Abstract
Chattonella marina and Heterosigma akashiwo are highly toxic red tide phytoplankton which causes severe damage to fish farming. Recent studies demonstrated that these flagellates release superoxide anion (O2-) under normal growth conditions. In the present study, we examined the effects of the fish mucus prepared from skin and gill of yellowtail, red sea bream, and japanese flounder on the production of 2- by the flagellates. All mucus tested stimulated C. marina and H. akashiwo to generate increased amounts of O2- in a concentration dependent manner. Thus, the common substances present in fish mucus of three species may be responsible for the stimulation of the flagellates. In the presence of 100μg/ml of each mucus, 4-6-fold increased level of O2- was detected in both flagellates. After the heat treatment (at 121°C for 15min), no significant decrease of stimulatory effects of the mucus was observed, suggesting that heat-stable components of the mucus may produce the stimulatory effect on the flagellates. Our results suggest the possibility that the fish mucus enhances the oxygen radical-mediated toxic effects of C. marina and H. akashiwo.
