A polydactyl cat is a cat with a congenital physical anomaly called polydactyly (or polydactylism, also known as hyperdactyly), that 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 (in the United States and Canada) and in South West England and Wales.
Video Polydactyl cat
Occurrence
True polydactyly is a congenital abnormality, genetically inherited as an autosomal dominant trait of the ZRS cis element of the Pd gene with incomplete penetrance.
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 eight digits on their front and/or hind paws. Both Jake, a Canadian polydactyl cat, and Paws, an American polydactyl cat, were recognised by Guinness World Records 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.
Feline radial hypoplasia (see squitten) is a mimic of polydactyly and is considered a severe condition. Radial hypoplasia may cause the formation of extra jointed toes, but it is not a result of the gene normally associated with polydactyls. It thus does not cause the "mitten cat" or "thumb cat" condition where the extra toes occur separated from the normal ones just like a dewclaw, usually associated with an additional pad which makes them look like an underdeveloped foot sticking out near the base of the normal toes. Rather, radial hypoplasia-related extra toes are immediately adjacent to the normal ones, giving the cat overly large, flat feet -- colloquially known as "patty feet" or "hamburger feet". Though this looks less serious than true polydactyly (as the feet appear "normal" apart from having one or two extra toes), breeding such cats will eventually result in severely disabled offspring.
Maps Polydactyl cat
History and folklore
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 South West England, Wales and Kingston-upon-Hull. Polydactyl cats have been extremely popular as ship's cats. Although there is some controversy over whether the most common variant of the trait originated as a mutation in New England or was brought there from Britain, there seems to be agreement that it spread widely as a result of cats carried on ships originating in Boston, Massachusetts, and the prevalence 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, sailors were long known to value polydactyl cats especially for their extraordinary climbing and hunting abilities as an aid in controlling shipboard rodents. Some sailors thought they bring good luck at sea. The rarity of polydactyl cats in Europe may be because they were hunted and killed due to superstitions about witchcraft.
Genetic work studying the DNA basis of the condition indicates that many different mutations can all lead to polydactyly.
Nobel Prize-winning author Ernest Hemingway was a famous aficionado of polydactyl cats, after being first given a six-toed cat he named Snowball by a ship's captain. Upon Hemingway's death in 1961, his former home in Key West, Florida became a museum and a home for his cats, and it currently houses approximately fifty 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, 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, 800.000 basepairs 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.
Polydactyly is a spontaneous complex phenotypic variation, developed in one generation. In the concrete preaxial form of the Hemingway 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, i.e. 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) 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.
See also
- Polydactyly
- Polydactyly in early tetrapods
- Lil Bub and Paddles, notable polydactyl cats
References
Further reading
- Chapman, V. A.; Zeiner, Fred N. (1961). "The anatomy of polydactylism in cats with observations on genetic control". The Anatomical Record. 141 (3): 205-17. doi:10.1002/ar.1091410305. PMID 13878202.
- Danforth CH (1947). "Heredity of polydactyly in the cat". The Journal of Heredity. 38 (4): 107-12. PMID 20242531.
- Danforth, C. H. (1947). "Morphology of the feet in polydactyl cats". American Journal of Anatomy. 80 (2): 143-71. doi:10.1002/aja.1000800202. PMID 20286212.
- Jude, A. C. (1955). Cat genetics. Fond du Lac: All-Pets Books. OCLC 1572542.
- Lockwood, Samuel (1874). "Malformations". The Popular Science Monthly. Vol. IV. New York: D. Appleton and Company. p. 383.
- Robinson, Roy (1977). Genetics for Cat Breeders (2nd ed.). Elsevier. ISBN 978-0-08-021209-8.
- Sis RF, Getty R (1968). "Polydactylism in cats". Veterinary Medicine, Small Animal Clinician. 63 (10): 948-51. PMID 5188319.
- Todd NB (1966). "The independent assortment of dominant white and polydactyly in the cat". The Journal of Heredity. 57 (1): 17-8. PMID 5917255.
- Vella, Carolyn M.; Shelton, Lorraine M.; McGonagle, John J.; Stanglein, Terry W. (1999). Robinson's Genetics for Cat Breeders and Veterinarians (4th ed.). Oxford: Butterworth-Heinemann. ISBN 978-0-7506-4069-5.
- Wenthe, M; Lazarz, B (1995). "Ein Fall von atavistischer Polydaktylie an der Hinterextremität des Hauskatze" [A case of atavistic polydactyly at the hind limb of a cat]. Kleintierpraxis (in German). 40 (8): 617-9.
- Wittmann, F (1992). "Polydactylism in a Cat". Der Praktische Tierarzt. 73 (8): 709.
External links
- Hemingway Home Museum, Key West Florida, cats webpage
- Article on polydactylism in cats in New England
- Images of polydactyl cats
- PolyTrak: Maine Coon Polydactyl Tracking Database and Resource
- Owner's appeal over cat's 26 toes
Source of article : Wikipedia
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