clam with pinched mantle??

[christyf5]

Hi,

I got this clam a 3 weeks ago from J&L. It acclimated to the tank well and has been doing great but looking at it today its mantle looks a bit wrinkly to me. I did a search on RDO for wrinkly mantles and found I was perhaps using the wrong descriptor. I think maybe I have what they are calling a pinched mantle. Has anyone ever heard of this before or had any experience with it?? I think a FW dip was suggested in a thread on RDO but the clam returned to its pinched condition soon thereafter.

Here is a pic, note the pinched part in the middle compared to the "normal" mantle below it: