Polydactyl cat

Embryologists distinguish two principal forms of feline polydactyly: preaxial and postaxial. Preaxial polydactyly involves supernumerary digits on the medial (inner) side of the paw, corresponding to the thumb side in humans, whereas postaxial polydactyly affects the lateral (outer) side, corresponding to the little finger. Postaxial polydactyly is comparatively rare in cats, and the additional digits in such cases are often incompletely formed. By contrast, preaxial extra digits are typically well developed. SHH encodes a signalling protein that plays a central role in embryonic pattern formation, including the specification and growth of limbs and digits. Genetic work studying the DNA basis of the condition indicates that many different mutations in the same ZRS area can all lead to polydactyly. An identical sequence at this position serves the same function in human and mice and cause similar symptoms when mutated. Different mutations have different specific effects: for example, while the Hw mutant tends to mostly induce extra fingers in the fore limbs, many other mutations affect the posterior limbs too. The mentioned form of polydactyly of the Hw mutant shows a biased variation. In a recent empirical study first the number of extra toes of 375 mutant Maine Coon cats were variable (polyphenism) and second, the number of extra toes followed a discontinuous statistical distribution. They were not equally distributed as one might expect of an identical single point mutation. The example demonstrates that the variation is not explained completely by the mutation alone. == Occurrence and heritability ==

Normal cats have a total of 18 toes, with five toes on each fore paw, and four toes on each hind paw; polydactyl cats may have as many as nine digits on their front or hind paws. Various combinations of anywhere from four to seven toes per paw are common. Polydactyly is a congenital abnormality that can be inherited in an autosomal dominant manner, meaning only one mutated gene needs to be passed on from the parent for the offspring to express the mutated phenotype. Various combinations of anywhere from four to seven toes per paw are common. Polydactyly does not affect the lifespan of the cat, nor does it cause any health issues. One suggestion for caring for cats with polydactyly is to ensure that their nails are trimmed frequently so that their claws do not become overgrown and curl into their paws. It is also imperative to make sure that polydactyl cats, especially when they are young, do not get their claws stuck, since that can be more common for cats with extra toes. ==Breeding==

Polydactylism is found in random-bred cat populations, and not an indication of purebred ancestry. Polydactylism is considered a disqualifying fault in most breeds, and makes kittens of any breeding line inadmissible for registration with some of the major cat registries. The registries argue that polydactylism is a congenital abnormality, which confers no welfare benefit upon cats, and in some cases the additional toes may be prone to injury; furthermore, claws on the extra toes may fail to wear down naturally, potentially causing harm to the animal. Due to these welfare concerns, polydactyl cats are barred from registry and showing in for example the FIFe, GCCF, This also holds true for oligodactylism (less toes) in some registries. The American polydactyl is recognized as a cat breed with the Rare and Exotic Feline Registry, however not by any of the major registries. The cats are selectively bred in compliance with a breed standard in order to maintain a standardized breed with specific physical and behavioral characteristics, in addition to extra digits. However, in non-pedigree breeding, polydactyly is commonly selected for because humans believe that the mutation is valuable aesthetically (in other words, people think it is cute), meaning this is an example of artificial selection, though there is no significant advantage to the mutation. Breeders typically breed a polydactyl cat with a normal-toed cat since the trait is passed on dominantly and reliable to the offspring, meaning breeders can breed a litter of polydactyl kittens only requiring one polydactyl parent. == History and naming ==

The condition seems to be most commonly found in cats along the East Coast of North America (in the United States and Canada) and in Western England and Wales. Upon Hemingway's death in 1961, his former home in Key West, US, became a museum and a home for his cats, and it currently houses approximately 50 descendants of his cats (about half of which are polydactyl). Other nicknames for polydactyl cats include mitten cats, conch cats, boxing cats, mitten-foot cats, snowshoe cats, boston-toed cats, "providence cats", thumb cats, six-fingered cats, and Cardi-cats. ==See also==