101 
Effect of Karlodinium Micrum Toxin on Success of the Parasitic Dinoflagellate Amoebophyra SP.

Abstract

Parasitic dinoflagellates of the genus Amoebophrya infect and kill bloom‐forming dinoflagellates, including the toxic species Karlodinium micrum. Unlike non‐toxic hosts, K. micrum is partially resistant to infection, a trait that may be related to toxin production. Here we tested the hypothesis that parasitism of K. micrum is inversely related to toxin concentration in the culture medium. Time‐course studies were conducted to determine the influence of extracted toxin and toxin carrier (methanol) on host growth, parasite prevalence, and parasite load. Results indicate that methanol concentrations below 0.1% have no effect on these variables. When methanol concentration was maintained below 0.1%, extracted toxin equivalent to 100 to 10,000 K. micrum per ml had no effect on host abundance. We are currently analyzing sample to assess the fate of Amoebophrya dinospores when exposed to K. micrum toxin. We will also consider the effect of intracellular host toxin on parasite success, by examining the fate of Amoebophrya dinospores when inoculated to K. micrum cultures that express different levels of toxin production. Understanding the effect of toxins on parasite success will contribute to our knowledge of host‐parasite biology and provide insight into the role of dinoflagellate toxins as a defense against parasitism.