A polydactyl cat is a

cat The cat (''Felis catus''), also referred to as the domestic cat or house cat, is a small domesticated carnivorous mammal. It is the only domesticated species of the family Felidae. Advances in archaeology and genetics have shown that the ...

with a congenital physical anomaly called

polydactyly Polydactyly is a birth defect that results in extra fingers or toes. The hands are more commonly involved than the feet. Extra fingers may be painful, affect self-esteem, or result in clumsiness. It is associated with at least 39 genetic mut ...

(also known as polydactylism or hyperdactyly), which causes the cat to be born with more than the usual number of toes on one or more of its paws. Cats with this genetically inherited trait are most commonly found along the East Coast of

North America North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...

(in the

United States The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...

and

Canada Canada is a country in North America. Its Provinces and territories of Canada, ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, making it the world's List of coun ...

) and in

South West England South West England, or the South West of England, is one of the nine official regions of England, regions of England in the United Kingdom. Additionally, it is one of four regions that altogether make up Southern England. South West England con ...

and

Wales Wales ( ) is a Countries of the United Kingdom, country that is part of the United Kingdom. It is bordered by the Irish Sea to the north and west, England to the England–Wales border, east, the Bristol Channel to the south, and the Celtic ...

Occurrence

Polydactyly is a congenital abnormality that can be inherited in an

autosomal An autosome is any chromosome that is not a sex chromosome. The members of an autosome pair in a diploid cell have the same morphology, unlike those in allosomal (sex chromosome) pairs, which may have different structures. The DNA in autosome ...

dominant manner. Some cases of polydactyly are caused by mutations in the ZRS, a genetic enhancer that regulates expression of the sonic hedgehog (SHH) gene in the limb. The SHH protein is an important signalling molecule involved in patterning of many body elements, including limbs and digits. 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. Both Jake, a Canadian polydactyl cat, and Paws, an American polydactyl cat, were recognised by

Guinness World Records ''Guinness World Records'', known from its inception in 1955 until 1999 as ''The Guinness Book of Records'' and in previous United States editions as ''The Guinness Book of World Records'', is a British reference book published annually, list ...

as having the highest number of toes on a cat, 28. Various combinations of anywhere from four to seven toes per paw are common. Polydactyly is most commonly found on the front paws only; it is rare for a cat to have polydactyl hind paws only, and polydactyly of all four paws is even less common. File:The multiple toes of a polydactyl kitten.jpg, alt=A white and grey kitten being held up, displaying its extra toes., Kitten with 23 toes File:Male polydactyl grey house cat - right front paw, circles.jpg, alt=The underside of a cat's paw, edited to show seven yellow circles, indicating digits., Right front paw of a polydactyl cat. Circles represent digits. The circle with a question mark indicates what might be a separate digit. The rightmost circle is for a small, underdeveloped, clawless digit. File:Fig 5 29-11-2013-vereinfacht-deutsch.jpg, Preaxial polydactyly, Hemingway mutant: frequency of polydactylous digits per individual File:8 Toed Red Maine Coon Polydactyl Kitten.png, alt=A white and red kitten with six toes on the paw visible., Polydactyl red Maine Coon kitten File:Shh ectopic expression.gif, Preaxial polydactyly: ectopic Shh-expression, Hemingway mutant, mouse, right forelimb File:PawPed-1A.jpg, Preaxial polydactyly: Maine Coon cat, Hemingway mutant, right forefoot File:Conchi polydactyl cat.jpg, A domestic true polydactyl cat

History and folklore

The condition seems to be most commonly found in cats along the East Coast of

(in the

and

) and in Western

England England is a Countries of the United Kingdom, country that is part of the United Kingdom. It is located on the island of Great Britain, of which it covers about 62%, and List of islands of England, more than 100 smaller adjacent islands. It ...

and

. Polydactyl cats have been extremely popular as

ship's cat The ship's cat has been a common feature on many Merchant vessel, trading, History of research ships, exploration, and naval ships dating to ancient times. Cats have been brought on ships for many reasons, most importantly to control rodents. ...

s. Although there is some controversy over whether the most common variant of the trait originated as a mutation in

New England New England is a region consisting of six states in the Northeastern United States: Connecticut, Maine, Massachusetts, New Hampshire, Rhode Island, and Vermont. It is bordered by the state of New York (state), New York to the west and by the ...

or was brought there from

Britain Britain most often refers to: * Great Britain, a large island comprising the countries of England, Scotland and Wales * The United Kingdom of Great Britain and Northern Ireland, a sovereign state in Europe comprising Great Britain and the north-eas ...

, there seems to be agreement that it spread widely as a result of cats carried on ships originating in

Boston, Massachusetts Boston is the capital and most populous city in the Commonwealth (U.S. state), Commonwealth of Massachusetts in the United States. The city serves as the cultural and Financial centre, financial center of New England, a region of the Northeas ...

