Showing posts with label Tabby Siamese. Show all posts
Showing posts with label Tabby Siamese. Show all posts

Wednesday 31 August 2011

Siamese Cat Binocular Vision

The Siamese cat is well known for a squint and a kinked tail. Both have been bred out by breeders over the years as they are considered "defects" but they are nonetheless part of this cat breed's heritage. The kinked tail in cat show competition is reason to disqualify the cat as I recall.

There are colorful legends regarding the squint that are usually about Siamese cats who defended temples and valuables. The task was arduous and it caused the cats to develop a squint!

The question on some people's minds is, "does the Siamese cat squint affect normal vision and particularly binocular vision?" Let's first say that it isn't just Siamese cats that have squints but they have a genetic predisposition to acquiring the squint. The cat below is not a Siamese but has a clear squint. Perhaps she is a Siamese mix (lynx point)




Not Siamese but clear squint - Photo by fazen (Flickr)

Cats have two eyes to allow them to judge distance and depth. Two eyes give animals a form of three dimensional vision. This is important to cats in making judgements on tracking objects, jumping and hunting etc.

It transpires that the squint is apparently a compensation for defective wiring of the nerves that go from the eyes to the brain. In normal cats half the optical nerves cross over to the side of the brain opposite to the position of the eye. This provides binocular vision.

In Siamese cats the nerve fibres that were not meant to cross over, do in fact cross over. This causes "the faulty positioning of the retinal map on the tectum". The tectum is a region of the brain, specifically the dorsal part of the mesencephalon (midbrain). The squint cancels out the effects of the faulty positioning on the tectum by "altering the positioning of the retina".

So there you have it. The squint develops over the first six to eight weeks of the kitten's life to make this compensation.

Siamese cat binocular vision is maintained by the famous Siamese cat squint. That's how nature has compensated for a genetically inherited neurological defect. Incidentally, the Siamese and Persian cats have the most genetically inherited diseases and are two of the most long standing purebred cats.

The references are from the New Scientist Aug 17, 1972. Thanks to Google Books.

Monday 8 August 2011

Seal Point Siamese Cat in Thailand

This is an interesting photo of a Siamese cat in Siam - well it is called Thailand now but does this cat give us a clue as to what the original Siamese cat looked like before being picked up by the English cat fancy in the late 1800s.

The picture was taken where the marker in this map indicates:


View Larger Map

This is the photo:




Seal Point Siamese Temple Cat in Thailand

You can see that this cat is not oriental in shape but mid range moggie shape (semi-cobby) and a little fat actually!

Cat breeders in the USA justify breeding very slender cats on the basis that the shape is what the Siamese cat was like in Thailand - rubbish obviously. Or if they don't try and justify selective breeding in that way they are clearly breeding cats that are unnatural and unpopular with the public.

You can see the tabby banding on the forelegs. This cat has, it seems, an element of tabby pointing about him (lynx points).

Saturday 18 June 2011

Siamese Tabby Cat

The Siamese tabby cat is not tabby cat all over the body but just on the points - the extremities of the cat. What I mean is that the tabby coat only affects the points. Well that is not exactly true because I suspect the objective is to have the tabby gene only affect the points but it does affect to a certain extent other parts of the body.

lynx point Siamese Siamese tabby cat
Lynx point Siamese - Photo by ♥ellie♥

This creates a cat that in my opinion no longer looks like a Siamese cat but each to their own taste. You will see the classic "M" mark on the forehead or a vestige of it and banding on the legs and some lines on and around the face.

When the pointing is broken by the tabby gene it is less distinct. Tabby pointed Siamese cats are called Lynx point Siamese cats.

lynx point Siamese Siamese tabby cat
Lynx point Siamese cat - by AlishaV
Siamese tabby cats can be sliver tabby (silver lynx points) and tortie points. Although tortie or tortoiseshell points are not tabby points but the broken pointing looks similar.

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