Why is the skin so rough?

[Kwazy]

Hi,
Today, I was rearranging a plant in my tank and my little girl (a motoro) came to investigate my arm. I just let her touch it as I didn't want to jerk away and scare her.

Though her underside was very soft, her topside was extremely rough. It felt almost like wet sandpaper. were all of the little bumps sensors of some kind or something? or just rough? Is this normal?

Thanks.

 

[Gshock]

Denticles. Like sharks, rays have skin that feel like sandpaper. If you brush in the direction the denticles are pointing, then it feels smooth, if you brush the other way, it feels rough.

 

[Kwazy]

thanks.

 

[Zoodiver]

Spot on. The design gives them a couple of things.
First off, the interlocking nature of those denticles gives them a psuedo chainlink armor for protection. It also makes them hydrodymamic - low friction in water. That is why they feel smooth rubbing front to back, but course rubbing back to front. Less friction means less work to move... translating to enegry conservation for them.
Denticles are like small triangular teeth coating the outter surface of elasmobranch species.

 

[DavidW]

here ya go

http://www.sharkskincoating.com/newse.asp?newsid=242

or

http://www.ivanhoe.com/science/story/2005/05/05si.html

 

[Kwazy]

Cool

 

[lincolngoh]

I'm throwing in my 2 cents that it's It because they like rough sex. The tough skin lessens the damage done & mortality done when males are clamping onto the females with their jaws.

 

[jakezori]

"why is the skin so rough" thats what she said---

As far as I know it depends on the stingray. Maybe too many people were touching it and it lost its slime coat.