, and the

prevalence In epidemiology, prevalence is the proportion of a particular population found to be affected by a medical condition (typically a disease or a risk factor such as smoking or seatbelt use) at a specific time. It is derived by comparing the number o ...

of polydactyly among the cat population of various ports correlates with the dates when they first established trade with Boston. Contributing to the spread of polydactyl cats by this means,

sailor A sailor, seaman, mariner, or seafarer is a person who works aboard a watercraft as part of its crew, and may work in any one of a number of different fields that are related to the operation and maintenance of a ship. While the term ''sailor'' ...

s were long known to value polydactyl cats especially for their extraordinary climbing and hunting abilities as an aid in controlling shipboard

rodent Rodents (from Latin , 'to gnaw') are mammals of the Order (biology), order Rodentia ( ), which are characterized by a single pair of continuously growing incisors in each of the upper and Mandible, lower jaws. About 40% of all mammal specie ...

s. Some sailors thought they bring good luck at sea. The rarity of polydactyl cats in Europe may be because they were hunted and killed based on superstitions about witchcraft. Genetic work studying the DNA basis of the condition indicates that many different mutations in the same ZRS area can all lead to polydactyly. Author

Ernest Hemingway Ernest Miller Hemingway ( ; July 21, 1899 – July 2, 1961) was an American novelist, short-story writer and journalist. Known for an economical, understated style that influenced later 20th-century writers, he has been romanticized fo ...

became a famous aficionado of polydactyl cats after a ship captain gave him a six-toed cat that he named Snow White. Upon Hemingway's death in 1961, his former home in

Key West, Florida Key West is an island in the Straits of Florida, at the southern end of the U.S. state of Florida. Together with all or parts of the separate islands of Sigsbee Park, Dredgers Key, Fleming Key, Sunset Key, and the northern part of Stock Islan ...

, 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). Because of his love for these animals, polydactyl cats are sometimes referred to as "Hemingway cats".

Naming

Nicknames for polydactyl cats include ''Hemingway cats'', ''mitten cats'', ''conch cats'', ''boxing cats'', ''mitten-foot cats'', ''snowshoe cats'', ''boston-toed cats'', "providence cats", ''thumb cats'', ''six-fingered cats'', and ''Cardi-cats''. Two specific breeds recognized by some cat fancier clubs are the American Polydactyl and Maine Coon Polydactyl.

Breeding

American Polydactyl cats are bred as a specific cat breed, with specific physical and behavioral characteristics in addition to extra digits. The American Polydactyl is not to be confused with the pedigree Maine Coon Polydactyl. The polydactyl form of the Maine Coon is being reinstated by some breeders.

Genetics

In the case of preaxial polydactyly of the Maine Coon cat (Hemingway mutant) a mutation of the cis-regulatory element ZRS (ZPA regulator sequence) is associated. ZRS is a noncoding element, 800 kilobasepairs (kb) remote to the target gene SHH. An ectopic expression of SHH is seen on the anterior side of the limb. Normally SHH is expressed in an organiser region, called the zone of polarizing activity (ZPA) on the posterior limb side. From there it diffuses anteriorly, laterally to the growth direction of the limb. In the mutant mirroring smaller ectopic expression in a new organiser region is seen on the posterior side of the limb. This ectopic expression causes cell proliferation delivering the raw material for one or more new digits. 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 Hemingway (''Hw'') mutant tends to mostly induce extra fingers in the fore limbs, many other mutations affect the posterior limbs too. Polydactyly is a spontaneous complex phenotypic variation, developed in one generation. In the concrete preaxial form of the Hemingway (''Hw'') mutant the variation is induced by a single point mutation in a noncoding cis-regulatory element for SHH. In an extensive phenotypic variation like this, one or more complete digits at each single limb are developed including nerves, blood vessels, muscles and ligaments. The physiology of the digits can be perfect. This complex phenotypic result cannot be explained by the mutation alone. The mutation can only induce the variation. In the consequence of the mutation, thousands of events, each different from the wildtype, occur on different organisation layers, such as expression changes of other genes, cell-cell signal exchange, cell differentiation, cell and tissue growth. The summarized small random changes on all layers build the raw material and the process steps for the generation of the plastic variation. The mentioned form of polydactyly of the Hemingway 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 A polyphenic trait is a trait for which multiple, discrete phenotypes can arise from a single genotype as a result of differing environmental conditions. It is therefore a special case of phenotypic plasticity. There are several types of polyphen ...

) 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.

References

External links

Owner's appeal over cat's 26 toes
{{Domestic cat Cat health Congenital disorders of musculoskeletal system Supernumerary body parts Toes