Abnormal Derasa Mantle

[OrionN]

Of all the years and the clams I keep I never seen a mantle that is indented in like this mantle of my Derasa.
I got him several months ago from Petco. I notice the abnormality but assumed that it is due to shipping stress and did not think much of it. Now after several months, growing well, the abnormality persists. I wonder if any reefers with Tridacna clams, of any species with similar looking mantle.
In the picture below the sunken area on the mantle is clearly seen. It sorta look like skull eye spots or scream face mask.
Anybody?

It is growing well

 

[minus9]

Yeah, that is kinda strange. But like most living things, genetics can be funky sometimes. I've seen pictures of clams with multiple exhalant siphons. I've also seen clams with "crinkled" mantles, which is really funky.

 

[Scorpius]

I have two deresa that do this and one that doesn't.