Clam biology question

[Palmer]

Hi,

I bought a Tridacna Crocea a couple of weeks ago (about 4 " across) and I noticed a long thin string/tentacle about 1-2" the same color as the mantle (blue purple) coming out of what I believe to be the exhalent siphon. I was looking at diagrams on clam biology and reading about the small tentacles they have, but I couldn't find anything like I was seeing in any articles I have looked at so far.

Are they supposed to have something like this? I have only seen it come out when the halides are off and while it is just actinic lighting.

Palmer