These are just a few examples of animals with this quality, but it is most pronounced in the butterfly family. Some definitions are too broad to be of much use, e. Structural colour differs according to the observer's position whereas pigments appear the same regardless of the angle-of-view. In nearly all mammals, the overwhelming majority of photoreceptors are rods rather than cones. These cells are found in a wide range of animals including amphibians , fish , reptiles , crustaceans and cephalopods. Nor do they include plants. The condition is most commonly seen in birds, reptiles and amphibians, but more rarely seen in mammals and other taxa. This is because other hormones and proteins are involved in melanin production, the presence of which is genetically determined. 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.
For example, the albino gaur has this name because it is ash-grey whereas other gaur are almost black, and the American albino horse is a chestnut with a dilution gene. The survival rate of animals with albinism in the wild can be low,   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. Furthermore, it could be interpreted that " This is because other hormones and proteins are involved in melanin production, the presence of which is genetically determined. Some albino animals may have pale-blue eyes due to other colour generating processes. Light typically passes through multiple layers and is reflected more than once. 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. 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. Mammals have a gene that codes for the presence of tyrosinase in cells — called the TYR gene. Structural colour differs according to the observer's position whereas pigments appear the same regardless of the angle-of-view. If this gene is altered or damaged, melanin cannot be reliably produced and the mammal becomes an albino. In contrast, the retina of birds is cone rich meaning that the vision of albino birds is affected less than albino mammals. Chromatophores are largely responsible for generating skin and eye colour in poikilothermic animals and are generated in the neural crest during embryonic development. Some definitions are too broad to be of much use, e. Some definitions of albinism, whilst taking most taxa into account, ignore others. Mammals and birds , in contrast, have a class of cells called melanocytes for colouration. Definition[ edit ] Albino wallaby with her offspring Definitions of albinism vary and are inconsistent. 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. They have also been protected in studies on their ecology and behaviour. In nearly all mammals, the overwhelming majority of photoreceptors are rods rather than cones. Albinism specifically affects the rod cells, but the number and distribution of the cones is unaffected. Melanin is an organic pigment that produces most of the colour seen in mammals. Pigments[ edit ] Many animal body-parts, such as skin , eyes , feathers , fur , hair , scales and cuticles, contain pigments in specialized cells called chromatophores. The condition is most commonly seen in birds, reptiles and amphibians, but more rarely seen in mammals and other taxa. Survival disadvantages[ edit ] Many animals with albinism lack their protective camouflage and are therefore less able to conceal themselves from their predators or prey: Biological colouration[ edit ] Biological pigments are substances produced by living organisms that have a colour resulting from selective colour absorption. The absence of melanin results in abnormal development of eyes and leads to problems with focusing, and depth perception.
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