Effects of toxic dinoflagellate Alexandrium minutum on the expression of detoxification-related genes in the marine copepod Tigriopus japonicus

To understand the effects of the toxic dinoflagellate Alexandrium minutum on the marine copepod Tigriopus japonicus, we assessed acute toxicity and swimming behavior (swimming speed, swimming distance, and swimming path trajectory) in response to A. minutum exposure. No significant changes in survival and swimming behavior were observed in response to A. minutum. Therefore, to validate the effects of A. minutum on the molecular defense response of T. japonicus, we measured mRNA expression levels of detoxification-related genes (phase I cytochrome P450s [CYPs], and phase II glutathione-S transferases [GSTs]) in response to A. minutum. The mRNA expression levels of these detoxification-related genes (CYPs and GSTs) were significantly up-regulated and down-regulated (P < 0.05) in response to A. minutum. In particular, CYP3024A2 and GST-Theta3 showed significant up-regulation. Overall, these results suggest that CYP and GST genes are likely to play crucial roles in detoxification mechanisms in T. japonicus, resulting in no significant changes in the survival and swimming behavior of this marine copepod in response to A. minutum exposure.