Tortoiseshell cat

A (long haired) tortoiseshell cat.

Tortoiseshell describes a coat colouring found mostly in female cats. Cats of this colour are mottled, with patches of orange or cream and chocolate, black or blue. They are sometimes called torties for short. The term “tortoiseshell” is typically reserved for cats with brindled coats that have relatively few or no white markings.

Those that are largely white with red and brown patches (rather than a brindled aspect) are described as tortoiseshell-and-white (in the United Kingdom) or calico (in Canada and the United States). Tortoiseshells and calicos are not specific breeds of cat. The tortoiseshell markings appear in many different breeds as well as in non-purebred domestic cats.[1] This pattern is especially preferred in the Japanese Bobtail breed.[2]

Patterns
Tortoiseshell cats have coats with patches of red, brown or black, chocolate, cream, or cinnamon. The size of the patches can vary from a fine speckled pattern to large areas of colour. Typically, the more white a cat has, the more solid the patches of colour. Dilution genes may modify the colouring, lightening the fur to a mix of cream and blue, lilac or fawn. The markings on tortoiseshell cats are usually asymmetrical. Occasionally tabby patterns of eumelanistic and pheomelanistic colours are also seen (these are often then called “tortie-tabby”, “torbie” or “caliby”). Tortoiseshell also can be expressed in the point pattern.

Genetics [Main article: Cat coat genetics]
Tortoiseshell and calico coats result from an interaction between genetic and developmental factors. The primary gene for coat colour (C) is located on the X Chromosome and has two co-dominant alleles, Orange (XO) and Black (XB), that produce orange phaeomelanin and black eumelanin pigments, respectively. The cells of female cats, which like other mammalian females have two X Chromosome (XX), undergo the phenomenon of X-inactivation, in which one or the other of the X-chromosomes is turned off at random in each cell in very early development. The inactivated X becomes a Barr body. Cells in which the chromosome carrying the Orange (XO) allele is inactivated express the alternative Black (XB) allele. Cells in which the Black (XB) allele is inactivated express the Orange (XO) allele. Pigment genes are expressed in melanocytes that migrate to the skin surface later in development. In bi-coloured tortoiseshell cats, the melanocytes arrive relatively early, and the two cell types become intermingled, producing the characteristic brindled appearance consisting of an intimate mixture of orange and black cells, with occasional small diffuse spots of orange and black.
In tri-coloured calico cats, a second gene interacts developmentally with the coat colour gene. This spotting gene produces white, unpigmented patches by delaying the migration of the melanocytes to the skin surface. There are a number of alleles of this gene that produce greater or lesser delays. The amount of white is artificially divided into mitted, bicolour, harlequin, and van, going from almost no white to almost completely white. In the extreme case, no melanocytes make it to the skin and the cat is entirely white (but not an albino). In intermediate cases, melanocyte migration is slowed, so that the pigment cells arrive late in development and have less time to intermingle. Observation of tri-colour cats will show that, with a little white colour, the orange and black patches become more defined, and with still more white, the patches become completely distinct. Each patch represents a clone of cells derived from one original cell in the early embryo.
Male cats, like other mammalian males, have only a single X chromosome (XY) that does not undergo X-inactivation: coat colour is determined by which allele is present on the X, and they will be either entirely black or orange. Very rarely (approximately 1 in 3,000[3]) a male tortoiseshell or calico is born. These animals typically have an extra X chromosome (XXY), a condition known in humans as Klinefelter syndrome, and undergo an inactivation process like that in females. As in humans, these cats are always sterile because of the imbalance in sex chromosomes. Some male calico or tortoiseshell cats may be chimeras, which result from the fusion in early development of two embryos with different colour genotypes. Others are mosaics, in which the XXY condition arises after conception and the cat is a mixture of cells with different numbers of X chromosomes.

Interesting facts
In looking at a calico cat’s skin, one can find evidence of its genetic make up. When the fur is parted, particularly in areas close to the nose and ears, the skin will be multi-coloured with darker spots of pigmentation in places where there is darker fur.[4]
On October 1, 2001, calico cats were named as the official state cat of Maryland.

Folklore
Cats of this colouration are believed to bring good luck in the folklore of many cultures.[5] In the United States, these are sometimes referred to as money cats.[6] The Japanese Maneki Neko figurine is almost always a calico cat.

See also

• [Fur]
• [Tama (cat)]
• [Cat coat genetics]

Photo Gallery

1. Syufy, Franny. “More Cat Colour Patterns: Calicos, Tortoiseshell, Tuxedo Cats“. Retrieved 2010-12-22
2. “Breed Profile: Japanese Bobtail”. Cat Fancier’s Association. Retrieved 2007-06-02
3. Spadafori, Gina. “Feline Fallacies”. The Pet Connection. VeterinaryPartner.com. Retrieved 2008-07-03
4. Smith, S.E. (2003). “What are Calico Cats?”. WiseGeek.com. Retrieved 2008 – 05-25
5. Hartwell, Sarah (1995). “Feline Folktails – Cats in Folklore and Superstition”. Retrieved 2009-01-22
6. Finegan, Edward; Rickford, John (2004). “Language in the USA: Themes for the Twenty-first Century”. Cambridge University Press. Retrieved 2009-01-22

External links

1. Wikimedia Commons has media related to: Tortoiseshell cats
2. Wikimedia Commons has media related to: Calico cats
3. Tortoiseshell and tri-colour cats
4. Calico cat
5. tortiecats.free.fr : website showing the diversity of tortie and calico coats

[Portions From Wikipedia, the free encyclopedia]