Solved Pinched mantle syndrome and a success story

So I thought I would relay my experience with a recent clam purchase and some problems I encountered with pinched mantle syndrome.

Two weeks ago I picked up a beautiful 1.5" ultra maxima from Bronsons' fish in Iowa City. He had just gotten in an order of clams from ORA, and I picked this one up shortly after it arrived since I've been wanting a centerpiece for my reef.

On day one it looked like this:


Notice the two small 'pinches' on the bottom left rim of the clam's mantle.
I left for a couple days and came back to a very sick clam. Unfortunately I don't have any pictures, but suffice it to say it was bad. The mantle was completely withdrawn on 1/3rd of the clam, by the next day half of the mantle was in poor shape. Following extensive research online, I learned that pinched mantle syndrome is most often a result of a protzoan parasite in the clam's tissue that can become fatal if the clam becomes stressed (e.g. shipping stress) (Citation).

There are mixed remedies out there, but one that seems fairly common is a freshwater dip. Now, I've always thought that clams and other invertebrates don't tolerate salinity swings at all--much less an extended bath in a hyposaline environment. With no other options I performed a 30 minute bath in temperature and pH corrected DI water before the lights went out. The next morning the clam looked visibly better, but by the end of the day it was looking bad again. Two more 20' FW baths over the next 24 hours and by the next day the clam was looking a lot better. Two days later and the clam is looking good as new.

So, if you happen to get a sick clam, give freshwater dips a try. I was sure that it was going to kill the clam, but by golly it did the trick.