Parasitic Life Styles of Marine Dinoflagellates
COATS, D. WAYNE
Journal of Eukaryotic Microbiology, Volume 46, Issue 4, July 1999, Pages 402–409
[…]parasitic dinoflagellates exhibit varying degrees of host specificity. The fish ectoparasite Amyloodinium ocellatum shows almost no host preference, with infections reported for over 100 species representing more than 40 families of fish (Lom 1981). Amyloodinium ocellatum has even been reported as a hyperparasite of a trematode parasite on the skin of [fish].
Attempts to transmit A. ocellatum [velvet] experimentally, however, suggest that some fish may not be susceptible to infection or become resistant with age (Lawler 1980). Most of these less susceptible host species are able to tolerate very low oxygen concentrations or to produce large amounts of mucus that may prevent attachment of the parasite.
What are these guys doing when they aren’t parasitizing fish…?
[There are] species known to attack the following organisms: (1) marine protists, including diatoms[…]; (2) eggs of rotifers, copepods, euphausids, shrimp, and fish[…]; ( 3 ) adult and/or juvenile hydromedusae, siphonophores, ctenophores, annelids, chaetognaths, appendicularia, and fish (by Amyloodinium ocellatum[…]); and (4) the parasitic trematode Neobenedenia melleni (by Amyloodinium ocellatum); see references for Table 1.
They appear to stay busy even if no fish are around.
You can see how crazy parasites can get in the related article, Hyperparasitism of trichodinid ciliates on monogenean gill flukes of two marine fish, when they’re in a completely unhealthy, unnatural setting. In this case, “velvet” dino’s that were found to be infecting flatworms on a fish….a parasite on a parasite: