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41-451: As in other hairless breeds, coated examples can also occur. In hairless examples the skin may be any one of a wide variety of colors, with or without limited unpigmented areas, usually the legs, tail or chest; any hairs may be of any colour. In coated dogs, the coat may be of any colour but merle . Hairless dogs are associated with the Andean civilizations . The modern breed is recognized as

82-419: A merle coat: brown/liver (red merle) and black (blue merle). Associated breeds include Carea Leonés , Australian Shepherds and Catahoula Leopard Dogs . Health issues are more typical and more severe when two merle-patterned dogs are bred together. Merle can affect all coat colors. The merle forms of brown are usually called "red" (though this is not correct; red and brown are genetically different), and black

123-411: A non-merle. This is commonly seen in dogs who are recessive red, clear recessive reds in particular, though patches can still be seen in certain red dogs. In America, a dog with the phantom merle coloring is sometimes described as being "cryptic for merle". A cryptic merle bred to a merle may produce merles, cryptic merles or non-merles, depending on whether the parents were heterozygous or homozygous for

164-506: A part in producing harlequin Great Danes . Depending on the breed, registry or country, the pattern may be register-able with a registry but not allowed in conformation , and the pattern may not be recognized by the breed standard , disqualifying it from showing . There may also be additional requirements for the pattern such as the dog being allowed to have the pattern but must have completely dark eyes with no blue in them. Merle

205-497: A part of the national cultural heritage . The dog has been known by many names, among them Allqu (in Inca times), Quechua : Kaclla , Spanish : Perro calato , Perro chino (which may derive from china , 'woman', rather than indicating a Chinese origin), Perro de Sechura , Perro Chimú , Perro orquídea , Viringo and Vitilingo . The Peruvian Hairless Dog is often perceived to be an Incan dog because it

246-634: A symbol of Peru and part of its national heritage, celebrated in art and literature. The Fédération Cynologique Internationale (FCI) accepted the breed and adopted an official breed standard . Before that time, in the United States, some enthusiasts created another type of Peruvian hairless dog, the Peruvian Inca Orchid. The Peruvian Inca Orchid is recognized by the AKC and all recognized dogs are descendants of 13 dogs brought from Peru in

287-437: Is a variation in coloration most often used to describe color differences of the iris , but can also be applied to color variation of hair or skin . Heterochromia is determined by the production, delivery, and concentration of melanin (a pigment ). It may be inherited , or caused by genetic mosaicism , chimerism , disease , or injury . It occurs in humans and certain breeds of domesticated animals. Heterochromia of

328-407: Is called "blue" as lighter patches of black are formed throughout the coat and look slightly blue in color. Dogs who are recessive red can still be affected by merle, but the patches are either hardly seen or, if the dog is a clear recessive red, are not visible at all. Combinations such as brindle and sable merle exist, but are not typically accepted in breed standards . In addition to altering

369-410: Is concentric, rather than sectoral. The central (pupillary) zone of the iris is a different color than the mid-peripheral (ciliary) zone. Central heterochromia is more noticeable in irises containing low amounts of melanin . Heterochromia of the eye was first described as a human condition by Aristotle , who termed it heteroglaucos . Notable historical figures thought to have heterochromia include

410-709: Is known to have been kept during the Inca Empire (the Spaniards classified them as one of the six different breeds of dogs in the empire), they were also kept as pets in pre-Inca cultures from the Peruvian northern coastal zone. Ceramic hairless dogs from the Chimú , Moche , and Vicus culture are well known. Depictions of Peruvian hairless dogs appear around A.D. 750 on Moche ceramic vessels and continue in later Andean ceramic traditions. Peruvian Hairless Dogs are now

451-458: Is more frequently observed in species of domesticated mammals. The blue eye occurs within a white spot, where melanin is absent from the skin and hair (see Leucism ). These species include the cat , particularly breeds such as Turkish Van , Khao Manee and (rarely) Japanese Bobtail . These so-called odd-eyed cats are white, or mostly white, with one normal eye (copper, orange, yellow, green), and one blue eye. Among dogs , complete heterochromia

