Misplaced Pages

#953046

73-403: BALB/c is an albino , laboratory-bred strain of the house mouse from which a number of common substrains are derived. Now over 200 generations from New York in 1920, BALB/c mice are distributed globally, and are among the most widely used inbred strains used in animal experimentation . The founding animals of the strain were obtained by Halsey J. Bagg of Memorial Hospital, New York, from

146-483: A buffalo in Jamestown, North Dakota , and inspiration for Herman Melville 's novel Moby-Dick , a sperm whale known as Mocha Dick . 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

219-523: A toque macaque ( M. sinica ), rhesus macaque ( M. mulatta ), and bonnet macaque ( M. radiata ). Albinism was observed in jungle cats ( Felis chaus ) and jackals ( 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

292-640: A "low mammary tumour incidence", but do develop other types of cancers in later life, most commonly reticular neoplasms, lung tumours , and renal tumours . Most substrains have a "long reproductive life-span", are noted for displaying high levels of anxiety and for being relatively resistant to diet-induced atherosclerosis , making them a useful model for cardiovascular research. There are noted differences between different BALB/c substrains, though these are thought to be due to mutation rather than genetic contamination. For example, male BALB/c mice are aggressive and will fight other males if housed together. However,

365-534: A "semi-lethal mutation". Pigmentation disorders such as albinism are occasionally associated with hearing impairments in mice, rats, guinea pigs and cats. Intentionally bred albinistic strains of some animal species are commonly used as model organisms in biomedical research and also as pets. Examples include the BALB/c mouse and Wistar and Sprague Dawley rat strains, laboratory rabbits and ferrets. Some researchers have argued that albino animals are not always

438-655: A colour resulting from selective colour 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 include plant pigments and flower pigments . Animals can appear coloured due to two mechanisms, pigments and structural colours . Animals may have both biological pigments and structural colours, for example, some butterflies with white wings. Many animal body-parts, such as skin , eyes , feathers , fur , hair , scales and cuticles, contain pigments in specialized cells called chromatophores . These cells are found in

511-493: A condition called agouti , they make multi-coloured individual hairs. The production of melanin occurs in melanocytes in a complex process involving the enzyme tyrosinase . 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

584-446: A dark ring encircling the iris on some individuals, but is a result of the optical properties of the region between the cornea and sclera , not of pigments in the iris. Iris color is a highly complex phenomenon consisting of the combined effects of texture, pigmentation, fibrous tissue, and blood vessels within the iris stroma , which together make up an individual's epigenetic constitution in this context. An organism's "eye color"

657-458: A dominant albinism in the rainbow trout . 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 albino koala . In mammals, albinism occurs once in every 10,000 births, but in birds,

730-503: A fire destroyed the main Jackson Laboratory buildings in 1947, all of Snell's original breeding stock perished, but Scott's mice were in a different building and survived. Scott donated stock back, at generation 41, to repopulate the colony. The progeny of these are now termed BALB/cJ and, as of 14 December 2006, were 221 generations from the founding stock. Other less popular substrains, such as BALB/cWt , are maintained at

803-546: A fungus, such as Lacazia loboi . Famous albino mammals include Migaloo , a humpback whale living off the coast of Australia; Pinky , a bottlenose dolphin living in and around in Calcasieu Lake , Louisiana; Carolina Snowball, a popular albino bottlenose dolphin displayed at the Miami Seaquarium in the early 1960s; Snowflake , a Barcelona Zoo gorilla , and Mahpiya Ska , ( Sioux for White Cloud),

SECTION 10

#1732772333954

876-437: A genetic basis. Well-known examples are flamingos , 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 next moult . 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

949-403: A good diagnostic feature with which to distinguish leucistic and albino individuals – the colour of the eye." However, there are multiple forms of albinism – currently seven types recognised for humans – most of which do not result in red or pink pupils. The term "partial albino" is sometimes used in the literature. However, it has been stated that "A common misnomer is 'partial albino' – this

1022-627: 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 protective camouflage 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. The lower survival rate of animals with albinism in certain environments has been documented, however, it has been stated that in studies where animals had many places to hide, predators captured albino and normally coloured animals at

