Question about crab shells?

[chrisw74]

My empty hermit crap shells are falling apart you can see where there are holes in them. What would cause that and what can I do to prevent this?

 

[snowrider84]

i think it just happens i wouldnt worry about it, the ones in my tank do the same

 

[sickboy]

I haven't noticed any of mine do this, but it is just probably normal break down of material.