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492-406: Is not accepted. The eye color is linked to the skin color. It is always brown, but dogs with light colors can have clearer eyes than darker-skinned dogs. Peruvian Hairless Dogs come in three sizes: Weight is also varied according to size : The dogs should be slim and elegant, with the impression of force and harmony, without being coarse. The ears should be candle-flame shaped and erect with

533-486: Is often classified as either genetic (due to mosaicism or congenital ) or acquired, with mention as to whether the affected iris or portion of the iris is darker or lighter. Most cases of heterochromia are hereditary, or caused by genetic factors such as chimerism, and are entirely benign and unconnected to any pathology, however, some are associated with certain diseases and syndromes. Sometimes one eye may change color following disease or injury. Acquired heterochromia

574-598: Is seen often in the Siberian Husky and few other breeds, usually Australian Shepherd and Catahoula Leopard Dog and rarely in Shih Tzu . Horses with complete heterochromia have one brown and one white, gray, or blue eye—complete heterochromia is more common in horses with pinto coloring. Complete heterochromia occurs also in cattle and even water buffalo . It can also be seen in ferrets with Waardenburg syndrome , although it can be very hard to tell at times as

615-528: Is sometimes introduced to other purebred dog breeds through crossbreeding , but these dogs are not purebred. In 2020 the UK Kennel Club (the oldest in the World) banned the registration of merle Poodles as it is not and never has been a colour pattern recognised in pure Poodles by the club. The merle allele is actually an incompletely dominant allele . If two heterozygote merle dogs are mated, on

656-400: Is usually due to injury, inflammation, the use of certain eyedrops that damage the iris, or tumors, both benign and malignant. Heterochromia has also been observed in those with Duane syndrome . Partial heterochromia is most often a benign trait of genetic origins, but, like complete heterochromia, can be acquired or be related to clinical syndromes. In sectoral heterochromia, areas of

697-963: The Australian Shepherd and Catahoula Leopard Dog , and appears in others, including the Miniature American Shepherd , the Koolie in Australia, the Shetland Sheepdog , various collie breeds, the Cardigan Welsh Corgi , the Pyrenean Shepherd and the Bergamasco Shepherd . In Dachshunds , the merle pattern is known as "dapple". In Beaucerons the merle pattern is known as "harlequin". The merle allele also plays

738-618: The Byzantine emperor Anastasius the First , dubbed dikoros (Greek for 'having two pupils'). "His right eye was light blue, while the left was black, nevertheless his eyes were most attractive", is the description of the historian John Malalas . A more recent example is the German poet, playwright, novelist, scientist, statesman, theatre director, and critic, Johann Wolfgang Goethe . The Alexander Romance , an early literary treatment of

779-437: The eye is called heterochromia iridum or heterochromia iridis . It can be complete, sectoral, or central. In complete heterochromia, one iris is a different color from the other. In sectoral heterochromia, part of one iris is a different color from its remainder. In central heterochromia, there is a ring around the pupil or possibly spikes of different colors radiating from the pupil. Though multiple causes have been posited,

820-459: The United States, and is not associated with lack of genetic diversity. The affected eye may be hyperpigmented (hyperchromic) or hypopigmented (hypochromic). In humans, an increase of melanin production in the eyes indicates hyperplasia of the iris tissues, whereas a lack of melanin indicates hypoplasia . The term is derived from Ancient Greek : ἕτερος , héteros "different" and χρῶμα , chrôma "color". Eye color , specifically

861-412: The average, one-quarter of the puppies will be "double merles", which is the common term for dogs homozygous for the longest versions of the merle alleles, and a high percentage of these double merle puppies could have eye defects or be deaf. Knowledgeable and responsible breeders who want to produce merle puppies mate a merle with a non-merle dog; roughly half the puppies will be merles, and none will have

