Well he definitely is a derasa or has derasa in him. I've been doing some more research about it and I have seen similar morphs. I have found no scientific articles about definitive hybridization of tridacna clams although at least one mentioned that it may be possible. I also understand skinz opinion about the possibility that there might not be hybridization at all. Having read several articles that do suggest that hybridization is possible, I'm going to remain open to the fact that it may or may not be possible. In terms of this specific clam, he is gaining color back quickly and now has clearly visible, short, brown stripes that the more common dress have. Also, the more the "holes" color up the more we will be able to see if they are similar to those of T. gigas but for now they do not. The only thing that leaves me wondering, is how do we know that the morph with the holes is not a hybrid? We really couldn't know without some sort of DNA testing and comparison with known derasa and known gigas. I will see about a new picture to show how he is recovering.
reefsponge- during my own research I found a few other photos of a morph exactly like the one you posted. I am certain that the clam I have is the same morph, I'm just not convinced either way as to what it really is.