1095-420: A medical condition that they were born with" and "a person or animal with white skin and hair and pink eyes" 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". Other definitions of albinism encompass most of the major animal taxa, but ignore

1168-529: A mouse dealer in Ohio in 1913. The name BALB is a portmanteau of "Bagg" and "Albino." From 1920, the progeny of the original colony were systematically inbred , sibling to sibling, for 26 generations over 15 years. During this time, the colony passed through the care of a number of scientists, including C.C. Little and E.C. MacDowell at the Carnegie Institution of Washington and H.J. Muller at

1241-471: A substrain at the University of California, San Francisco . In 1974, now 136 generations from the original breeding pair, these animals were returned to The Jackson Laboratory and were named BALB/cByJ . On 16 November 2005, The Jackson Laboratory reported this substrain had reached its 235th generation. Snell also provided a colleague, J. Paul Scott, with some BALB/c breeding stock in 1938 or 1939. When

1314-501: A white beak, white plumage, non-coloured skin, white talons 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 the common house martin and the American robin . Famous albino birds include " Snowdrop ", a Bristol Zoo penguin . In one study, albinism in birds has been categorised according to the extent of pigment absence. However, it has been argued that

1387-449: A wide range of animals including amphibians , fish , reptiles , crustaceans and cephalopods . Mammals and birds , in contrast, have a class of cells called melanocytes for colouration. The term chromatophore can also refer to coloured, membrane-associated vesicles found in some forms of photosynthetic bacteria . Chromatophores are largely responsible for generating skin and eye colour in poikilothermic animals and are generated in

1460-458: Is a clearly defined set of seven types of genetic mutations which reduce or completely prevent the synthesis of eumelanin or pheomelanin , resulting in reduced pigmentation. Type I oculocutaneous albinism (OCA1a) is the form most commonly recognised as 'albino' as this results in a complete absence of melanin 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

1533-404: Is a common misconception that all albino animals have characteristic pink or red eyes (resulting from the lack of pigment in the iris allowing the blood vessels of the retina to be visible); this is not the case for some forms of albinism. Familiar albino animals include in-bred strains of laboratory animals (rats, mice and rabbits), but populations of naturally occurring albino animals exist in

SECTION 20

#1732772333954

1606-470: Is actually the color of one's iris, the cornea being transparent and the white sclera entirely outside the area of interest. Melanin is yellowish to dark hazel in the stromal pigment cells, and black in the iris pigment epithelium , which lies in a thin but very opaque layer across the back of the iris. Most human irises also show a condensation of the brownish stromal melanin in the thin anterior border layer, which by its position has an overt influence on

1679-640: 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. Most forms of albinism follow a recessive pattern of inheritance. However, this is not always the case. In palomino 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 produce tyrosinase , and have normal eye pigmentation. In Japan, research has identified

1752-504: Is derived from the Greek word for " rainbow ", also its goddess plus messenger of the gods in the Iliad , because of the many colours of this eye part. The iris consists of two layers: the front pigmented fibrovascular layer known as a stroma and, behind the stroma, pigmented epithelial cells. The stroma is connected to a sphincter muscle ( sphincter pupillae ), which contracts

1825-404: Is located on the inner border. The back surface is covered by a heavily pigmented epithelial layer that is two cells thick (the iris pigment epithelium), but the front surface has no epithelium. This anterior surface projects as the dilator muscles. The high pigment content blocks light from passing through the iris to the retina, restricting it to the pupil. The outer edge of the iris, known as

1898-549: Is not possible since albinism affects the whole plumage of a bird, not just part" 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' ". Conditions that are commonly termed "partial albino" include neural crest disorders such as piebaldism , Waardenburg syndrome , or other depigmentation conditions such as vitiligo . These conditions result from fundamentally different causes to

1971-530: Is not the case. In plants, albinism is characterised by partial or complete loss of chlorophyll pigments and incomplete differentiation of chloroplast membranes. Albinism in plants interferes with photosynthesis , which can reduce survivability. 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". Biological pigments are substances produced by living organisms that have