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902-411: The base coat color, merle also modifies eye color and coloring on the nose and paw pads. The merle allele modifies the dark pigment, resulting in eyes or parts of eyes turning blue. Since merle causes random modifications, dark-eyed, blue-eyed and odd-colored eyes are possible. Pigmentation on paw pads and nose may be mottled by pink. Merle is a distinguishing marking of several breeds, particularly

943-502: The color of the irises, is determined primarily by the concentration and distribution of melanin. Although the processes determining eye color are not fully understood, it is known that inherited eye color is determined by multiple genes . Environmental or acquired factors can alter these inherited traits. The color of the mammalian, including human, iris is very variable. However, there are only two pigments present, eumelanin and pheomelanin . The overall concentration of these pigments,

984-474: The early 20th century. In 2018, an analysis of DNA from the entire cell nucleus indicated that dogs entered North America from Siberia 4,500 years after humans did, were isolated for the next 9,000 years, and after contact with Europeans these no longer exist because they were replaced by Eurasian dogs. The pre-contact dogs exhibit a unique genetic signature that is now gone. According to the FCI breed standard ,

1025-437: The eye color is often a midnight blue. Sectoral heterochromia, usually sectoral hypochromia, is often seen in dogs , specifically in breeds with merle coats. These breeds include the Australian Shepherd , Border Collie , Collie , Shetland Sheepdog , Welsh Corgi , Pyrenean Shepherd , Mudi , Beauceron , Catahoula Cur , Dunker , Great Dane , Dachshund and Chihuahua . It also occurs in certain breeds that do not carry

1066-519: The gene, do not develop in the womb. This results in an average birthrate of 2:1, hairless:coated. Merle (dog coat) Merle is a genetic pattern in a dog 's coat and alleles of the PMEL gene . It results in different colors and patterns and can affect any coats. The allele creates mottled patches of color in a solid or piebald coat, blue or odd-colored eyes , and can affect skin pigment as well. Two types of colored patches generally appear in

1107-453: The health risk associated with these particular homozygous merles and stopped registering puppies produced from merle to merle matings in 2013. Merle to merle mating is currently only forbidden in three breeds. The suppression of pigment cells ( melanocytes ) in the iris and in the stria vascularis of the cochlea (inner ear) leads to blue eyes and deafness. An auditory-pigmentation disorder in humans, Waardenberg syndrome , reflects some of

1148-693: The life of Alexander the Great , attributes heterochromia to him. In it he is described as having one eye light and one eye dark. However, no ancient historical source mentions this. It is used to emphasise the otherworldly and heroic qualities of Alexander. In the Ars Amatoria , the Roman poet Ovid describes the witch Dipsas as having 'double pupils'. Kirby Flower Smith suggested that this could be understood as heterochromia, though other scholars have disagreed. The Roman jurist and writer Cicero also mentions

1189-519: The merle allele. Found only in Great Danes , (and registered as Harlequin). In 2018, a published paper identified six general categories of merle alleles that affect (or do not affect) the final coat color depending on the length of the SINE insertion within them. Dogs with two copies of some versions of the merle allele (called "double merle") have an even higher probability of being deaf and with vision impairments. The UK Kennel Club has acknowledged

1230-411: The merle alleles. Another mutation for cryptic merle has been identified by Dr. Helena Synková, and has been given the working name of "atypical merle". It is recommended that if a breeder is unsure if their dog is merle or not, that they be tested for the merle allele lengths. Certain modifying genes work in tandem (co-dominant expressive) with the merle alleles to create a completely different look to

1271-448: The merle gene affects the eyes, causing blindness. In one study of 38 dachshunds by a German researcher, partial hearing loss was found in 54.6% of double merles and 36.8% of single merles. One out of the 11 (9.1%) double merles was fully deaf while none of the single merles were. Another study done by Texas A&M University found that of 22 double merles, eight were completely deaf and two were deaf in one ear. Of 48 single merles, one

