Question about two of my crocea clams

[anonome]

Hello all, I have two crocea clams that have been with me for almost two years. They were both much, much smaller when purchased.
My question is this......One of the clams on the left side of the tank seems to always have a widened opening, almost gaping, and I can see its gills (first pic). It reacts to light, and fish swimming by. Nothing in the tank is bothering it. I am enclosing a pic of the other crocea (second pic) that is maybe a foot away from it that appears to always have a closed opening.
I am not really too concerned with the left side crocea, because it has done this from the beginning, just very curious why it should be this way, and the other one that was purchased at the same time and growing in the same speed be so much different.
Is this something to be concerned about in the long term? I do feed the tank marine snow once a week, and the perameters are all where they should be.
I have been blessed with a very thriving tank, all is well with the fish and coral....Knock on wood, but inquiring minds what to know. Thanks in advance.

 

[nano reefer]

they both look fine to me.

 

[candycane]

I'm probably going to do a write up about gapeing in the next few days. I doesn't look like the top clam is really gapeing either. Have you had it under halides for the entire time up that high? The only thing that I am wondering is about the visible "veins" that are white and running across the mantle. It just looks like it might have some localized bleaching a wee-bit. Could be from the Frogspawn or Hammer or whatever that is on the lower right.

 

[anonome]

Thanks for the quick reply candycane. Good eye, the one clam does have some stress lines on it from a clone RBTA that was wandering the tank and planted itself right under the clam. I waited a few days to see if the RBTA would move on its own, it of course, did not. I moved the rock that the left side crocea is on over slightly and it seems to be much happier. This happened about 2 wks ago. The torch and the frogspawn do not touch the clam. I really think it got the stress marks from the RBTA.
Both clams have always been this high up in the rocks, but the halides were added a year ago in April. Some negative response was noticed at first, but has since rectified itself. If the clam is looking good then that is all I really wanted to hear, but of course, if it needs anything I will help it out. Thanks again.