2044-433: 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

2117-415: Is seen; if not, they will remain blue or gray. All the contributing factors towards eye color and its variation are not fully understood. Autosomal recessive/dominant traits in iris color are inherent in other species, but coloration can follow a different pattern. Heterochromia (also known as a heterochromia iridis or heterochromia iridum) is an ocular condition in which one iris is a different color from

2190-604: The BALB/Lac substrain is much more docile. The BALB/cWt is also unusual in that 3% of progeny display true hermaphroditism . The BALB/cJ mice have a medium lifespan of about 17 months for males and 20 months for females, and the body weight at 9 weeks after birth is about 27 g (0.95 oz) for males and 21 g (0.74 oz) for females. Albino Albinism is the congenital absence of melanin in an animal or plant resulting in white hair, feathers, scales and skin and reddish pink or blue eyes. Individuals with

2263-542: The University of Texas at Austin . By 1935 the animals were in the possession of Muller's student, George Davis Snell , who moved them to The Jackson Laboratory . This stock provided the basis of all the BALB/c substrains that are now in use around the world. Snell provided some animals from this stock to the National Institutes of Health (NIH) to maintain. In 1961 D. W. Bailey used some of these to generate

BALB/c - Misplaced Pages Continue

2336-406: The depth of field . Very few humans possess the ability to exert direct voluntary control over their iris muscles, which grants them the ability to dilate and constrict their pupils on command. However, there is no clear purpose or advantage to this. The iris is usually strongly pigmented , with the color typically ranging between brown, hazel, green, gray, and blue. Occasionally, the color of

2409-449: The neural crest during embryonic development. Mature chromatophores are grouped into subclasses based on their colour under white light: Animals can also appear coloured due to structural colour , the result of coherent scattering perceived as iridescence . 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

2482-529: The Albino Squirrel Preservation Society. They have also been protected in studies on their ecology, sociology and behaviour. Studies on medaka 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. Early studies on fish led some researchers to describe albinism as

2555-533: The First was dubbed dikoros (having two irises) for his patent heterochromia since his right iris had a darker color than the left one. In contrast, heterochromia and variegated iris patterns are common in veterinary practice. Siberian Husky dogs show heterochromia, possibly analogous to the genetically determined Waardenburg syndrome of humans. Some white cat fancies (e.g., white Turkish Angora or white Turkish Van cats) may show striking heterochromia, with

2628-533: The Jackson Laboratory, while the BALB/cN substrain is maintained by the NIH. BALB/c mice are useful for research into both cancer and immunology. According to Michael Festing's Inbred Strains of Mice , BALB/c substrains are "particularly well known for the production of plasmacytomas on injection with mineral oil ," an important process for the production of monoclonal antibodies . They are also reported as having

2701-443: The anterior ciliary body provide a secondary pathway for aqueous humour to drain from the eye. The iris is divided into two major regions: The collarette is the thickest region of the iris, separating the pupillary portion from the ciliary portion. The collarette is a vestige of the coating of the embryonic pupil. It is typically defined as the region where the sphincter muscle and dilator muscle overlap. Radial ridges extend from

2774-488: The behaviour of albinos in the wild, e.g. leaping from branch to branch, is similar to pigmented squirrels. A 2012 survey of the literature reported that in India, there were several records of albino mammals including the tiger , lesser mouse-tailed bat , chital , common palm civet , northern palm squirrel , five-striped palm squirrel and wild boar . Albino macaques have been reported in several occasions including

2847-476: The best choice for scientific studies due to the consequences of albinism (e.g. hearing and visual impairments). 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. It is doubtful whether these individuals would have survived to become adults without the protection and care they receive in captivity. It has been claimed that "Squirrels are

2920-619: The blood vessels, collagen in the vessel and stroma) is the most important element. Rayleigh scattering and Tyndall scattering , (which also happen in the sky) and diffraction also occur. Raman scattering , and constructive interference , as in the feathers of birds, do not contribute to the color of the eye, but interference phenomena are important in the brilliantly colored iris pigment cells ( iridophores ) in many animals. Interference effects can occur at both molecular and light-microscopic scales, and are often associated (in melanin-bearing cells) with quasicrystalline formations, which enhance

