Clam ID


Moving Money
Premium Member
Yes, I know, Tridacna sp., ha ha.
I bought this as T. Crocea. A visitor to my house, may he never darken my door again, said that it was not Crocea, but a lowly Derasa! Is this correct? Here's a photo open:
I'm no clam ID expert but I don't beleive it's T. derasa. If you told me it was T. maxima I'd beleive you. I'd even beleive T. crocea. Heck I might even beleive T. squamosa. But T. derasa ... no ... I know my T. derasa's ... the shell isn't quite right to be one of those. Methinks, anyhow, FWIW.
It's either a T. crocea or a T. maxima. It's probably a little to small to be certain. My money is on crocea.
My T. deresa shell is mostly very smooth with only 1 or 2 small scutes near the top edge.

It is obvious that your visitor doesn't know what he is talking about. IMO, it is most likely Crocea. Maxima also possible. It is not Gigas, Derasa or Squamosa. It is obvious that it is not a Gigas or Derassa. Regarding Squamosa, it is highly improbable because the mantel shape. Squamosa have a very wide and distinctive mantel, the area that is inside the shell and not expand out of the shell. This area is much wider than in Maxima or Crocea
beginner question here...
Is it possible to have a hybrid Maxima/Crocea?
I have a max and a crocea in my tank and this calam really resembles both.
Great looking clam, I remember the debate at the reef club meeting.
ridetheducati said:
My vote is for Maxi.

Maxi's have noticeable raised nipples on the mantle.

Can you get a shot of the excurrent?

I'll try to shoot it later today.
The sure way to tell a Maxima from a Crocea is looking at the opening for the for the foot of the clam. If it is a huge openning then it is a Crocea and a smaller but large openning then it is a Maxima. All the other points are not 100%.
Good point, but I dont think he can get a shot of the opening.

Any other ideas?

Lets rip out the byssal gland. Just kidding.
I will tell you for sure what kind it is just ship him to my house! There are no reported hybrids between maximas and croceas. There are reported hybrids between squamosas and maximas, derasas and maximas.
I still say maxima!
ridetheducati said:
Good point, but I dont think he can get a shot of the opening.

Any other ideas?

Lets rip out the byssal gland. Just kidding.

HEY HEY! Let's not carried away here.
Here's a closeup. There are definite structures (nipples?) on the mantle.
I got as good shots of the siphon as I could (not very). It is smooth. What are y'all looking for?