kastanzaman,
Hopefully you did a nice slow acclimation for your new clam, but it isn't at all unusual for a clam to show some stress at being transferred to a new tank. Yes, that is gaping, though not as bad as I've seen it in some cases. If it is responding well to movement and shadows, just give it some time to adjust and it may be fine. I'd suggest putting a small flat rock or clam shell under the sand for it to attach to if it wants and messing with it as little as possible for a while.
To be safe, double check your water parameters are all within good reef tank tolerances, and if your lighting is significantly stronger than the tank it came from, a layer or two of screen over that section of the tank for a little while would help it get used to its new brightness.
The colors are lovely! Best of luck.