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1312-497: The most important aspect of its appearance is its hairlessness. Hairless dogs are often used in research for testing of various conditions such as dermatitis and other immune-related conditions. The dog may have short hair on top of its head, on its feet, and on the tip of its tail. In Peru, breeders tend to prefer completely hairless dogs. The color of skin can be chocolate-brown, elephant-grey, copper, or mottled. They can be totally one color or one color with tongue pink spots. Albinism

1353-419: The pattern. Often mistaken for a "double merle", a harlequin merle (or just harlequin), is a Great Dane that carries both the merle pattern allele and the co-dominant modifying gene for harlequin, PSMB7 (also known as H). This causes most or all of the diluted "blue" color to be replaced with white, resulting in a dog that is mostly white with black patches. All dogs exhibiting the harlequin pattern also have

1394-424: The possibility to lay flat. Proportions of height (at withers ) to length (withers to base of tail) are 1:1. The gene that causes hairlessness also results in the dogs often having fewer teeth than other breeds, mostly lacking molars and premolars. The hairlessness trait is a dominant double lethal mutation , which means that homozygotic hairlessness does not exist. Homozygous embryos, those with two copies of

1435-685: The problems associated with heterozygous and homozygous merle dogs and genetic research in dogs has been undertaken with the goal of better understanding the genetic basis of this human condition. Dogs who are homozygous for certain merle alleles often have visual and auditory deficits. These dogs are sometimes referred to as "double merle" and sometimes incorrectly referred to as "lethal white". Ocular defects include microphthalmia , conditions causing increased ocular pressure and colobomas , among others. Double merle dogs may be deaf or blind or both, and can carry ocular defects in blue or colored eyes. Currently no studies have been done to prove whether or not

1476-499: The ratio between them, variation in the distribution of pigment in the layers of the stroma of the iris and the effects of light scattering all play a part in determining eye color. In the United States, July 12 is observed by some as National Different Colored Eyes Day. Heterochromia is classified primarily by onset: as either genetic or acquired. Although a distinction is frequently made between heterochromia that affects an eye completely or only partially (sectoral heterochromia), it

1517-716: The same feature of 'double pupils' as being found in some Italic women. Pliny the Elder related this feature to the concept of 'the evil eye '. The twelfth-century scholar Eustathius , in his commentary on the Iliad, reports a tradition in which the Thracian Thamyris (son of the nymph Argiope ), who was famed for his musical abilities, had one eye that was grey, whilst the other was black. W. B. McDaniel suggests that this should be interpreted as heterochromia. Although infrequently seen in humans, complete heterochromia

1558-412: The same iris contain two different colors, the contrasting colors being demarcated in a radial, or sectoral, manner. Sectoral heterochromia may affect one or both eyes. It is unknown how rare sectoral heterochromia is in humans, but it is considered to be less common than complete heterochromia. Central heterochromia is also an eye condition where there are two colors in the same iris; but the arrangement

1599-459: The scientific consensus is that a lack of genetic diversity is the primary reason behind heterochromia, at least in domestic animals. This is due to a mutation of the genes that determine melanin distribution at the 8-HTP pathway, which usually only become corrupted due to chromosomal homogeneity. Though common in some breeds of cats, dogs, cattle and horses due to inbreeding, heterochromia is uncommon in humans, affecting fewer than 200,000 people in

1640-429: The vision or hearing defects associated with double merle dogs. In January 2006, scientists at Texas A&M University announced the discovery of a mobile genetic unit called a retrotransposon , responsible for the various merle mutations in dogs. Merle can be tested for and identified through DNA. A phantom merle or cryptic merle is one with such small patches of merling, or none at all, that it appears to be

1681-474: Was deaf in one ear and none were completely deaf. In another study of 70 dogs, 15 of them Catahoula Curs, 4 of the Catahoulas were deaf, while 86% of the double merles of other breeds were deaf. Deaf and/or blind dogs can live well with proper care. Various internet groups are dedicated to supporting carers of such dogs. Deaf dogs can compete successfully in agility. Heterochromia Heterochromia

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