Question(s) of the Day: Symmetric Cats +


minlit asks:

Hey  Oldcat, I have a question. Is there a reason so many cats have a pretty good symmetry to their patterning?

Yes, there is a reason – almost all animals above the level of any complexity have an overall bilateral symmetry – basically the left and right sides are more or less identical as if reflected in a mirror down the centerline of the body.


When an embryo is tiny, it has little to no structure, no nerves, no blood vessels. Yet it needs to send ‘messages’ to parts of itself to ‘order’ the development.  This is done by chemical cues. As these cues spread out from the centerline where the nervous system is forming, they tend to do so with general symmetry, because the spreading has no reason to prefer left or right.  White Spotting is thought to occur because the cue to color the hair in skin cells does not reach the parts of the cat furthest from the head and spine.

So maybe we should be asking why a pattern is ever not symmetric?

Well one kind of pattern that is not symmetric is the X inactivation that produces tortoiseshell cats.  Female cats, like all female mammals, have two X chromosomes, while Males have only one – the second is the sex determining Y, which has no other genetic use. (Insert joke about useless parts on men here).  Since the cell is built for one X, the embryo must pick one or the other to use. This is essentially a random choice, so there is no symmetry needed.  This also means that females are genetically a mix of two different genetic patterns – some cells use one X, others the other. (Insert joke about females and being of two minds here).

minlit also asks:

Is it a myth, or are cats’ whiskers related to their girth? If so, what happens when a fat cat gets thinner? I’ve always wondered about that! D

I’ve heard the theory, but I don’t see how the whiskers could know how fat a cat was.  It is even hard to see how they could reliably be used to check the size of the head.  Also, if you look at it, cats hate to have their whiskers touch things, instead they fold them back if going into a tight space. They have good vision.

Plus, I have seen cats get their head stuck in things, so it doesn’t work all the time anyway.

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About Oldcat

Engineer with Cats
This entry was posted in Calpurnia, Cats, Genetics, Gustavus Adolphus, Julius Caesar and tagged , , , , , . Bookmark the permalink.

16 Responses to Question(s) of the Day: Symmetric Cats +

  1. Holy cow-spotted cat! I have so much to say that I don’t know where to begin… Firstly, my whiskers are as wide as my widest points and I get my head stuck in things daily. So the whiskers aren’t foolproof, even if they’re as long as the cat is fat…

    How asymmetrical does a cat have to be to be really asymmetrical? According to the Guide to Housecat Coat Colors and Patterns, “patches or swirls on a cat often look like pieces of a jigsaw puzzle that moved away from each other”. And that’s exactly what my driver’s side looks like. But my passenger’s side is very holstein-esque and has significantly less black fur. And my lower lip is half black and half pink…

    We’ve established that I’m a failed black cat. But does being as asymmetrical as I am also make me a failure of nature? I’ve read that females in all species look for mates that are symmetrical. So if I were a cat in the wild, would I be unable to find a mate to pass on my genetics? And what has to happen on an embryonic level to make a cat look like me?

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    • Lurkertype says:

      Dear Pedro:

      Don’t fret. My cat’s father was a very asymmetrical cow-kitty, like yourself. Yet he was the alpha-cat of the neighborhood for several years and got ALL the ladies. However, he didn’t tend to get his head stuck in things, so that might affect your romantic success.

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    • littlemiao says:

      I wouldn’t worry. Some of the most successful cats I know have been asymmetrical B&Ws (number 5, and of course Sprocket).

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    • Oldcat says:

      The bicolor lower lip is simple enough – the skin color follows the fur color, so black fur = black lip.

      The mating question is aslo simple. First, a female cat in heat is not very particular, to give a good mix of kitten genes. And it is by no means a sure thing that cats see the same way we do – they don’t notice still things well and tend to lock on to movement – so the symmetry of the pattern might not be high on the list.

      I did see the ‘tearing’ theory on the poster and was interested, but obviously not all spotting patterns are developed that way, as the symmetry is usually pretty good for low levels of spotting. Since my theory is that high levels of spotting are caused by the lockdown happening earlier in development, it could be that there is a time when not all of the final skin cells are on the ‘outside’ of the cat. If the inside group is white, and the outside group is colored, then the migration of the two type to the skin could ‘break up’ the colored regions. Another way would be if some cells are better dividers than others – so a symmetric pattern gets uneven because parts of it spread faster than other neighboring areas, warping the original significantly.

      Calpurnia’s blaze looks kind of like this – as if a symmetric A was tugged to the left around the eye region. But otherwise she is pretty symmetric.

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      • It’s really interesting to think of all the things that have to happen to build a basic cat, isn’t it? I’m not sure I really understand the process, but I feel like I’m getting close now. 🙂

        Good point on the mating. I can’t tell the difference between a cobra and a power cord in daylight, so how is a female cat going to know me from Lotus Miao?

        One final scary question… Is my skin black under my black spots? My human has always wanted to shave me to see, but so far she’s restrained herself…

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      • minlit says:

        Pedro you’re a hoot! The cobra and light cord brought tears to my eyes! Best line I’ve read today!

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  2. minlit says:

    Thank you Old Cat – you have filled one of the many gaps in my knowledge. Well, two if you count the whiskers!
    As for Pedro, I would say only this: Failure is always measured against other people’s standards. You can and should measure success for yourself, though I’d say world domination via your blog is a pretty good place to start!

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  3. I do know that I am a fabulous cat, and I will be successful in my professional endeavors. As a neutered indoor pet, I know that my genetic makeup and/or anything that happened at the embryonic stage doesn’t really matter. But I’ve always looked like 2 different cats, so I’m curious to know why! 🙂

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  4. littlemiao says:

    Fascinating! I love this question. I have wondered why Sprocket is so asymmetrical and Chun is so perfectly symmetrical. I guess Sprocket was sprocketting around too much in utero so his white spots didn’t know up from down.

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  5. I inserted both jokes, and enjoyed my humor immensely! I can attest that John’s whiskers do NOT match his girth. Far from it! heh heh.

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  6. I seem to be unable to nest this comment up there by the photo link, so here’s my reply to that:

    Oh my.

    Like

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