Stringy threads from maxima mantle

[Paleozoic_reefer]

I’ve noticed some clear threads coming from my maxima clam’s mantle. I first thought they were vermitid snails but it seems the clam is producing them (?). Is this clam byproduct or do I need to look for more vermitid snails on the clam?

 

[blaxsun]

Nice clam!

 

[OrionN]

Those strands are not from the clam mantle, but from the shells. It looks to me like they are dinoflagellate, Dino for short. One of the harder to get rid of nuisance algae.