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gracy
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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 ."
oh you mean as placoid scale are really small we can not see them and can only feel.jim mcnamara said: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.
Yes, all sharks have placoid scales. These scales are a defining characteristic of the shark species and are present on all parts of the shark's body, including the fins and tail.
Placoid scales are made of a hard, enamel-like material called dentin, which is similar to the material found in human teeth. They are also covered in a layer of hard, enamel-like material called enamel, which helps to protect the scales from damage.
Placoid scales serve several functions for sharks. They provide protection against predators and help to reduce drag as sharks swim through the water. They also play a role in sensory perception, allowing sharks to detect changes in water pressure and movement.
No, placoid scales are not unique to sharks. They are also found on other cartilaginous fish such as rays and chimaeras. However, placoid scales are much larger and more numerous on sharks compared to other species.
No, not all sharks have the same type of placoid scales. While most sharks have small, overlapping scales, some species have larger, non-overlapping scales. In addition, some species have modified scales that serve a specific function, such as the thorn-like scales found on the skin of the thresher shark.