Pinched Mantle

[twisty]

Hi!
I've had this clam well over 2years.
It was doing fine up to last night.

Noticed the Mantle shrivled up within it's shell.
I have since changed it's location...No difference.
I have checked for the Piramid Snails.None on the Clam
I have burped it.. in case air within... No diffence.
Can someone confirm this is a pinched mantle?

I hope it recovers...Wouldn't want to lose it.