle colour of marine organisms and thereby increase their commercial and ornamental value.[75]
"Depigmented" arthropods have been found, usually in cave populations.[76]"Albino" individuals of normally red citrus red mites (Panonychus citri) occasionally appear in laboratory colonies, however, these still contain green and yellow pigments. This albinism does not affect mortality.[77]
In some animals, albinism-like conditions may affect other pigments or pigment-production mechanisms:
"Whiteface", a condition that affects some parrot species, is caused by a lack of psittacins.[78]A leucistic alligator at theAudubon Aquarium of the Americas, New Orleans, Louisiana
Axanthism is a condition common in reptiles and amphibians, in whichxanthophoremetabolism is affected rather thansynthesis of melanin, resulting in reduction or absence of red and yellow pteridine pigments.[79]
Leucism differs from albinism in that the melanin is, at least, partially absent but the eyes retain their usual colour. Some leucistic animals are white or pale because ofchromatophore (pigment cell) defects, and do not lack melanin.
Melanism is the direct opposite of albinism. An unusually high level of melanin pigmentation (and sometimes absence of other types of pigment in species that have more than one) results in an appearance darker than non-melanistic specimens from the samegene pool.[80]
An albinoRebutia seedling. The two seedlings are of the same age, but the albino stopped developing once the seed's reserve was exhausted.The foliage of an Albino redwood. Note the distinctive white coloration of the needles.
In plants, albinism is characterised by partial or complete loss ofchlorophyll pigments and incomplete differentiation of chloroplast membranes. Albinism in plants interferes withphotosynthesis, which can reduce survivability.[9] Some plant variations may have white flowers or other parts. However, these plants are not totally devoid of chlorophyll. Terms associated with this phenomenon are "hypochromia" and "albiflora".[10]
Plants that are pale simply from being in the dark are termedetiolated.
Albino redwoods are rare examples of an albino tree with white needles; despite its lack of chlorophyll, it may grow to substantial size as aparasite, usually on the base of the (normal) redwood tree from which it first grew.[81][82][83] Only about sixty examples of albino redwoods are known.[82] Additionally, an even smaller number of "chimeric" redwood trees have both normal and white needles.
^Taylor, J. D. (1969). "The effects of intermedin on the ultrastructure of amphibian iridophores".General and Comparative Endocrinology.12 (3):405–416.doi:10.1016/0016-6480(69)90157-9.PMID5769930.
^Needham, A. E. (2012).The Significance of Zoochromes. Springer. p. 325.ISBN978-3-642-80766-4.Some dominant chromogenic mutations are known and in fact there are more than predicted by the Haldane-Fisher theory of evolution of wild type dominance (Searle, 1968, p. 250)"..."Of 32 dominant mutations known in the mouse as many as nine are chromogenic (Hadorn, 1961, p. 132). This is a very high percentage of the 40 coal-colour genes known among the mouse and implies that dominant mutations are rather characteristic of colour genes. Thedilation gene of the palomino horse is dominant and there is a dominant white in many mammals so that dominance/recessivity is not necessarily positively correlated with excess/deficiency. the dominant white is not so deficient in pigment as the true albino and in particular as the normal eye-pigmentation, so that in Atz' lobster the pigmentation of this organ can be controlled independently of that integument. It would seem that the retention of essential pigment by the dominant white has been naturally selected and that presumably its whole phenotype has been selected. Arctic white races and species no doubt have this type of allele. True recessive albinos lack tyrosinase (Onslow, 1917; Foster, 1952; Barnicott, 1957; Fitzpatrick et al., 1958) or have the enzyme but no free tyrosine (Verne, 1926, p. 535; Fox and Vevers, 1960, p. 37) but in the dominant white the enzyme is present in the skin, under inhibition.
^Nakamura, K.; Ozaki (June 2001). "Genetic mapping of the dominant albino locus in rainbow trout (Oncorhynchus mykiss)".Molecular Genetics and Genomics.265 (4):687–693.doi:10.1007/s004380100464.PMID11459189.S2CID7868741.
^Allison, W. T.; Hallows, T. E.; Johnson, T.; Hawryshyn, C.W.; Allen, D. M. (2006). "Photic history modifies susceptibility to retinal damage in albino trout".Visual Neuroscience.23 (1):25–34.doi:10.1017/s0952523806231031.PMID16597348.S2CID26337580.
^Fausto-Sterling, Anne (2008).Myths Of Gender: Biological Theories About Women And Men (Rev. ed.). Basic Books. p. 172.ISBN978-0-7867-2390-4.Consider albino animals of the arctic. Hungry predators may have unwittingly selected for the albino color variant by eating more of the easily visible dark-colored variants.
^Ilo Hiler, Albinos.Young Naturalist. The Louise Lindsey Merrick Texas Environment Series, No. 6, pp. 28–31. Texas A&M University Press, College Station (1983)
^Pierce, Benjamin A. (2008).Transmission and Population Genetics. Macmillan. p. A1.ISBN978-1-4292-1118-5.In the Hopi culture, albinos were considered special and given special status. Because extensive exposure to sunlight could be damaging or deadly, Hopi male albinos did no agricultural work. Albinism was considered a positive trait rather than a negative physical condition, allowing albinos to have more children and thus increasing the frequency of the allele.
^Shepherd, Rosamond (1996).Founder Effects in Some Victorian Wild Rabbit Oryctolaguscuniculus L. Populations(PDF). Field Naturalists' Club of Victoria. p. 100.There is no apparent reason why selection for albinism should have been greater at Morton Plains thanelse where in north-western Victoria. It is likely that its high occurrence there is a founder effect from the domestic-type feral population established during the 1860s.
^abcFertl, D.; Rosel, P. E. (2008). "Albinism". In Perrin, William F.; Würsig, Bernd; Thewissen, J. G. M. (eds.).Encyclopaedia of Marine Mammals (2nd ed.). Amsterdam: Elsevier. pp. 22–24.ISBN978-0-12-373553-9.
^Hoste, B.; Simpson, S. J.; Tanaka, S.; De Loof, A.; Breuer, M. (2002). "A comparison of phase-related shifts in behavior and morphometrics of an albino strain, deficient in [His7]-corazonin, and a normally coloredLocusta migratoria strain".Journal of Insect Physiology.48 (8):791–801.doi:10.1016/s0022-1910(02)00106-3.PMID12770057.
^abZhao, H.; Chen, M.; Yang, H. (2015). "Albinism". In Yang, Hongsheng; Hamel, Jean-Francois; Mercier, Annie (eds.).The Sea CucumberApostichopus japonicus: History, Biology and Aquaculture.Academic Press. pp. 211–226.ISBN978-0-12-799953-1.
^Locket, N. A. (1986). "Albinism and eye structure in an Australian scorpion,Urodacus yaschenkoi (Scorpiones, Scorpionidae)".Journal of Arachnology.14 (1):101–115.JSTOR3705557.
^"Feather Colors: What We See"Archived March 28, 2009, at theWayback Machine by Dr. Julie Feinstein of the American Museum of Natural History (NY), inBirder's World Magazine online archive; sourced December 2006, actual authoring/publication date unspecified.
^Kerr, E. A. (1963). "Inheritance of crinkle, variegation, and albinism in sweet cherry".Canadian Journal of Botany.41 (10):1395–1404.Bibcode:1963CaJB...41.1395K.doi:10.1139/b63-122.
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