Interesting that there’s a test for dino’s!
Diagnosis of A. ocellatum has until recently relied on histology. To advance early detection of the parasite a PCR diagnostic was developed in the ITS2 region of rRNA. The test proved sensitive enough to detect 1 dinospore and 0.1 tomonts and will detect all available strains of A. ocellatum.
What drew my attention to this article is that I noticed a hobby magazine had mentioned something about “light sensitivity” in velvet.
Velvet is a type of dinoflagellate, and they are, in spite of claims of “light sensitivity”, apparently non-photosynthetic.
So I did some digging to see if there’s anything else to the claim and found the abstract for this thesis. (Unfortunately there’s no public access to the complete thesis, but there are good summary points in the abstract at least.)
Experiments to determine whether the pathogen employed chemotactic or phototactic responses for initial infection were undertaken. The behaviour of dinospores when presented with fish mucus and varying intensities and wavelengths of light was recorded. No response to either stimulus was observed.
So they are not photosynthetic, nor are they apparently phototactic.