2993-413: 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 the eastern 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

BALB/c - Misplaced Pages Continue

3066-416: 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 include mother 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. The primary function of pigments in plants is photosynthesis , which uses

3139-422: The condition are referred to as albinos . 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 hours due to the lack of protection from UV radiation and their lack of camouflage to avoid predators. It

3212-407: 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. Melanin protects the skin from ultra-violet radiation in sunlight. Melanosomes block harmful electromagnetic radiation from the sun while allowing beneficial frequencies to enter the body. This means some animals may die from UV radiation due to

3285-694: The costs, some individuals do reach adult age and breeding status. 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 seven pinniped species but there were no known reports of anomalously white sea otters ( Enhydra lutris ) or sirenians . Whales and dolphins also may appear white if extensively scarred, or covered with

3358-896: 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'. As with other animals, it has been stated that for fish to be properly described as "albino", they must have a white body and pink or red eyes. Zebrafish have three types of chromatophores—iridophores, melanophores, and xanthophores—which produce silver, black, and yellow pigmentation respectively. Zebrafish that lack iridophores are known as roy mutants , those that lack melanophores as albino mutants , and those which lack both melanophores and iridophores are ruby 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. In mammals, albinism

3431-590: The green pigment chlorophyll along with several red and yellow pigments including porphyrins , carotenoids , anthocyanins and betalains . 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

3504-497: The inner ear, meaning that hearing in fishes is less likely to be affected by albinism than in mammals. 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. The incidence of albinism can be artificially increased in fish by exposing the eggs to heavy metals (e.g. arsenic, cadmium, copper, mercury, selenium, zinc). Iris (anatomy) The word "iris"

3577-405: The iris is due to a lack of pigmentation, as in the pinkish-white of oculocutaneous albinism , or to obscuration of its pigment by blood vessels, as in the red of an abnormally vascularised iris. Despite the wide range of colors, the only pigment that contributes substantially to normal iris color is the dark pigment melanin . The quantity of melanin pigment in the iris is one factor in determining

3650-419: The layers of the iris are: The stroma and the anterior border layer of the iris are derived from the neural crest , and behind the stroma of the iris, the sphincter pupillae and dilator pupillae muscles, as well as the iris epithelium, develop from optic cup neuroectoderm. The iris controls the size of the pupil by means of contracting the iris sphincter muscle and/or the iris dilator muscle . The size of

3723-521: 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. Albinism can also occur in marsupials and monotremes , such as echidnas , kangaroos , koalas , possums , wallabies and wombats . 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

SECTION 50

#1732772333954

3796-452: The most common pattern being one uniformly blue, the other copper, orange, yellow, or green. Striking variation within the same iris is also common in some animals, and is the norm in some species. Several herding breeds, particularly those with a blue merle coat color (such as Australian Shepherds and Border Collies ) may show well-defined blue areas within a brown iris, as well as separate blue and darker eyes. Some horses (usually within

3869-613: 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 the red blood cells in the retina 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 lose photoreceptors due to apoptosis . In all albino mammals studied,

3942-425: The only known albino mammal to survive successfully in the wild". 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

4015-446: The optical effects. Interference is recognised by characteristic dependence of color on the angle of view, as seen in eyespots of some butterfly wings , although the chemical components remain the same. White babies are usually born blue-eyed since no pigment is in the stroma, and their eyes appear blue due to scattering and selective absorption from the posterior epithelium. If melanin is deposited substantially, brown or black color

4088-410: The other iris (complete heterochromia), or where the part of one iris is a different color from the remainder (partial heterochromia or sectoral heterochromia). Uncommon in humans, it is often an indicator of ocular disease, such as chronic iritis or diffuse iris melanoma, but may also occur as a normal variant. Sectors or patches of strikingly different colors in the same iris are less common. Anastasius

4161-414: The other stromal components. Sometimes, lipofuscin , a yellow "wear and tear" pigment, also enters into the visible eye color, especially in aged or diseased green eyes. The optical mechanisms by which the nonpigmented stromal components influence eye color are complex, and many erroneous statements exist in the literature. Simple selective absorption and reflection by biological molecules ( hemoglobin in

