Empty Shells

[67chevelle]

I have some nerite snails in most of my tanks.I'm not sure how many total,but I would say 15 to 20 in 3 different tanks.Over the last month or so,I have found 3 or 4 empty shells total in all 3 tanks.And have found 2 of the little rough patches on their foot that shuts them in their shell.Not sure what it is called,but I hope someone knows what that thing is and what I'm talking about.
Anyone have any ideas as to what is happening to my snails? Their shells are all in good shape,and all of the othere snails seem to be doing fine.

 

[NeonFlux]

Sometimes snails would hibernate for a while;they usually awaken later

 

[67chevelle]

They hibernate outside of their shell,and shed that little rough patch on their foot?

 

[soobie]

No, if you're seeing an empty shell and a loose operculum (the "trapdoor" that closes the shell), the snail has died. I'm not sure what the lifespan of a nerite in fresh water is; maybe they just lived out their time?

 

[67chevelle]

No, if you're seeing an empty shell and a loose operculum (the "trapdoor" that closes the shell), the snail has died. I'm not sure what the lifespan of a nerite in fresh water is; maybe they just lived out their time?

I have had them for awhile,less than 2 years though(i think).I'm not sure of their lifetime either.I new they had died,I just found it a little weird to find the operculum(thanks).Like I said,shells were all healthy,all the others look and seem fine,so maybe it was just their time.

Thanks for you help.