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Do sharks have placoid scales?

  1. Nov 10, 2014 #1
    Where placoid scale is present in chondrichthyes ,?i looked on specimen of shark fish ,but did not find any placoid scale neither in external anatomy nor in internal anatomy ."
     
  2. jcsd
  3. Nov 11, 2014 #2
    Generally scales grow from the dermal layer, I suppose.

    I don't know if there is a similar rule that helps predict where it is absent as a dermal cover.
     
  4. Nov 11, 2014 #3

    jim mcnamara

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    Shark skin feels like sandpaper. The denticles (placoid scales) are pretty small, but you can feel them.
    You have to "pet" the shark moving your hand from the tail toward the head. Be careful, it will clobber your skin.
    They are very sharp, and they have an extremely hard (vitrodentine) layer on the outside, with a fine point.

    Swimmers who have encountered harmless sharks have sometimes gotten what looks like road rash - a big abrasion - from rubbing the shark the wrong way, so to speak. Pat your specimen and see. Carefully.... sharks make terrible cuddle pets.
     
  5. Nov 11, 2014 #4
    oh you mean as placoid scale are really small we can not see them and can only feel.
     
  6. Nov 12, 2014 #5

    jim mcnamara

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    They are tiny little prickly points "aimed" toward the tail. In science terms retrorse projections. They are felt by touching only from 3 feet away. Too small to see. Try: Get a magnifier (like 10x or more) and get up close and personal with the shark specimen. Like inches away. The specimen is preserved (not alive), right? I hope so.
     
  7. Nov 12, 2014 #6

    Evo

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    The Japanese make food graters from shark skin, it's that rough and durable.
     
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