4234-510: The overall color. The degree of dispersion of the melanin, which is in subcellular bundles called melanosomes , has some influence on the observed color, but melanosomes in the iris of humans and other vertebrates are not mobile, and the degree of pigment dispersion cannot be reversed. Abnormal clumping of melanosomes does occur in disease and may lead to irreversible changes in iris color (see heterochromia , below). Colors other than brown or black are due to selective reflection and absorption from

4307-455: The periphery to the pupillary zone, to supply the iris with blood vessels. The root of the iris is the thinnest and most peripheral. The muscle cells of the iris are smooth muscle in mammals and amphibians, but are striated muscle in reptiles (including birds). Many fish have neither, and, as a result, their irises are unable to dilate and contract, so that the pupil always remains of a fixed size. From anterior (front) to posterior (back),

4380-413: The phenotypic eye color of an organism. Structurally, this huge molecule is only slightly different from its equivalent found in skin and hair . Iris color is due to variable amounts of eumelanin (brown/black melanins) and pheomelanin (red/yellow melanins) produced by melanocytes. More of the former is found in brown-eyed people and of the latter in blue- and green-eyed people. The limbal ring appears as

4453-408: The pupil in a circular motion, and a set of dilator muscles ( dilator pupillae ), which pull the iris radially to enlarge the pupil, pulling it in folds. The sphincter pupillae is the opposing muscle of the dilator pupillae. The pupil's diameter, and thus the inner border of the iris, changes size when constricting or dilating. The outer border of the iris does not change size. The constricting muscle

SECTION 60

#1732772333954

4526-401: The pupils is dependent on many factors (including light, emotional state, cognitive load, arousal, stimulation), and can range from less than 2 mm in diameter, to as large as 9 mm in diameter. However, there is considerable variation in maximal pupil diameter by individual humans, and decreases with age. The irises also contract the pupils when accommodation is initiated, to increase

4599-403: The rate is once in every 1,764 births. 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. Melanin has several functions in most mammals and other animals; these are disrupted by albinism. Melanin functions in

4672-445: The root, is attached to the sclera and the anterior ciliary body . The iris and ciliary body together are known as the anterior uvea . Just in front of the root of the iris is the region referred to as the trabecular meshwork , through which the aqueous humour constantly drains out of the eye, with the result that diseases of the iris often have important effects on intraocular pressure and indirectly on vision. The iris along with

4745-559: The same rate. Furthermore, in certain species, albino animals may be excluded from families or other groups, or rejected as mates. On the other hand, there is also evidence for positive selection for albinism in some animals, as well as cultural selection favoring albino people in some human societies, which results in the increase of genes associated with albinism. The founder effect may explain why some animal populations become selected for albinism. The novelty of albino animals has occasionally led to their protection by groups such as

4818-652: The seven types of oculocutaneous albinism that have been identified in humans (and confirmed in some other animals) and the use of the term "partial albino" is therefore misleading. 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", 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

4891-413: 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." 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

4964-420: 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", however, this ignores the effects of other pigments and structural colours. An albino bird has

5037-594: 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, the albino 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." 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

5110-521: The varied use and interpretation of the term "albino", written reports of albinistic organisms can often not be verified. 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) and pheomelanin (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

5183-446: The white, spotted, palomino, or cremello groups of breeds) may show amber, brown, white and blue all within the same eye, without any sign of eye disease. One eye with a white or bluish-white iris is also known as a "walleye". Iridology (also known as iridodiagnosis) is an alternative medicine technique whose proponents believe that patterns, colors, and other characteristics of the iris can be examined to determine information about

5256-423: The wild, e.g., Mexican cave tetra . Albinism is a well-recognized phenomenon in molluscs, both in the shell and in the soft parts. It has been claimed by some that albinism can occur for a number of reasons aside from inheritance, including genetic mutations, diet, living conditions, age, disease, or injury. However, this is contrary to definitions where the condition is inherited. Oculocutaneous albinism (OCA)

5329-535: 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. A study on albinistic prairie voles ( Microtus ochrogaster ) found that albinism in this species conferred an advantage for

#953046